O subgiant stars
created: 2016-11-02T18:47:41.000Z
modified: 2018-02-06T18:12:32.000Z
contributor: AAS Frey.Katie
creator: AAS Frey.Katie
type: Concept
alternative label: O subgiants
broader: O stars
broader: Subgiant stars
alternative label: O-type subgiant stars
alternative label: O-type subgiants

Parallel field
created: 2016-11-02T13:41:33.000Z
creator: AAS Frey.Katie
type: Concept
broader: Field of view

B subgiant stars
created: 2016-11-02T18:47:51.000Z
modified: 2018-02-06T18:08:34.000Z
contributor: AAS Frey.Katie
creator: AAS Frey.Katie
type: Concept
alternative label: B subgiants
broader: B stars
broader: Subgiant stars
alternative label: B-type subgiant stars
alternative label: B-type subgiants

Star forming regions
created: 2016-11-02T13:48:20.000Z
creator: AAS Frey.Katie
type: Concept
broader: Star formation
alternative label: Star formation regions
modified: 2020-11-04T16:42:35.183Z
contributor: AAS Frey.Katie Admin
definition: A region in the interstellar medium where processes of star formation are going on or have occurred in the past.
modified: 2020-11-04T16:42:46.647Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T16:42:46.615Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Blank fields
created: 2016-11-02T13:41:45.000Z
modified: 2018-09-13T19:35:12.000Z
creator: AAS Frey.Katie
type: Concept
broader: Field of view
contributor: AAS Frey.Katie
alternative label: Blank field

Blue compact dwarf galaxies
created: 2016-11-01T17:29:34.000Z
creator: AAS Frey.Katie
type: Concept
broader: Compact dwarf galaxies
modified: 2020-10-26T20:18:37.095Z
definition: An small irregular galaxy undergoing violent star formation activity. These objects appear blue by reason of containing clusters of hot, massive stars which ionize the surrounding interstellar gas. They are chemically unevolved since their metallicity is only 1/3 to 1/30 of the solar value.
contributor: AAS Frey.Katie
modified: 2020-10-26T20:20:33.677Z
editorial note: Definition Provenance
  created: 2020-10-26T20:20:33.649Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Y dwarfs
created: 2016-11-02T16:04:07.000Z
creator: AAS Frey.Katie Admin
type: Concept
alternative label: Y dwarf stars
broader: Brown dwarfs
alternative label: Y-type brown dwarfs
alternative label: Y brown dwarfs
contributor: AAS Frey.Katie Admin
definition: A type of ultra-cool brown dwarf with an effective temperature lower than 500 K. Near infrared spectra of these objects show deep absorption bands of H_{2}O and CH_4. So far only seven brown dwarf candidates belonging to this class have been found, all Y0 subtypes. These objects are very dim, with H magnitudes 19-23. The precise definition of the Y class requires new findings in the future about these objects.
preferred label: Y dwarves
modified: 2021-09-27T15:42:16.086Z
modified: 2020-11-04T20:58:47.692Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T20:58:47.664Z

DZ stars
created: 2017-01-23T19:32:01.000Z
creator: AAS Frey.Katie
type: Concept
broader: White dwarf stars
definition: A white dwarf whose spectrum shows metal lines only; no H or He.
contributor: AAS Frey.Katie Admin
alternative label: DZ white dwarf
alternative label: DZ white dwarf stars
modified: 2020-11-04T21:17:06.121Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-09T21:28:08.818Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T21:28:08.847Z

DQ stars
created: 2017-01-23T19:34:10.000Z
creator: AAS Frey.Katie
type: Concept
broader: White dwarf stars
definition: A white dwarf whose spectrum shows carbon features of any kind.
contributor: AAS Frey.Katie Admin
alternative label: DQ white dwarf
alternative label: DQ white dwarf stars
modified: 2020-11-04T21:16:34.709Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-09T21:27:38.780Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T21:27:38.817Z

Shell stars
created: 2017-01-23T20:12:14.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Chemically peculiar stars
definition: A main-sequence star, usually of spectral class B to F, whose spectrum shows bright emission lines superimposed on the normal absorption lines. The emission spectrum is explained by the presence of a circumstellar shell of gas surrounding the star at the equator. Shell stars are fast rotators.
modified: 2020-11-04T14:48:28.033Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:48:43.216Z
editorial note: Definition Provenance
  created: 2020-11-04T14:48:43.179Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Transient sources
created: 2017-03-20T21:12:29.000Z
creator: AAS Frey.Katie
type: Concept
broader: High energy astrophysics
narrower: X-ray transient sources
narrower: Gamma-ray transient sources
narrower: Ultraviolet transient sources
contributor: AAS Frey.Katie
narrower: Radio transient sources
related: Time domain astronomy
modified: 2019-11-25T18:33:08.387Z

X-ray transient sources
created: 2017-03-20T21:13:51.000Z
creator: AAS Frey.Katie
type: Concept
broader: Transient sources
narrower: X-ray bursters
broader: X-ray sources
related: X-ray bursts
alternative label: X-ray transient
contributor: AAS Frey.Katie Admin
definition: An X-ray source that enhances its emission well above its usual level for a period typically longer than a week. Recurrences can be periodic or aperiodic, but there is no obvious correlation between recurrence time and the luminosity amplitude of the outburst. X-ray transients seem to be divided into two classes: those associated with high-mass X-ray binary (HMXB) stars and those associated with low-mass X-ray binary (LMXB) stars. The HMXBs contain a neutron star or black hole paired with a massive star. Often, the stellar companion is a Be star, Be star, which sometimes sheds material from its equatorial region. In these systems, the transient event is characterized by having more higher energy X-rays in the spectrum. The LMXBs contain a neutron star or black hole orbiting around a cooler, low-mass star. These transient events often generate more lower-energy X-rays.
modified: 2020-11-04T21:03:21.663Z
modified: 2020-11-04T21:03:34.440Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:03:34.414Z

Gamma-ray transient sources
created: 2017-03-20T21:14:14.000Z
creator: AAS Frey.Katie
type: Concept
broader: Transient sources
alternative label: Gamma ray transient sources
alternative label: Gamma-ray transient source
broader: Gamma-ray sources
narrower: Gamma-ray bursters
related: Gamma-ray bursts
alternative label: Gamma ray transient source
contributor: AAS Frey.Katie Admin
alternative label: γ-ray transient source
alternative label: γ-ray transient sources
modified: 2020-12-17T16:32:27.013Z

Ultraviolet transient sources
created: 2017-03-20T21:14:27.000Z
creator: AAS Frey.Katie
type: Concept
broader: Transient sources
alternative label: UV transient sources
broader: Ultraviolet sources
contributor: AAS Frey.Katie
modified: 2019-11-26T19:48:13.168Z

Compact dwarf galaxies
created: 2016-11-01T14:35:49.000Z
modified: 2016-11-01T14:36:10.000Z
contributor: AAS Frey.Katie
creator: AAS Frey.Katie
type: Concept
broader: Dwarf galaxies
narrower: Blue compact dwarf galaxies
narrower: Ultracompact dwarf galaxies

Amorphous irregular galaxies
created: 2016-11-01T17:43:30.000Z
modified: 2018-05-10T15:01:07.000Z
alternative label: Type II irregular galaxies
creator: AAS Frey.Katie
type: Concept
alternative label: Irregular II galaxies
broader: Irregular galaxies
contributor: AAS Frey.Katie Admin

Exoplanet systems
created: 2016-11-01T14:33:14.000Z
creator: AAS Frey.Katie
type: Concept
broader: Exoplanet astronomy
definition: A planetary system consisting of exoplanets orbiting a star other than Sun.
related: Solar system
modified: 2020-12-09T19:41:38.101Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:02:59.376Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T21:02:59.346Z

High latitude field
created: 2016-11-02T13:41:57.000Z
creator: AAS Frey.Katie
type: Concept
broader: Field of view

Low surface brightness galaxies
created: 2016-11-01T17:58:24.000Z
creator: AAS Frey.Katie
type: Concept
alternative label: LSBG
broader: Galaxies
narrower: L galaxies
definition: A member of a particularly faint population of galaxies with a central surface brightness below the brightness of the background sky. The central regions of many of them resemble a dwarf galaxy, but most of the mass is contained in a large gaseous disk of low density that is observable only with long-exposure optical images or at radio wavelengths. Some are as massive as a large spiral galaxy, for example Malin 1. The proportion of LSBGs relative to normal galaxies is unknown. They may however represent a significant fraction of mass in the Universe. LSBGs are thought to be primitive systems because they have total masses similar to normal galaxies, but have typically converted less than 10% of their gas into stars. Spiral LSBGs do not obey Freeman's law.
contributor: AAS Frey.Katie Admin
alternative label: Ultra-diffuse galaxies
alternative label: Ultradiffuse galaxies
alternative label: Ultradiffuse galaxy
alternative label: Ultra-diffuse galaxy
alternative label: Ultra diffuse galaxies
alternative label: Ultra diffuse galaxy
alternative label: UDG
modified: 2020-11-09T21:21:55.076Z
modified: 2020-11-03T16:48:15.228Z
editorial note: Definition Provenance
  created: 2020-11-03T16:48:15.198Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Astronomy software
created: 2018-01-26T16:15:56.000Z
contributor: AAS Frey.Katie
creator: AAS Frey.Katie Admin
type: Concept
broader: Computational astronomy
narrower: Astronomy web services
narrower: Astronomical simulations
narrower: Software documentation
narrower: Educational software
narrower: Software licensing
definition: A general term used to describe a collection of computer programs, procedures, and documentation that perform some astronomy related tasks on a computer system.
modified: 2020-10-26T18:56:16.952Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T18:56:27.292Z
modified: 2020-10-26T18:56:27.321Z

Astronomy web services
created: 2018-01-26T16:16:21.000Z
modified: 2018-08-27T19:29:43.000Z
narrower: Virtual observatories
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy software
contributor: AAS Frey.Katie

Astronomical simulations
created: 2018-01-26T16:16:51.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy software
narrower: Hydrodynamical simulations
narrower: Magnetohydrodynamical simulations
alternative label: Astronomy simulations
narrower: N-body simulations
narrower: Radiative transfer simulations
definition: The construction of a mathematical model to reproduce the characteristics of an astronomical phenomenon, system, or process, often using a computer, in order to infer information or solve problems.
modified: 2020-11-05T15:24:38.693Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T15:24:51.142Z
editorial note: Definition Provenance
  created: 2020-11-05T15:24:51.111Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Astronomy data analysis
created: 2018-01-26T16:17:28.000Z
modified: 2018-08-27T19:34:56.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie
narrower: Astronomy data acquisition
narrower: Astronomy data reduction
broader: Computational astronomy
narrower: Astronomy data modeling
narrower: Astronomy databases
narrower: Astronomy data visualization
narrower: Astronomy data sonification
narrower: Astronomy image processing

Astronomy data modeling
created: 2018-01-26T16:18:47.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy data analysis
preferred label: Astronomy data modelling
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:41:59.403Z

Astronomy data acquisition
created: 2018-01-26T16:22:02.000Z
modified: 2018-08-27T19:26:19.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy data analysis
contributor: AAS Frey.Katie

Astronomy data reduction
created: 2018-01-26T16:22:15.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy data analysis
definition: The process of converting crude observational data into usable information for scientific interpretation, by correcting, rearranging, ordering, and simplifying.
modified: 2020-11-03T21:16:32.263Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:16:57.914Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:16:57.887Z

Software licensing
created: 2018-01-26T16:22:44.000Z
modified: 2018-08-27T19:34:17.000Z
contributor: AAS Frey.Katie
creator: AAS Frey.Katie Admin
type: Concept
narrower: Open source software
narrower: Private software
narrower: Public domain software
narrower: Publicly available software
broader: Astronomy software
narrower: Software available on request

Public domain software
created: 2018-01-26T16:23:18.000Z
modified: 2018-08-27T19:32:25.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie
broader: Software licensing

Publicly available software
created: 2018-01-26T16:24:26.000Z
modified: 2018-08-27T19:33:34.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Software licensing
contributor: AAS Frey.Katie

Software available on request
created: 2018-01-26T16:26:08.000Z
modified: 2018-08-27T19:33:57.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie
broader: Software licensing

Open source software
created: 2018-01-26T16:26:16.000Z
modified: 2018-08-27T19:30:59.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie
broader: Software licensing

Private software
created: 2018-01-26T16:26:45.000Z
modified: 2018-08-27T19:31:57.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Software licensing
contributor: AAS Frey.Katie

Software documentation
created: 2018-01-26T16:28:39.000Z
modified: 2018-08-27T19:24:49.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy software
narrower: Software tutorials
contributor: AAS Frey.Katie

Educational software
created: 2018-01-26T16:28:51.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomy software
related: Astronomy education
contributor: AAS Frey.Katie
modified: 2020-10-19T17:17:34.992Z

Software tutorials
created: 2018-01-26T16:29:01.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Software documentation

Fast solar wind
created: 2018-02-06T18:35:38.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar wind

Slow solar wind
created: 2018-02-06T18:35:43.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar wind

Solar meridional circulation
created: 2018-02-06T18:42:43.000Z
modified: 2018-08-27T21:29:13.000Z
creator: AAS Frey.Katie
type: Concept
contributor: AAS Frey.Katie
broader: Solar interior

Solar granules
created: 2018-02-06T19:55:04.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar photosphere
alternative label: Solar granule
related: Solar granulation
alternative label: Granule
related: Stellar granules
definition: One of the convective cells constituting the solar granulation.
modified: 2020-11-04T15:24:07.564Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-04T15:24:19.869Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T15:24:19.904Z

RRd variable stars
created: 2018-05-10T14:53:00.000Z
modified: 2018-09-13T16:42:09.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: RR Lyrae variable stars
alternative label: Bailey stars
alternative label: RR(B) stars
alternative label: Bailey type d stars
alternative label: RRd stars
broader: Double-mode variable stars
contributor: AAS Frey.Katie Admin

Magellanic irregular galaxies
created: 2018-05-10T15:00:38.000Z
modified: 2018-05-10T15:05:20.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Irregular galaxies
contributor: AAS Frey.Katie Admin
alternative label: Type I irregular galaxies
alternative label: Irregular I galaxies
scope note: Magellanic irregular is a classification of galaxies. Though the SMC is an example of this classification, it does not specifically describe ONLY the Magellanic Clouds.
narrower: Small Magellanic Cloud

Gamma-ray bursters
created: 2018-06-22T20:07:20.000Z
creator: AAS Frey.Katie Admin
type: Concept
related: Gamma-ray bursts
broader: Gamma-ray transient sources
related: Gamma-ray sources
definition: The object or phenomenon at the origin of a gamma-ray burst.
modified: 2020-11-02T16:25:41.564Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:25:55.133Z
modified: 2020-11-02T16:25:55.164Z

Circumgalactic medium
created: 2018-08-17T17:20:31.000Z
modified: 2018-08-17T17:21:03.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy structure
contributor: AAS Frey.Katie
alternative label: Gaseous galaxy halo
broader: Extragalactic astronomy

DC stars
created: 2017-01-23T19:10:45.000Z
creator: AAS Frey.Katie
type: Concept
broader: White dwarf stars
definition: A white dwarf showing a continuous spectrum with no readily apparent lines.
contributor: AAS Frey.Katie Admin
alternative label: DC white dwarf
alternative label: DC white dwarf stars
modified: 2020-11-04T21:15:00.380Z
modified: 2020-11-04T21:14:42.896Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:14:42.863Z
  creator: AAS Frey.Katie Admin

Galaxy dark matter halos
created: 2018-08-17T17:22:25.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy structure
contributor: AAS Frey.Katie
alternative label: Dark matter halos
alternative label: Dark halos
alternative label: Dark halo
related: Milky Way dark matter halo
definition: A vast region surrounding a galaxy where dynamical tracers reveal a large amount of hidden mass. The halo has considerable mass but relatively low luminosity, suggesting the presence of a lot of dark matter.
modified: 2020-11-09T14:57:48.466Z
modified: 2020-11-09T14:57:59.624Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T14:57:59.600Z

Stellar coronal mass ejections
created: 2018-08-17T18:56:19.000Z
modified: 2018-08-17T18:57:05.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar phenomena
contributor: AAS Frey.Katie Admin
related: Solar coronal mass ejections
related: Stellar mass loss
alternative label: Stellar CME
related: Ejecta

Astrostatistics
created: 2018-08-27T18:47:48.000Z
creator: AAS Frey.Katie
type: Concept
broader: Interdisciplinary astronomy
narrower: Algorithms
narrower: Astrostatistics distributions
narrower: Astrostatistics strategies
narrower: Astrostatistics techniques
narrower: Astrostatistics tools
definition: A branch of applied mathematics that deals with the collection and interpretation of quantitative data and the use of probability theory to estimate population parameters, applied to astronomy.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T22:13:54.755Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T22:14:11.679Z
modified: 2020-11-04T22:14:11.707Z

Algorithms
created: 2018-08-27T18:48:52.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics
narrower: Expectation-Maximization Algorithm
narrower: Markov chain Monte Carlo
contributor: AAS Frey.Katie
definition: A step-by-step problem-solving procedure, especially an established, recursive computational procedure for solving a problem in a finite number of steps.
modified: 2020-11-03T17:52:03.688Z
modified: 2020-11-03T17:52:19.230Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T17:52:19.203Z
  creator: AAS Frey.Katie

Astrostatistics distributions
created: 2018-08-27T18:49:13.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics
narrower: Gamma distribution
narrower: Normal distribution
narrower: Pareto distribution
narrower: Poisson distribution
narrower: Sampling distribution

Astrostatistics strategies
created: 2018-08-27T18:49:19.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics
narrower: Bayesian statistics
narrower: Maximum likelihood estimation
narrower: Nonparametric hypothesis tests
narrower: Nonparametric inference
narrower: Parametric hypothesis tests
narrower: Survival analysis

Astrostatistics techniques
created: 2018-08-27T18:49:23.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics
narrower: Bootstrap
narrower: Classification
narrower: Clustering
narrower: Cross-validation
narrower: Deconvolution
narrower: Detection
narrower: Model selection
narrower: Multivariate analysis
narrower: Regression
narrower: Spatial point processes
narrower: Time series analysis
narrower: Uncertainty bounds
narrower: Wavelet analysis

Astrostatistics tools
created: 2018-08-27T18:49:28.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics
narrower: Bayes factor
narrower: Bayesian information criterion
narrower: Chi-squared statistic
narrower: Fisher's Information
narrower: Kullback-Leibler distance

Expectation-Maximization Algorithm
created: 2018-08-27T18:49:46.000Z
creator: AAS Frey.Katie
type: Concept
broader: Algorithms
preferred label: Expectation-Maximisation Algorithm
modified: 2021-09-27T15:46:07.378Z
contributor: AAS Frey.Katie Admin

Markov chain Monte Carlo
created: 2018-08-27T18:49:51.000Z
modified: 2018-08-27T19:32:38.000Z
creator: AAS Frey.Katie
type: Concept
broader: Algorithms
narrower: Affine invariant
narrower: Gibbs Sampler
narrower: Importance sampling
narrower: Metropolis-Hastings
narrower: Nested sampling
contributor: AAS Frey.Katie
broader: Computational methods

Affine invariant
created: 2018-08-27T18:50:03.000Z
creator: AAS Frey.Katie
type: Concept
broader: Markov chain Monte Carlo

Gibbs Sampler
created: 2018-08-27T18:50:07.000Z
creator: AAS Frey.Katie
type: Concept
broader: Markov chain Monte Carlo

Importance sampling
created: 2018-08-27T18:50:11.000Z
creator: AAS Frey.Katie
type: Concept
broader: Markov chain Monte Carlo

Metropolis-Hastings
created: 2018-08-27T18:50:15.000Z
creator: AAS Frey.Katie
type: Concept
broader: Markov chain Monte Carlo

Nested sampling
created: 2018-08-27T18:50:19.000Z
creator: AAS Frey.Katie
type: Concept
broader: Markov chain Monte Carlo

Gamma distribution
created: 2018-08-27T18:50:34.000Z
modified: 2018-08-27T19:04:17.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics distributions
contributor: AAS Frey.Katie
alternative label: Schechter function

Normal distribution
created: 2018-08-27T18:50:38.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics distributions
contributor: AAS Frey.Katie
definition: A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve with a mean at the center of the curve and tail widths proportional to the standard deviation of the data about the mean.
modified: 2020-11-10T19:42:52.195Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:43:01.281Z
modified: 2020-11-10T19:43:01.312Z

Pareto distribution
created: 2018-08-27T18:50:42.000Z
modified: 2018-08-27T19:04:06.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics distributions
contributor: AAS Frey.Katie
alternative label: Power law distribution

Poisson distribution
created: 2018-08-27T18:50:46.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics distributions
contributor: AAS Frey.Katie
definition: A probability function that characterizes discrete random events occurring independently of one another within some definite time or space. It may be regarded as an approximation of the binomial distribution when the number of events becomes large and the probability of success becomes small. The Poisson distribution is expressed by: f(x) = (λxe-λ)/x!, where λ is the mean number of successes in the interval, e is the base of the natural logarithm, and x is the number of successes we are interested in.
modified: 2020-11-17T19:46:15.652Z
modified: 2020-11-17T19:46:25.720Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:46:25.693Z
  creator: AAS Frey.Katie

Sampling distribution
created: 2018-08-27T18:50:50.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics distributions

Bayesian statistics
created: 2018-08-27T18:51:04.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics strategies
narrower: Bayes' Theorem
narrower: Hierarchical models
narrower: Posterior distribution
narrower: Prior distribution

Maximum likelihood estimation
created: 2018-08-27T18:51:08.000Z
modified: 2018-08-27T19:03:29.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics strategies
contributor: AAS Frey.Katie
alternative label: MLE

Nonparametric hypothesis tests
created: 2018-08-27T18:51:12.000Z
modified: 2018-08-27T19:02:59.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics strategies
narrower: Kolmogorov-Smirnov test
contributor: AAS Frey.Katie
related: Nonparametric inference

Nonparametric inference
created: 2018-08-27T18:51:16.000Z
modified: 2018-08-27T19:02:59.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics strategies
narrower: Smoothing
contributor: AAS Frey.Katie
related: Nonparametric hypothesis tests

Parametric hypothesis tests
created: 2018-08-27T18:51:20.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics strategies
narrower: F test

Survival analysis
created: 2018-08-27T18:51:24.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics strategies

Bootstrap
created: 2018-08-27T18:52:03.000Z
modified: 2018-08-27T18:59:37.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
contributor: AAS Frey.Katie
broader: Uncertainty bounds
related: Cross-validation

Classification
created: 2018-08-27T18:52:07.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Mixture model
narrower: Neural networks
narrower: Outlier detection
narrower: Random Forests
narrower: Support vector machine
contributor: AAS Frey.Katie
definition: The systematic grouping of astronomical objects into categories on the basis of physical, morphological, or evolutionary characteristics.
modified: 2020-11-03T19:22:48.447Z
editorial note: Definition Provenance
  created: 2020-11-03T19:23:03.076Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:23:03.102Z

Clustering
created: 2018-08-27T18:52:11.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Single-linkage hierarchical clustering
contributor: AAS Frey.Katie
definition: Grouping of a number of similar astronomical objects.
modified: 2020-11-03T19:26:13.214Z
modified: 2020-11-03T19:26:25.021Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:26:24.989Z
  creator: AAS Frey.Katie

Cross-validation
created: 2018-08-27T18:52:15.000Z
modified: 2018-08-27T18:59:37.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
related: Bootstrap
contributor: AAS Frey.Katie

Deconvolution
created: 2018-08-27T18:52:20.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
contributor: AAS Frey.Katie
definition: A mathematical operation that allows to restore the original input signal, such as an astronomical image or spectrum, to its state before being affected by the atmospheric turbulence and the transfer function of the instrument.
modified: 2020-11-03T20:03:20.134Z
editorial note: Definition Provenance
  created: 2020-11-03T20:03:33.091Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T20:03:33.126Z

Detection
created: 2018-08-27T18:52:24.000Z
contributor: AAS Frey.Katie
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
definition: Any operation on an electrical or electromagnetic signal to recover information from it.
modified: 2020-11-03T20:10:17.760Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:10:27.354Z
  creator: AAS Frey.Katie
modified: 2020-11-03T20:10:27.386Z

Model selection
created: 2018-08-27T18:52:28.000Z
modified: 2018-09-14T15:18:09.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Akaike information criterion
narrower: Likelihood ratio test
contributor: AAS Frey.Katie Admin
narrower: Bayesian information criterion

Multivariate analysis
created: 2018-08-27T18:52:32.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Dimensionality reduction
narrower: Principal component analysis

Regression
created: 2018-08-27T18:52:36.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Linear regression
narrower: Measurement error model
narrower: Minimum chi-squared
narrower: Nonlinear regression
narrower: Robust regression
contributor: AAS Frey.Katie
alternative label: Fitting
related: Smoothing
definition: A method for fitting a curve through a set of points using some goodness-of-fit criterion. The most common type of regression is linear regression.
modified: 2020-11-17T20:19:37.633Z
editorial note: Definition Provenance
  created: 2020-11-17T20:19:48.175Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T20:19:48.203Z

Spatial point processes
created: 2018-08-27T18:52:40.000Z
modified: 2018-08-27T18:57:24.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Minimum spanning tree
contributor: AAS Frey.Katie
narrower: Smoothing
narrower: Two-point correlation function
narrower: Voronoi tessellation

Time series analysis
created: 2018-08-27T18:52:44.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
narrower: Irregular cadence
narrower: Light curve classification
narrower: Period search
narrower: Red noise
narrower: Transient detection
related: Time domain astronomy
modified: 2019-11-25T18:35:01.099Z
contributor: AAS Frey.Katie

Uncertainty bounds
created: 2018-08-27T18:52:49.000Z
modified: 2018-08-27T18:58:47.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
contributor: AAS Frey.Katie
narrower: Bootstrap
narrower: Confidence interval
narrower: Credible region

Wavelet analysis
created: 2018-08-27T18:52:53.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics techniques
modified: 2020-11-04T21:18:15.749Z
definition: A refinement of Fourier analysis which enables to simplify the description of a complicated function in terms of a small number of coefficients. The formal history of wavelet theory began in the early 1980s when Jean Morlet, a French geophysicist, introduced the concept of wavelet and studied wavelet transform as a new tool for scientific signal analysis. In 1984, his collaboration with Alex Grossmann yielded a detailed mathematical study of the continuous wavelet transforms and their various applications. Although similar results had already been obtained 20-50 years earlier by several other researchers, the rediscovery of the old concepts provided a new method for decomposing functions.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:18:29.642Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:18:29.617Z
  creator: AAS Frey.Katie Admin

Bayes factor
created: 2018-08-27T18:53:13.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics tools

Bayesian information criterion
created: 2018-08-27T18:53:17.000Z
modified: 2018-09-14T15:17:59.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics tools
contributor: AAS Frey.Katie Admin
broader: Model selection

Chi-squared statistic
created: 2018-08-27T18:53:21.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics tools

Fisher's Information
created: 2018-08-27T18:53:25.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics tools

Kullback-Leibler distance
created: 2018-08-27T18:53:28.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrostatistics tools

Bayes' Theorem
created: 2018-08-27T18:53:54.000Z
creator: AAS Frey.Katie
type: Concept
broader: Bayesian statistics
contributor: AAS Frey.Katie
definition: A theorem in probability theory concerned with determining the conditional probability of an event when another event has occurred. Bayes' theorem allows revision of the original probability with new information. Its simplest form is: P(A|B) = P(B|A) P(A)/P(B), where P(A): independent probability of A, also called prior probability; P(B): independent probability of B; P(B|A): conditional probability of B given A has occurred; P(A|B): conditional probability of A given B has occurred, also called posterior probability. Same as Bayes' rule.
modified: 2020-11-03T18:45:38.746Z
modified: 2020-11-03T18:45:57.405Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:45:57.379Z

Hierarchical models
created: 2018-08-27T18:53:58.000Z
creator: AAS Frey.Katie
type: Concept
broader: Bayesian statistics

Posterior distribution
created: 2018-08-27T18:54:02.000Z
creator: AAS Frey.Katie
type: Concept
broader: Bayesian statistics

Prior distribution
created: 2018-08-27T18:54:06.000Z
creator: AAS Frey.Katie
type: Concept
broader: Bayesian statistics

Kolmogorov-Smirnov test
created: 2018-08-27T18:54:23.000Z
creator: AAS Frey.Katie
type: Concept
broader: Nonparametric hypothesis tests

Smoothing
created: 2018-08-27T18:54:36.000Z
creator: AAS Frey.Katie
type: Concept
broader: Nonparametric inference
narrower: Gaussian Processes regression
contributor: AAS Frey.Katie
related: Regression
broader: Spatial point processes
definition: The mathematical process that makes a curve smooth.
modified: 2020-11-19T15:29:17.227Z
modified: 2020-11-19T15:29:27.760Z
editorial note: Definition Provenance
  created: 2020-11-19T15:29:27.731Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Gaussian Processes regression
created: 2018-08-27T18:54:43.000Z
creator: AAS Frey.Katie
type: Concept
broader: Smoothing

F test
created: 2018-08-27T18:54:53.000Z
creator: AAS Frey.Katie
type: Concept
broader: Parametric hypothesis tests

Mixture model
created: 2018-08-27T18:55:05.000Z
creator: AAS Frey.Katie
type: Concept
broader: Classification
narrower: Gaussian mixture model

Neural networks
created: 2018-08-27T18:55:09.000Z
creator: AAS Frey.Katie
type: Concept
broader: Classification
narrower: Convolutional neural networks

Outlier detection
created: 2018-08-27T18:55:14.000Z
creator: AAS Frey.Katie
type: Concept
broader: Classification

Random Forests
created: 2018-08-27T18:55:18.000Z
creator: AAS Frey.Katie
type: Concept
broader: Classification

Support vector machine
created: 2018-08-27T18:55:22.000Z
creator: AAS Frey.Katie
type: Concept
broader: Classification

Gaussian mixture model
created: 2018-08-27T18:55:32.000Z
creator: AAS Frey.Katie
type: Concept
broader: Mixture model

Convolutional neural networks
created: 2018-08-27T18:55:39.000Z
modified: 2018-08-27T19:02:41.000Z
creator: AAS Frey.Katie
type: Concept
broader: Neural networks
contributor: AAS Frey.Katie
alternative label: Deep learning

Single-linkage hierarchical clustering
created: 2018-08-27T18:55:49.000Z
modified: 2018-08-27T19:01:31.000Z
creator: AAS Frey.Katie
type: Concept
broader: Clustering
contributor: AAS Frey.Katie
alternative label: friend-of-friends algorithm
related: Minimum spanning tree
alternative label: friend-of-a-friend algorithm

Akaike information criterion
created: 2018-08-27T18:55:59.000Z
creator: AAS Frey.Katie
type: Concept
broader: Model selection

Likelihood ratio test
created: 2018-08-27T18:56:07.000Z
creator: AAS Frey.Katie
type: Concept
broader: Model selection

Dimensionality reduction
created: 2018-08-27T18:56:18.000Z
creator: AAS Frey.Katie
type: Concept
broader: Multivariate analysis

Principal component analysis
created: 2018-08-27T18:56:27.000Z
creator: AAS Frey.Katie
type: Concept
broader: Multivariate analysis

Linear regression
created: 2018-08-27T18:56:37.000Z
creator: AAS Frey.Katie
type: Concept
broader: Regression
contributor: AAS Frey.Katie
modified: 2020-11-10T18:31:27.394Z
definition: In statistics, a regression method that establishes a linear relationship between two random variables.
editorial note: Definition provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-20T19:23:43.378Z
modified: 2020-11-10T18:31:49.520Z

Measurement error model
created: 2018-08-27T18:56:40.000Z
creator: AAS Frey.Katie
type: Concept
broader: Regression

Minimum chi-squared
created: 2018-08-27T18:56:44.000Z
creator: AAS Frey.Katie
type: Concept
broader: Regression

Nonlinear regression
created: 2018-08-27T18:56:48.000Z
creator: AAS Frey.Katie
type: Concept
broader: Regression

Robust regression
created: 2018-08-27T18:56:56.000Z
creator: AAS Frey.Katie
type: Concept
broader: Regression

Minimum spanning tree
created: 2018-08-27T18:57:15.000Z
modified: 2018-08-27T19:00:23.000Z
creator: AAS Frey.Katie
type: Concept
broader: Spatial point processes
contributor: AAS Frey.Katie
related: Single-linkage hierarchical clustering

Two-point correlation function
created: 2018-08-27T18:57:32.000Z
creator: AAS Frey.Katie
type: Concept
broader: Spatial point processes

Voronoi tessellation
created: 2018-08-27T18:57:36.000Z
creator: AAS Frey.Katie
type: Concept
broader: Spatial point processes

Irregular cadence
created: 2018-08-27T18:57:54.000Z
creator: AAS Frey.Katie
type: Concept
broader: Time series analysis

Light curve classification
created: 2018-08-27T18:57:58.000Z
modified: 2018-09-07T21:50:39.000Z
creator: AAS Frey.Katie
type: Concept
broader: Time series analysis
contributor: AAS Frey.Katie
related: Light curves

Period search
created: 2018-08-27T18:58:02.000Z
creator: AAS Frey.Katie
type: Concept
broader: Time series analysis
narrower: Fast Fourier transform
narrower: Lomb-Scargle periodogram
narrower: Phase dispersion minimization

Red noise
created: 2018-08-27T18:58:06.000Z
creator: AAS Frey.Katie
type: Concept
broader: Time series analysis

Transient detection
created: 2018-08-27T18:58:10.000Z
creator: AAS Frey.Katie
type: Concept
broader: Time series analysis

Fast Fourier transform
created: 2018-08-27T18:58:25.000Z
creator: AAS Frey.Katie
type: Concept
broader: Period search

Lomb-Scargle periodogram
created: 2018-08-27T18:58:29.000Z
creator: AAS Frey.Katie
type: Concept
broader: Period search
contributor: AAS Frey.Katie
definition: An algorithm for detecting and characterizing periodic signals in unevenly-sampled data. The Lomb-Scargle periodogram has a particularly wide use within the astronomy community. This method allows efficient computation of a Fourier-like power spectrum estimator from such unevenly-sampled data, resulting in an intuitive means of determining the period of oscillation.
modified: 2020-11-10T18:33:54.444Z
modified: 2020-11-10T18:34:04.083Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:34:04.057Z
  creator: AAS Frey.Katie

Phase dispersion minimization
created: 2018-08-27T18:58:33.000Z
creator: AAS Frey.Katie
type: Concept
broader: Period search
preferred label: Phase dispersion minimisation
modified: 2021-09-27T15:46:22.648Z
contributor: AAS Frey.Katie Admin

Confidence interval
created: 2018-08-27T18:58:58.000Z
creator: AAS Frey.Katie
type: Concept
broader: Uncertainty bounds

Credible region
created: 2018-08-27T18:59:03.000Z
creator: AAS Frey.Katie
type: Concept
broader: Uncertainty bounds

Hydrodynamics
created: 2018-08-27T19:17:51.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrophysical fluid dynamics
contributor: AAS Frey.Katie
related: Hydrodynamical simulations
definition: The branch of physics dealing with the motion, energy, and pressure of neutral fluids.
modified: 2020-11-09T16:51:24.700Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-09T16:51:34.667Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T16:51:34.696Z

Magnetohydrodynamics
created: 2018-08-27T19:18:18.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrophysical fluid dynamics
alternative label: MHD
related: Magnetohydrodynamical simulations
broader: Plasma astrophysics
contributor: AAS Frey.Katie
related: Alfven waves
definition: The dynamics of an ionized plasma in the non-relativistic, collisional case. In this description, charge oscillations and high frequency electromagnetic waves are neglected. It is an important field of astrophysics since plasma is one of the commonest forms of matter in the Universe, occurring in stars, planetary magnetospheres, and interplanetary and interstellar space.
modified: 2020-11-10T19:07:35.748Z
modified: 2020-11-10T19:07:45.511Z
editorial note: Definition Provenance
  created: 2020-11-10T19:07:45.483Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Computational methods
created: 2018-08-27T19:21:45.000Z
modified: 2018-08-27T19:32:38.000Z
creator: AAS Frey.Katie
type: Concept
broader: Computational astronomy
contributor: AAS Frey.Katie
narrower: Markov chain Monte Carlo
narrower: Astronomy databases
narrower: GPU computing
narrower: Cloud computing
narrower: Distributed computing

Magnetohydrodynamical simulations
created: 2018-08-27T19:23:52.000Z
modified: 2018-08-27T19:39:45.000Z
related: Magnetohydrodynamics
creator: AAS Frey.Katie
type: Concept
broader: Astronomical simulations
contributor: AAS Frey.Katie

Radiative transfer simulations
created: 2018-08-27T19:24:32.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astronomical simulations

Astronomy data visualization
created: 2018-08-27T19:36:17.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astronomy data analysis
preferred label: Astronomy data visualisation
modified: 2021-09-27T15:40:00.708Z
contributor: AAS Frey.Katie Admin

GPU computing
created: 2018-08-27T19:38:21.000Z
creator: AAS Frey.Katie
type: Concept
broader: Computational methods

Cloud computing
created: 2018-08-27T19:38:32.000Z
creator: AAS Frey.Katie
type: Concept
broader: Computational methods

Distributed computing
created: 2018-08-27T19:38:47.000Z
creator: AAS Frey.Katie
type: Concept
broader: Computational methods

Center to limb observations
created: 2018-08-27T19:40:50.000Z
creator: AAS Frey.Katie
type: Concept
broader: Optical observation
contributor: AAS Frey.Katie Admin
preferred label: Centre to limb observations
modified: 2021-08-24T15:25:23.835Z

Spectropolarimetry
created: 2018-08-27T19:41:07.000Z
creator: AAS Frey.Katie
type: Concept
broader: Polarimetry
contributor: AAS Frey.Katie
alternative label: Spectro-polarimetry
related: Solar electromagnetic emission
definition: A technique of observation in astrophysics which combines spectroscopy and polarization measurements. Spectropolarimetry has a wide range of applications in astrophysics, including stellar magnetic field studies.
modified: 2020-11-19T16:08:05.592Z
modified: 2020-11-19T16:08:15.206Z
editorial note: Definition Provenance
  created: 2020-11-19T16:08:15.180Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Solar active regions
created: 2018-08-27T19:48:37.000Z
modified: 2018-08-29T15:42:41.000Z
alternative label: Active solar regions
creator: AAS Frey.Katie
type: Concept
broader: Solar activity
contributor: AAS Frey.Katie
narrower: Sunspots
narrower: Ephemeral active regions
narrower: Solar active region magnetic fields
narrower: Solar active region velocity fields
narrower: Solar active region filaments

Solar active region magnetic fields
created: 2018-08-27T19:49:07.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar active regions

Solar active region velocity fields
created: 2018-08-27T19:49:11.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar active regions

Solar active region filaments
created: 2018-08-27T19:49:16.000Z
modified: 2018-08-27T21:01:11.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar active regions
broader: Solar filaments
contributor: AAS Frey.Katie

Sunspot flow
created: 2018-08-27T19:50:02.000Z
creator: AAS Frey.Katie
type: Concept
broader: Sunspots

Delta sunspots
created: 2018-08-27T19:50:20.000Z
creator: AAS Frey.Katie
type: Concept
broader: Sunspots

Active solar chromosphere
created: 2018-08-27T21:01:35.000Z
modified: 2018-08-27T21:04:46.000Z
broader: Solar chromosphere
creator: AAS Frey.Katie
type: Concept
contributor: AAS Frey.Katie

Solar filament eruptions
created: 2018-08-27T21:01:47.000Z
modified: 2018-09-17T20:25:28.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar filaments
contributor: AAS Frey.Katie Admin

Solar flare spectra
created: 2018-08-27T21:02:43.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar flares

Solar white-light flares
created: 2018-08-27T21:02:51.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar flares

Solar magnetic bright points
created: 2018-08-27T21:03:12.000Z
modified: 2018-08-27T21:34:22.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar activity
contributor: AAS Frey.Katie
broader: Solar magnetic fields

Ellerman Bombs
created: 2018-08-27T21:05:59.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar chromosphere

Quiet solar chromosphere
created: 2018-08-27T21:06:17.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar chromosphere

Solar chromospheric heating
created: 2018-08-27T21:06:41.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar chromosphere

Active solar corona
created: 2018-08-27T21:08:39.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona

Solar coronal heating
created: 2018-08-27T21:09:22.000Z
modified: 2018-08-29T14:48:56.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona
contributor: AAS Frey.Katie

Solar E corona
created: 2018-08-27T21:11:00.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona
modified: 2020-11-04T15:09:55.802Z
alternative label: E region
alternative label: E corona
related: Stellar E corona
alternative label: Solar E coronal region
definition: A part of the solar corona defined by the emission lines of hot gases. These emission lines include the so-called forbidden lines of the strongly ionized atoms of iron, calcium, and other elements. The E corona is thinner than the K corona and the F corona.
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T15:10:10.381Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T15:10:10.427Z

Solar F corona
created: 2018-08-27T21:11:57.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona
alternative label: F region
related: Stellar F corona
alternative label: Solar F coronal region
alternative label: F corona
definition: The exterior part of the solar corona, illuminated by solar light scattered or reflected by dust particles. The same phenomenon also produces the zodiacal light, much farther away from the Sun. The dust particles are at most several microns in size and make up a disk stretching over almost 1 solar radius (700,000 km) from the Sun's surface. Unlike electrons, which are responsible for the K corona, the dust particles move relatively slowly. Thus, the light scattered by them has the same spectrum as the photosphere and shows the Fraunhofer lines. The F corona is the most luminous part of the corona at 1.5 solar radii from the Sun's surface.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:10:50.435Z
modified: 2020-11-04T15:11:09.607Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T15:11:09.575Z
  creator: AAS Frey.Katie Admin

Quiet solar corona
created: 2018-08-27T21:12:53.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona

Solar coronal radio emission
created: 2018-08-27T21:13:15.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona

Solar coronal seismology
created: 2018-08-27T21:13:19.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona

Solar coronal waves
created: 2018-08-27T21:13:23.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona

Solar differential rotation
created: 2018-08-27T21:21:00.000Z
modified: 2018-08-27T21:28:23.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar rotation
broader: Solar interior
contributor: AAS Frey.Katie

Solar coronal mass ejection shocks
created: 2018-08-27T21:21:39.000Z
modified: 2018-09-20T16:50:38.000Z
creator: AAS Frey.Katie
type: Concept
broader: Shocks
alternative label: Solar CME shocks
broader: Solar particle emission
contributor: AAS Frey.Katie Admin

Solar convective zone
created: 2018-08-27T21:29:40.000Z
modified: 2018-09-13T21:53:48.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar interior
contributor: AAS Frey.Katie
related: Stellar convective zones

Solar radiative zone
created: 2018-08-27T21:29:45.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar interior

Solar magnetic flux emergence
created: 2018-08-27T21:34:10.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar magnetic fields

Solar dynamo
created: 2018-08-27T21:34:33.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar magnetic fields
contributor: AAS Frey.Katie
broader: Solar cycle
definition: A model for explaining the generation of the solar magnetic field and the related observational features (mainly solar cycle, Sporer's law, Hale's law, Joy's law, polarity reversal). The global frame of this model is the interaction between a turbulent plasma in the convective zone (reciprocal generation of magnetic and electric fields) and the solar differential rotation (mutual transformation of meridional magnetic field into azimuthal magnetic field).
modified: 2020-11-19T15:46:43.590Z
modified: 2020-11-19T15:46:53.908Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T15:46:53.876Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Galactic abundances
created: 2018-08-27T21:46:03.000Z
modified: 2018-08-27T21:47:07.000Z
creator: AAS Frey.Katie
type: Concept
broader: Chemical abundances
contributor: AAS Frey.Katie
related: Galaxy abundances
broader: Milky Way Galaxy physics

Intergalactic abundances
created: 2018-08-27T21:46:33.000Z
creator: AAS Frey.Katie
type: Concept
broader: Chemical abundances

Laboratory astrophysics
created: 2018-08-27T21:48:10.000Z
creator: AAS Frey.Katie
type: Concept
broader: Interdisciplinary astronomy
contributor: AAS Frey.Katie Admin
narrower: Molecular physics
narrower: Atomic physics
narrower: Nuclear physics
narrower: Particle physics
narrower: Plasma physics
narrower: Solid matter physics
narrower: Theoretical techniques
narrower: Experimental techniques
related: Spectral line lists
narrower: Theoretical models
modified: 2022-06-11T21:51:23.086Z
narrower: Experimental data
narrower: Theoretical data

Rich galaxy clusters
created: 2018-08-29T14:45:08.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy clusters
alternative label: Rich clusters
definition: A galaxy cluster with a particularly large number of galaxies.
modified: 2020-11-03T21:32:25.987Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:32:40.883Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T21:32:40.913Z

Poor galaxy clusters
created: 2018-08-29T14:45:15.000Z
modified: 2018-08-29T14:46:37.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy clusters
contributor: AAS Frey.Katie
alternative label: Poor clusters

High-redshift galaxy clusters
created: 2018-08-29T14:45:20.000Z
modified: 2018-08-29T14:46:26.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy clusters
contributor: AAS Frey.Katie
alternative label: High redshift clusters
alternative label: High-redshift clusters

Radio transient sources
created: 2018-08-29T18:36:06.000Z
modified: 2018-08-29T19:34:31.000Z
creator: AAS Frey.Katie
type: Concept
broader: Transient sources
contributor: AAS Frey.Katie
alternative label: Fast radio burst
alternative label: Fast radio bursts
alternative label: Lorimer Burst
alternative label: FRB
alternative label: FRBs
broader: Radio sources
related: Radio bursts

Radiative magnetohydrodynamics
created: 2018-08-29T20:18:16.000Z
modified: 2018-08-29T20:18:26.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrophysical fluid dynamics
contributor: AAS Frey.Katie
alternative label: Radiative MHD

SRa variable stars
created: 2018-08-30T19:56:55.000Z
modified: 2018-08-30T19:57:55.000Z
creator: AAS Frey.Katie
type: Concept
broader: Semi-regular variable stars
contributor: AAS Frey.Katie
alternative label: SRA stars
alternative label: SRa stars

SRb variable stars
created: 2018-08-30T19:57:05.000Z
modified: 2018-08-30T19:59:19.000Z
creator: AAS Frey.Katie
type: Concept
broader: Semi-regular variable stars
contributor: AAS Frey.Katie
alternative label: SRb stars
alternative label: SRB stars

SRc variable stars
created: 2018-08-30T19:57:16.000Z
creator: AAS Frey.Katie
type: Concept
broader: Semi-regular variable stars

SRd variable stars
created: 2018-08-30T19:57:22.000Z
modified: 2018-09-13T16:48:02.000Z
creator: AAS Frey.Katie
type: Concept
broader: Semi-regular variable stars
contributor: AAS Frey.Katie Admin
narrower: UU Herculis stars

SRS variable stars
created: 2018-08-30T19:57:30.000Z
creator: AAS Frey.Katie
type: Concept
broader: Semi-regular variable stars

FK Comae stars
created: 2018-08-30T20:01:22.000Z
modified: 2018-08-30T20:02:57.000Z
creator: AAS Frey.Katie
type: Concept
contributor: AAS Frey.Katie
broader: Ellipsoidal variable stars

Quenched galaxies
created: 2018-08-30T20:04:20.000Z
modified: 2018-09-07T19:38:33.000Z
creator: AAS Frey.Katie
type: Concept
contributor: AAS Frey.Katie
broader: Galaxies
related: Galaxy quenching

AGN host galaxies
created: 2018-08-30T20:58:58.000Z
modified: 2018-08-30T20:59:06.000Z
related: Active galactic nuclei
creator: AAS Frey.Katie
type: Concept
broader: Active galaxies
contributor: AAS Frey.Katie

Biosignatures
created: 2018-08-30T21:03:17.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astrobiology
contributor: AAS Frey.Katie
alternative label: Biomarkers
modified: 2019-12-03T18:57:04.641Z

Reverberation mapping
created: 2018-08-30T21:04:57.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astronomical techniques

Exoplanet atmospheric variability
created: 2018-08-30T21:20:24.000Z
creator: AAS Frey.Katie
type: Concept
broader: Exoplanet atmospheres
related: Atmospheric variability
alternative label: Exoplanet atmosphere variability
modified: 2022-06-21T17:39:43.310Z
contributor: AAS Frey.Katie Admin

Exoplanet atmospheric composition
created: 2018-08-30T21:20:36.000Z
creator: AAS Frey.Katie
type: Concept
broader: Exoplanet atmospheres
related: Atmospheric composition
alternative label: Exoplanet atmosphere composition
modified: 2022-06-21T17:39:28.976Z
contributor: AAS Frey.Katie Admin

Exoplanet surface composition
created: 2018-08-30T21:21:28.000Z
creator: AAS Frey.Katie
type: Concept
broader: Exoplanet surface characteristics
related: Surface composition
modified: 2022-06-21T17:43:49.554Z
contributor: AAS Frey.Katie Admin

Exoplanet surface variability
created: 2018-08-30T21:21:32.000Z
creator: AAS Frey.Katie
type: Concept
broader: Exoplanet surface characteristics
related: Surface variability
modified: 2022-06-21T17:44:01.168Z
contributor: AAS Frey.Katie Admin

Extrasolar ice giants
created: 2018-08-30T21:22:33.000Z
creator: AAS Frey.Katie
type: Concept
broader: Exoplanets

Irregular natural satellites (Extrasolar)
created: 2018-08-30T21:30:04.000Z
creator: AAS Frey.Katie
type: Concept
broader: Natural satellites (Extrasolar)
contributor: AAS Frey.Katie Admin
alternative label: Irregular exomoons
alternative label: Irregular extrasolar natural satellites
alternative label: Irregular natural extrasolar satellites
alternative label: Irregular moons (Extrasolar)
related: Irregular satellites
definition: A satellite whose orbit around its exoplanet is eccentric, inclined with respect to the equatorial plane, and relatively far from the planet. Strong stellar perturbations cause the orbit to precess.
modified: 2020-11-03T16:19:19.555Z
editorial note: Definition Provenance
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:19:38.566Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:19:38.605Z

M-sigma relation
created: 2018-08-30T21:37:14.000Z
creator: AAS Frey.Katie
type: Concept
broader: Black hole physics

Irregular satellites
created: 2018-08-30T21:38:16.000Z
creator: AAS Frey.Katie
type: Concept
broader: Natural satellites (Solar system)
alternative label: Irregular moons (Solar system)
alternative label: Irregular natural satellites
related: Irregular natural satellites (Extrasolar)
definition: A satellite whose orbit around its planet is eccentric, inclined with respect to the equatorial plane, and relatively far from the planet. Strong solar perturbations cause the orbit to precess.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:18:27.654Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:18:44.864Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:18:44.891Z

Galaxy environments
created: 2018-08-31T19:57:37.000Z
creator: AAS Frey.Katie
type: Concept
broader: Extragalactic astronomy

Photometer
created: 2018-09-04T21:20:03.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astronomical instrumentation
contributor: AAS Frey.Katie
definition: An instrument for measuring the amount of light.
modified: 2020-11-17T19:30:52.211Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:31:01.618Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:31:01.647Z

Cooling flows
created: 2018-09-06T14:23:02.000Z
creator: AAS Frey.Katie
type: Concept
broader: Cool intergalactic medium
contributor: AAS Frey.Katie
broader: Intracluster medium
definition: A phenomenon observed in a cluster of galaxies, whereby the cluster core loses energy via X-ray radiation because of the collisions between the gas particles. The radiation rate is proportional to the square of the density, and the cooling time, which remains in the outer parts too large, becomes smaller than the Hubble time in the core. As a result, the central regions of clusters of galaxies cool down; and since in the center of a cluster gas pressure and gravitational attraction are in equilibrium, the gas density has to rise to maintain the pressure necessary for supporting the outer layers of gas. To cause its density to rise, the cooled gas has to flow inward. As the densest gas, which cools quickest, is already concentrated in the center of the cluster, the inward flow will start at the center, soon followed by the outer layers. This flow of gas is called the cooling flow. Cooling flows are moderated through feedback due to the supermassive black hole in the nucleus of the central galaxy. The gas inflow to the center fuels the active galactic nucleus (AGN). The latter then heats again the gas through its radio jets.
modified: 2020-10-27T13:22:16.889Z
modified: 2020-10-27T13:22:28.251Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-27T13:22:28.222Z
  creator: AAS Frey.Katie

Scaling relations
created: 2018-09-06T14:29:48.000Z
modified: 2018-09-06T14:44:22.000Z
broader: Astronomical techniques
creator: AAS Frey.Katie
type: Concept
broader: Galaxy properties
contributor: AAS Frey.Katie

Galaxy spheroids
created: 2018-09-06T14:30:49.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy structure

Low-luminosity active galactic nuclei
created: 2018-09-06T14:41:55.000Z
modified: 2018-09-06T14:42:03.000Z
creator: AAS Frey.Katie
type: Concept
broader: Active galactic nuclei
contributor: AAS Frey.Katie
alternative label: Low-luminosity AGN

High-luminosity active galactic nuclei
created: 2018-09-06T14:42:23.000Z
modified: 2018-09-06T14:42:30.000Z
creator: AAS Frey.Katie
type: Concept
broader: Active galactic nuclei
contributor: AAS Frey.Katie
alternative label: High-luminosity AGN

X-ray active galactic nuclei
created: 2018-09-06T14:42:59.000Z
creator: AAS Frey.Katie
type: Concept
broader: Active galactic nuclei
contributor: AAS Frey.Katie
alternative label: X-ray AGN
alternative label: X-ray AGNs
modified: 2019-12-11T20:19:36.711Z

Main belt asteroids
created: 2018-09-06T14:45:31.000Z
creator: AAS Frey.Katie
type: Concept
broader: Asteroids
contributor: AAS Frey.Katie Admin
definition: Asteroids in our solar system that are found in the area between Mars and Jupiter.
related: Asteroid belt
narrower: Vesta
narrower: Ceres
modified: 2022-06-21T18:30:40.244Z
narrower: Pallas
editorial note: Definition Provenance
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:32:05.938Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T18:32:05.963Z

Space weather
created: 2018-09-06T14:45:49.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar system
definition: The varying conditions in space and specifically in the near-Earth environment. Space weather is chiefly solar driven, resulting from solar activities such as solar flares, solar wind, and coronal mass ejections that affect magnetosphere, ionosphere, and thermosphere. Non-solar sources such as Galactic cosmic rays, meteoroids, and space debris can all be considered as altering space weather conditions at the Earth. Space weather may affect the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health. The research in this field aims at monitoring and diagnosis of space weather conditions and constructing reliable numerical prediction models.
related: Solar-planetary interactions
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T15:09:19.406Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-19T16:04:51.429Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:04:51.468Z

Solar coronal lines
created: 2018-09-07T17:36:26.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona
related: Stellar coronal lines
definition: An emission line in the spectrum of the solar corona caused by highly ionized metal ions; especially those of iron, such as the red and green lines at 6375 Å and 5303 Å [Fe X] and [Fe XIV], respectively. From their discovery in 1870 until 1939, it was believed that these forbidden lines would be due to an unknown element, called coronium. Ultraviolet and X-ray coronal lines are also detectable in stars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:05:33.159Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:05:49.798Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T15:05:49.825Z

Solar coronal plumes
created: 2018-09-07T17:38:47.000Z
creator: AAS Frey.Katie
type: Concept
broader: Solar corona
related: Stellar coronal plumes
alternative label: Polar plume
contributor: AAS Frey.Katie Admin
alternative label: Solar polar plume
definition: A coronal feature of the Sun, which appears as long, thin streamers that project outward from the Sun's north and south poles.
modified: 2020-11-04T15:17:05.842Z
modified: 2020-11-04T15:17:17.131Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:17:17.097Z

Galaxy quenching
created: 2018-09-07T19:38:05.000Z
modified: 2018-09-07T19:38:33.000Z
creator: AAS Frey.Katie
type: Concept
broader: Galaxy evolution
contributor: AAS Frey.Katie
related: Quenched galaxies

Galactic bulge
created: 2018-09-07T20:20:17.000Z
creator: AAS Frey.Katie
type: Concept
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
alternative label: Milky Way bulge
related: Galaxy bulges
scope note: Referring to the bulge in the Milky Way Galaxy. For other galaxies use "Galaxy bulges."
modified: 2020-11-09T14:50:20.301Z
definition: The central galaxy bulge of the Milky Way.
modified: 2020-11-09T14:50:35.674Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T14:50:35.645Z
  creator: AAS Frey.Katie

Cosmic background radiation
created: 2018-09-07T20:29:37.000Z
modified: 2018-09-07T20:37:03.000Z
creator: AAS Frey.Katie
type: Concept
contributor: AAS Frey.Katie
broader: Recombination (cosmology)
alternative label: CBR
narrower: Cosmic microwave background radiation
scope note: Use for cosmic background radiations other than microwave, i.e. Cosmic gamma-ray background radiation or Cosmic ultraviolet background radiation, etc.

Solar K corona
created: 2018-09-07T21:44:38.000Z
related: Stellar K corona
creator: AAS Frey.Katie
type: Concept
broader: Solar corona
alternative label: K region
alternative label: Solar K coronal region
alternative label: K corona
definition: The inner part of the solar corona which extends to about two solar radii. It is due to the Thomson scattering of light from the photosphere by the free electrons in the corona. The K corona exhibits a linearly polarized continuous spectrum. The high speeds of the scattering electrons (on the average 10,000 km s^-1 for a temperature of 2 million K) smear out the Fraunhofer lines except the H and K lines.
modified: 2020-11-04T15:12:02.383Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:12:18.251Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T15:12:18.221Z
  creator: AAS Frey.Katie Admin

Morgan-Keenan classification
created: 2018-09-07T22:18:43.000Z
related: Stellar spectral types
creator: AAS Frey.Katie
type: Concept
broader: Stellar classification
alternative label: MK classification
alternative label: MKK classification
alternative label: Yerkes classification
alternative label: Yerkes spectral classification
alternative label: Morgan-Keenan-Kellman classification
modified: 2020-12-16T20:43:25.031Z
contributor: AAS Frey.Katie Admin

Schonberg-Chandrasekhar limit
created: 2018-09-10T16:07:43.000Z
alternative label: Chandrasekhar-Schonberg limit
related: Stellar evolution
creator: AAS Frey.Katie
type: Concept
broader: Gravitational collapse
scope note: Not to be confused with the Chandrasekhar limit.
alternative label: Schoenberg-Chandrasekhar limit
alternative label: Schönberg-Chandrasekhar limit
definition: During the main sequence stage, a star burns the hydrogen in its core and transforms it into helium. When the helium mass amounts to about 10% of the initial stellar mass, the star can no longer maintain the hydrostatic equilibrium in its core; the star increases its volume and leaves the main sequence in order to become a red giant.
contributor: AAS Frey.Katie Admin
modified: 2021-03-30T14:11:50.521Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:36:29.431Z
modified: 2020-11-17T20:36:29.462Z
contributor: AAS Frey.Katie

Stellar evolutionary models
created: 2018-09-13T14:51:48.000Z
modified: 2018-09-13T14:55:58.000Z
creator: AAS Frey.Katie
type: Concept
broader: Astronomical research
contributor: AAS Frey.Katie
narrower: Stellar evolutionary tracks
related: Stellar evolution
narrower: Hertzsprung Russell diagram

Main sequence
created: 2018-09-13T14:54:24.000Z
related: Main sequence stars
creator: AAS Frey.Katie
type: Concept
broader: Hertzsprung Russell diagram
related: Zero-age main sequence stars
related: Dwarf stars
contributor: AAS Frey.Katie
definition: An evolutionary stage in the life of a star when it generates its energy by the conversion of hydrogen to helium via nuclear fusion in its core. Stars spend 90% of their life on the main sequence. On the Hertzsprung-Russell diagram it appears as a track running from top left (high temperature, high luminosity, high mass) to lower right (low temperature, low luminosity, low mass).
modified: 2020-11-10T19:11:26.949Z
modified: 2020-11-10T19:11:39.238Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T19:11:39.197Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Horizontal branch
created: 2018-09-13T14:55:08.000Z
creator: AAS Frey.Katie
type: Concept
broader: Hertzsprung Russell diagram
contributor: AAS Frey.Katie Admin
related: Horizontal branch stars
related: Zero-age horizontal branch stars
related: Extreme horizontal branch stars
definition: A set of roughly horizontal points in the Hertzsprung-Russell diagram of a typical globular cluster. It displays a stage of stellar evolution which immediately follows the red giant branch (RGB) in stars with an initial mass < 1.2 M_sun. When the star's ascent of the RGB is terminated by the helium flash, it moves down to the Horizontal Branch (HB). The star's effective temperature on the HB is higher than it was on the RGB, but the luminosity is considerably less than at the helium flash. Usually HB stars have two energy sources: in addition to the helium burning in their cores, they experience hydrogen fusion in a surrounding shell. The thickness of the shell determines the color of the HB stars. A thin shell, involving low opacity, makes the star look blue. The HB domain encompasses a very large effective temperature range with several members: extreme HB, blue HB, RR Lyrae, red HB, and red clump stars. The locations depend on many parameters, including stellar mass, metallicity, age, helium abundance, and rotation.
modified: 2020-11-02T16:46:03.527Z
editorial note: Definition Provenance
  created: 2020-11-02T16:46:23.192Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-02T16:46:23.219Z

Young massive clusters
created: 2018-09-13T14:58:00.000Z
creator: AAS Frey.Katie
type: Concept
broader: Star clusters

Low mass stars
created: 2018-09-13T15:44:49.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar types
alternative label: Low-mass star
contributor: AAS Frey.Katie Admin
definition: A star whose mass is around that of the Sun.
modified: 2020-11-03T16:45:34.843Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:45:49.645Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:45:49.673Z

Stellar evolutionary types
created: 2018-09-13T16:55:49.000Z
modified: 2018-09-13T21:08:56.000Z
narrower: Blue straggler stars
narrower: Brown dwarfs
narrower: Yellow straggler stars
narrower: Main sequence stars
narrower: White dwarf stars
narrower: Pre-main sequence stars
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar types
contributor: AAS Frey.Katie Admin
narrower: Horizontal branch stars
narrower: Evolved stars
narrower: Dwarf stars
narrower: Subdwarf stars
narrower: Asymptotic giant branch stars
related: Hertzsprung Russell diagram
narrower: Post-asymptotic giant branch stars

Dwarf stars
created: 2018-09-13T17:00:09.000Z
narrower: O dwarf stars
narrower: B dwarf stars
narrower: T dwarfs
related: Main sequence
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar evolutionary types
narrower: A dwarf stars
narrower: F dwarf stars
narrower: G dwarf stars
narrower: M dwarf stars
related: Main sequence stars
narrower: K dwarf stars
contributor: AAS Frey.Katie
definition: A star that burns its hydrogen content to produce its energy and therefore belongs to the main-sequence luminosity class.
modified: 2020-10-26T18:18:52.714Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:19:26.844Z
  creator: AAS Frey.Katie
modified: 2020-10-26T18:19:26.880Z

Subdwarf stars
created: 2018-09-13T17:00:21.000Z
narrower: T subdwarfs
narrower: B subdwarf stars
narrower: O subdwarf stars
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar evolutionary types
contributor: AAS Frey.Katie Admin
narrower: A subdwarf stars
narrower: F subdwarf stars
narrower: G subdwarf stars
definition: A metal-poor main-sequence star with spectral type later than M7 and luminosity class VI. They are population II dwarfs which appear less luminous than their solar metallicity counterparts due to the dearth of metals in their atmospheres. Subdwarfs are halo members with high proper motions and large heliocentric velocities. They are important tracers of the chemical enrichment history of the Galaxy and belong to the first generation of stars formed in the Galaxy (at least 10 billion years old).
modified: 2020-11-04T18:47:26.827Z
editorial note: Definition Provenance
  created: 2020-11-04T18:47:37.308Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:47:37.339Z

Stellar spectral types
created: 2018-09-13T17:13:21.000Z
modified: 2018-09-13T17:16:52.000Z
narrower: O stars
narrower: B stars
narrower: S stars
narrower: OB stars
alternative label: Morgan-Keenan spectral types
related: Morgan-Keenan classification
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar types
contributor: AAS Frey.Katie Admin
narrower: A stars
narrower: F stars
narrower: G stars
narrower: K stars
narrower: M stars
narrower: R stars

Radiative processes
created: 2018-09-13T19:59:36.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Molecular physics
broader: Atomic physics
modified: 2020-12-16T19:42:28.753Z

Charge exchange ionization
created: 2018-09-13T19:59:40.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Ionization
preferred label: Charge exchange ionisation
modified: 2021-09-27T15:42:34.489Z

Radiative recombination
created: 2018-09-13T19:59:46.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Recombination
contributor: AAS Frey.Katie
definition: The process by which an ionized atom binds a free electron in a plasma to produce a new atomic state with the subsequent radiation of photons.
modified: 2020-11-17T20:04:35.039Z
modified: 2020-11-17T20:04:44.568Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T20:04:44.543Z

Molecular physics
created: 2018-09-13T19:59:51.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Laboratory astrophysics
contributor: AAS Frey.Katie Admin
narrower: Collision physics
narrower: De-excitation rates
narrower: Excitation rates
narrower: Radiative processes
narrower: Spectral line identification
related: Molecular spectroscopy
narrower: Molecular reactions
narrower: Polycyclic aromatic hydrocarbons
narrower: Complex organic molecules
narrower: Fullerenes
narrower: Metal-containing molecules
narrower: Molecular data
modified: 2022-06-11T22:58:45.858Z
narrower: Small molecules

Electron impact ionization
created: 2018-09-13T19:59:55.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Ionization
preferred label: Electron impact ionisation
alternative label: Electron-impact ionization
modified: 2022-06-11T21:49:55.564Z

Photoionization
created: 2018-09-13T19:59:59.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Ionization
modified: 2021-09-27T15:43:15.510Z
definition: The physical process in which an incident high-energy photon ejects one or more electrons from an atom, ion, or molecule.
preferred label: Photoionisation
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:30:27.531Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:30:27.559Z
contributor: AAS Frey.Katie

Dielectronic recombination
created: 2018-09-13T20:00:02.000Z
modified: 2018-09-21T18:05:25.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Recombination

Charge exchange recombination
created: 2018-09-13T20:00:07.000Z
modified: 2018-09-20T14:54:28.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Recombination

Atomic physics
created: 2018-09-13T20:00:34.000Z
broader: Laboratory astrophysics
creator: AAS Frey.Katie Admin
type: Concept
related: Atomic interferometry
narrower: Atomic data benchmarking
narrower: Collision physics
narrower: De-excitation rates
narrower: Excitation rates
narrower: Isotope shifts
narrower: Spectral line identification
narrower: Transition probabilities
narrower: Radiative processes
related: Atomic spectroscopy
narrower: Atomic data
narrower: Atomic reactions
contributor: AAS Frey.Katie Admin
modified: 2022-06-11T21:50:45.693Z

Atomic data benchmarking
created: 2018-09-13T20:00:40.000Z
modified: 2018-09-20T14:45:50.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Atomic physics
contributor: AAS Frey.Katie Admin

Collision physics
created: 2018-09-13T20:00:44.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Atomic physics
contributor: AAS Frey.Katie Admin
broader: Molecular physics
narrower: Charge transfer
narrower: Electron impact excitation
narrower: Mutual neutralization
definition: The physical interactions of atoms and molecules when they are brought into close contact with each other and with electrons, protons, neutrons or ions. This includes energy-conserving elastic scattering and inelastic scattering. Such collisions are an important probe of the structure and properties of matter.
modified: 2022-06-15T19:08:45.044Z
modified: 2022-06-15T19:09:26.354Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2022-06-15T19:09:26.345Z
  comment: Adapted from Nature Subjects, https://www.nature.com/subjects/atomic-and-molecular-collision-processes

De-excitation rates
created: 2018-09-13T20:00:48.000Z
modified: 2018-09-20T15:00:14.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Atomic physics
contributor: AAS Frey.Katie Admin
broader: Molecular physics

Excitation rates
created: 2018-09-13T20:00:52.000Z
modified: 2018-09-20T15:00:21.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Atomic physics
contributor: AAS Frey.Katie Admin
broader: Molecular physics

Ionization
created: 2018-09-13T20:00:57.000Z
creator: AAS Frey.Katie Admin
type: Concept
narrower: Charge exchange ionization
narrower: Electron impact ionization
narrower: Photoionization
definition: The process by which ions are produced, typically occurring by interaction with electromagnetic radiation ('photoionization'), or by collisions with atoms or electrons ('collisional ionization').
preferred label: Ionisation
contributor: AAS Frey.Katie Admin
broader: Atomic reactions
broader: Molecular reactions
modified: 2022-06-11T21:56:40.574Z
modified: 2020-11-10T17:57:04.584Z
editorial note: Definition Provenance
  created: 2020-11-10T17:57:04.556Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Isotope shifts
created: 2018-09-13T20:01:01.000Z
modified: 2018-09-20T14:48:13.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Atomic physics
contributor: AAS Frey.Katie Admin

Recombination
created: 2018-09-13T20:01:14.000Z
creator: AAS Frey.Katie Admin
type: Concept
narrower: Radiative recombination
narrower: Charge exchange recombination
narrower: Dielectronic recombination
narrower: Radical-radical recombination
definition: The capture of an electron by a positive ion. It is the inverse process to ionization.
broader: Atomic reactions
contributor: AAS Frey.Katie Admin
modified: 2022-06-11T22:58:45.859Z
contributor: AAS Frey.Katie
modified: 2020-11-17T20:16:24.528Z
editorial note: Definition Provenance
  created: 2020-11-17T20:16:24.498Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Spectral line identification
created: 2018-09-13T20:01:18.000Z
modified: 2018-09-20T15:01:44.000Z
creator: AAS Frey.Katie Admin
type: Concept
alternative label: Wavelength identification
broader: Atomic physics
contributor: AAS Frey.Katie Admin
broader: Molecular physics

Transition probabilities
created: 2018-09-13T20:01:23.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Atomic physics
contributor: AAS Frey.Katie Admin
definition: The probability that a quantum-mechanical system will make a transition from a given initial state to a given final state.
modified: 2020-11-04T22:00:57.049Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T22:01:11.893Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T22:01:11.919Z

Nuclear physics
created: 2018-09-13T20:01:59.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Laboratory astrophysics
narrower: Nuclear reaction cross sections
related: Nuclear astrophysics
contributor: AAS Frey.Katie
definition: The branch of physics which is concerned with the study of atomic nuclei, subatomic particles, and their exploitation.
modified: 2020-11-10T19:44:18.081Z
narrower: Nuclear decay
editorial note: Definition Provenance
  created: 2020-11-10T19:44:28.135Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T19:44:28.162Z

Experimental techniques
created: 2018-09-13T20:02:03.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Laboratory astrophysics
narrower: Mass spectrometry
narrower: Spectroscopy
modified: 2022-06-11T21:53:30.845Z
narrower: Molecular beams
narrower: Ion trapping
narrower: Ion-storage rings
narrower: Production techniques

Pre-biotic astrochemistry
created: 2018-09-13T20:02:08.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astrochemistry
related: Astrobiology
alternative label: Prebiotic astrochemistry
contributor: AAS Frey.Katie
alternative label: Pre-biotic chemistry
alternative label: Prebiotic chemistry
modified: 2020-10-26T21:40:47.030Z

Reaction catalysts
created: 2018-09-13T20:02:13.000Z
modified: 2018-09-20T15:07:24.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Astrochemistry

Reaction rates
created: 2018-09-13T20:02:17.000Z
modified: 2018-09-20T15:07:43.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Astrochemistry

Spectral line lists
created: 2018-09-13T20:02:20.000Z
modified: 2018-09-20T15:08:07.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
related: Laboratory astrophysics
broader: Astrochemistry

Collisional broadening
created: 2018-09-13T20:02:24.000Z
modified: 2018-09-20T15:35:52.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Atomic spectroscopy
broader: Molecular spectroscopy

Line intensities
created: 2018-09-13T20:02:28.000Z
modified: 2018-09-20T15:35:37.000Z
creator: AAS Frey.Katie Admin
type: Concept
alternative label: Line lifetimes
broader: Atomic spectroscopy
contributor: AAS Frey.Katie Admin
broader: Molecular spectroscopy

Line positions
created: 2018-09-13T20:02:33.000Z
modified: 2018-09-20T15:35:44.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Atomic spectroscopy
broader: Molecular spectroscopy

Nuclear reaction cross sections
created: 2018-09-13T20:03:50.000Z
modified: 2018-09-20T14:56:17.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Nuclear physics

Particle physics
created: 2018-09-13T20:03:54.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Laboratory astrophysics
related: Particle astrophysics
contributor: AAS Frey.Katie
definition: The branch of physics that deals with the smallest known structures of matter and energy in order to understand the fundamental particles and forces of nature.
modified: 2020-11-17T19:17:38.696Z
modified: 2020-11-17T19:17:48.715Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:17:48.690Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Plasma physics
created: 2018-09-13T20:04:00.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Laboratory astrophysics
related: Plasma astrophysics
modified: 2020-11-17T19:36:02.584Z
contributor: AAS Frey.Katie
definition: The study of the physical properties of the various forms of plasmas and their processing.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:36:12.540Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:36:12.570Z

Solid matter physics
created: 2018-09-13T20:04:05.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Laboratory astrophysics
related: Interstellar dust
alternative label: Dust and ices astrophysics
alternative label: Dust and ices physics
related: Astrophysical dust processes
related: Interstellar dust processes
alternative label: Condensed matter physics
narrower: Ice physics
narrower: Dust physics
modified: 2022-06-11T21:59:24.844Z
narrower: Mineral physics

Ice destruction
created: 2018-09-13T20:04:10.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Ice physics
modified: 2022-06-11T21:59:19.841Z

Ice formation
created: 2018-09-13T20:04:14.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Ice physics
modified: 2022-06-11T21:59:24.844Z

Theoretical techniques
created: 2018-09-13T20:04:19.000Z
modified: 2018-09-20T15:04:57.000Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
broader: Laboratory astrophysics
narrower: Reaction models
narrower: Quantum-chemical calculations

Mass spectrometry
created: 2018-09-13T20:04:23.000Z
creator: AAS Frey.Katie Admin
type: Concept
related: Mass spectrometers
definition: An analytical technique for identification of chemical structures, determination of mixtures, and quantitative elemental analysis, in which ions are separated according to the mass/charge ratio and detected by a suitable detector.
broader: Experimental techniques
contributor: AAS Frey.Katie Admin
narrower: Quadrupole mass spectrometry
narrower: Time-of-flight mass spectrometry
broader: Astronomical techniques
modified: 2022-06-11T21:53:05.143Z
editorial note: Definition Provenance
  created: 2020-11-10T19:19:09.740Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie
modified: 2020-11-10T19:19:09.767Z

Molecular spectroscopy
created: 2018-09-13T20:04:27.000Z
modified: 2018-09-20T15:35:52.000Z
narrower: Collisional broadening
creator: AAS Frey.Katie Admin
type: Concept
related: Molecular physics
narrower: Line positions
broader: Spectroscopy
contributor: AAS Frey.Katie Admin
narrower: High resolution spectroscopy
narrower: Line intensities
narrower: Photoelectron spectroscopy

High resolution spectroscopy
created: 2018-09-13T20:04:30.000Z
modified: 2018-09-21T18:09:24.000Z
broader: Molecular spectroscopy
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin

Photoelectron spectroscopy
created: 2018-09-13T20:04:34.000Z
modified: 2018-09-20T15:34:55.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Molecular spectroscopy
contributor: AAS Frey.Katie Admin

Asymptotic giant branch stars
created: 2018-09-13T21:08:20.000Z
modified: 2018-09-13T21:08:35.000Z
alternative label: AGB stars
related: Asymptotic giant branch
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar evolutionary types
contributor: AAS Frey.Katie Admin

Stellar granulation
created: 2018-09-14T16:58:41.000Z
modified: 2018-09-14T16:58:50.000Z
related: Solar granulation
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar physics
contributor: AAS Frey.Katie Admin

Field stars
created: 2018-09-14T19:11:19.000Z
related: Star clusters
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar types
related: Field of view
definition: A star that does not belong to a stellar cluster, but happens to be adjacent to it.
contributor: AAS Frey.Katie
modified: 2020-11-03T21:12:37.772Z
modified: 2020-11-03T21:12:54.257Z
editorial note: Definition Provenance
  created: 2020-11-03T21:12:54.226Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

B(e) stars
created: 2018-09-17T18:07:46.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Be stars
alternative label: B[e] stars
scope note: Not to be confused with Be stars. The concept should be written as B[e] star, the substitution or omission of square brackets is due to technical restrictions.
alternative label: B[e]-type stars
alternative label: B(e)-type stars
contributor: AAS Frey.Katie
definition: A Be star with forbidden lines in emission in its spectrum. B[e] stars show large infrared excess due to circumstellar dust emission.
modified: 2020-11-03T18:39:07.518Z
modified: 2020-11-03T18:39:20.215Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:39:20.188Z

CEMP stars
created: 2018-09-17T18:11:30.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Chemically peculiar stars
modified: 2020-10-26T19:34:27.131Z
alternative label: Carbon enhanced metal poor stars
definition: A star that presents very low iron abundances [Fe/H] < -4 but an anomalous richness in carbon. CEMP stars have been defined as a subset of metal-poor stars that exhibit elevated [C/Fe] ≥ +1.0. It has been recognized that ~15-20% of stars with [Fe/H] < -2.0 are carbon enhanced. This fraction rises to 30% for [Fe/H] < -3.0, to 40% for [Fe/H] < -3.5, and ~75% for [Fe/H] < -4.0. This increasing trend of CEMP-star frequency with declining [Fe/H] is confirmed by the observation of many thousands of CEMP stars.
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:34:38.220Z
modified: 2020-10-26T19:34:38.248Z

Gamma Doradus variable stars
created: 2018-09-17T18:57:47.000Z
modified: 2018-09-17T18:58:40.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Pulsating variable stars
alternative label: Gamma Dor
contributor: AAS Frey.Katie Admin
alternative label: γ Doradus
alternative label: γ Dor

History of astronomy
created: 2018-09-17T19:35:00.000Z
modified: 2018-09-17T19:35:11.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Interdisciplinary astronomy
contributor: AAS Frey.Katie Admin

Solar analogs
created: 2018-09-18T21:23:01.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Stellar types
contributor: AAS Frey.Katie Admin
alternative label: Solar-type stars
alternative label: Sun-like stars
related: The Sun
alternative label: Solar-like star
definition: A member of a class of unevolved or slightly evolved Population I disk stars with an effective temperature, degree of evolution, metallicity, and kinematic property not very different from those of the Sun.
preferred label: Solar analogues
modified: 2021-08-24T15:24:13.216Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:02:18.136Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T15:02:18.166Z

Anomalous Cepheid variable stars
created: 2018-09-20T14:39:45.000Z
modified: 2018-09-20T14:41:16.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Cepheid variable stars
contributor: AAS Frey.Katie Admin
alternative label: BL Boötis stars
alternative label: BL Boo stars
alternative label: BL Bootis stars

Atomic spectroscopy
created: 2018-09-20T15:13:17.000Z
modified: 2018-09-20T15:33:43.000Z
narrower: Line positions
narrower: Collisional broadening
creator: AAS Frey.Katie Admin
type: Concept
broader: Spectroscopy
contributor: AAS Frey.Katie Admin
related: Atomic physics
narrower: Line intensities

Shocks
created: 2018-09-20T16:50:00.000Z
narrower: Solar coronal mass ejection shocks
creator: AAS Frey.Katie Admin
type: Concept
broader: Plasma astrophysics
contributor: AAS Frey.Katie Admin
narrower: Interplanetary shocks
narrower: Planetary bow shocks
narrower: Stellar bow shocks
definition: A sharp change in the properties of a gas (density, pressure, temperature).
modified: 2020-11-04T14:50:40.116Z
modified: 2020-11-04T14:50:54.826Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:50:54.799Z

Theoretical models
created: 2018-09-20T16:53:29.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Laboratory astrophysics

Visible sources
created: 2018-09-20T21:22:19.000Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomical radiation sources
alternative label: Visible radiation sources
related: Optical astronomy
alternative label: Optical sources
modified: 2019-11-20T15:28:04.920Z
contributor: AAS Frey.Katie

The Unified Astronomy Thesaurus
modified: 2016-09-06T03:28:18.000Z
contributor: American-Institute-of-Physics
contributor: Bob-Shobbrook
contributor: Helen-Knudsen
contributor: Institute-of-Physics
contributor: International-Astronomical-Union
contributor: International-Virtual-Observatory-Alliance
contributor: Liz-Bryson
contributor: Marlene-Cummins
contributor: Rick-Hessman
contributor: Robyn-Shobbrook
description: The Unified Astronomy Thesaurus (UAT) is an open, interoperable and community-supported thesaurus which unifies existing, divergent, and isolated controlled vocabularies in astronomy and astrophysics into a single high-quality, freely-available open thesaurus formalizing astronomical concepts and their inter-relationships. The UAT builds upon the IAU Thesaurus with major contributions from the Astronomy portions of the thesauri developed by the Institute of Physics Publishing and the American Institute of Physics. The Unified Astronomy Thesaurus will be further enhanced and updated through a collaborative effort involving broad community participation.
publisher: American-Astronomical-Society
subject: Astronomy
type: ConceptScheme
has top concept: Astrophysical processes
has top concept: Observational astronomy
has top concept: Solar physics
has top concept: Solar system astronomy
has top concept: Stellar astronomy
has top concept: Cosmology
has top concept: Exoplanet astronomy
has top concept: Galactic and extragalactic astronomy
has top concept: High energy astrophysics
has top concept: Interdisciplinary astronomy
has top concept: Interstellar medium

Atomic interferometry
modified: 2018-09-20T16:49:15.000Z
type: Concept
alternative label: Atomic interferometry techniques
broader: Interferometry
contributor: AAS Frey.Katie Admin
alternative label: Atom interferometry
related: Atomic physics

Periodic variable stars
modified: 2018-08-30T20:08:36.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Variable stars
narrower: Multi-periodic variable stars
narrower: Short period variable stars
narrower: Long period variable stars

Population II Cepheid variable stars
modified: 2018-09-11T18:10:06.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Population II stars
alternative label: Population II Cepheid stars

PV Telescopii variable stars
modified: 2017-01-23T19:41:08.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: PV Telescopii
alternative label: PV Telescopii variables
broader: Pulsating variable stars

Quiescent solar prominence
modified: 2018-08-27T21:04:05.000Z
type: Concept
alternative label: Polar crown filament
broader: Solar prominences
related: Quiet sun
contributor: AAS Frey.Katie
broader: Solar filaments

Red straggler stars
modified: 2017-01-23T19:29:43.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Red stragglers
alternative label: Red-straggler stars
broader: Red giant stars

Late-type supergiant stars
modified: 2018-09-17T18:48:21.000Z
narrower: Red supergiant stars
type: Concept
alternative label: Cool supergiant stars
alternative label: Late-type supergiants
broader: Supergiant stars
broader: Late-type stars
narrower: K supergiant stars
narrower: M supergiant stars
contributor: AAS Frey.Katie Admin

Rotating shells
modified: 2016-11-02T13:45:24.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Circumstellar shells

RS Canum Venaticorum variable stars
modified: 2017-01-23T19:39:13.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: RS Canum Venaticorum
alternative label: RS Canum Venaticorum stars
alternative label: RS Canum Venaticorum variables
alternative label: RS-Canum Venaticorum variables
broader: Flare stars

Bediasites
modified: 2018-09-06T16:46:25.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Tektites

Beta Lyrae stars
modified: 2018-09-13T20:28:06.000Z
type: Concept
broader: Eclipsing binary stars
broader: Ellipsoidal variable stars
contributor: AAS Frey.Katie Admin
alternative label: Beta Lyrae variable stars

Solar spectral irradiance
modified: 2018-09-07T21:41:20.000Z
type: Concept
contributor: AAS Frey.Katie
alternative label: Solar irradiance
broader: Solar physics
alternative label: SSI

Solar spicules
modified: 2018-08-17T18:52:57.000Z
type: Concept
narrower: Solar mottles
narrower: Solar macrospicules
narrower: Solar fibrils
broader: Solar chromosphere
contributor: AAS Frey.Katie Admin

Stellar gas distribution
modified: 2016-11-02T15:38:03.000Z
contributor: AAS Frey.Katie Admin
type: Concept
broader: Stellar structures

Stellar inner cores
modified: 2017-01-23T20:19:56.000Z
contributor: AAS Frey.Katie Admin
type: Concept
broader: Stellar cores
scope note: Central region of stars

Stellar interiors
modified: 2016-11-02T15:11:30.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Stellar structures
narrower: Stellar cores
related: Solar interior

Stellar properties
modified: 2018-08-27T21:39:22.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Stellar characteristics
alternative label: Stellar magnitude
broader: Stellar physics
narrower: Starlight polarization
narrower: Stellar accretion
narrower: Stellar activity
narrower: Stellar ages
narrower: Stellar colors
narrower: Stellar effective temperatures
narrower: Stellar luminosities
narrower: Stellar magnetic fields
narrower: Stellar mass functions
narrower: Stellar masses
narrower: Stellar oscillations
narrower: Stellar radii
narrower: Stellar rotation
narrower: Stellar spectral lines
narrower: Expanding stellar envelopes

Substellar companion stars
modified: 2017-01-23T19:29:00.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Sub-stellar companion stars
alternative label: Sub-stellar companions
alternative label: Substellar companions
broader: Companion stars

SX Arietis variable stars
modified: 2017-01-23T19:27:10.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Helium variable stars
alternative label: SX Arietis stars
alternative label: SX Arietis variables
broader: Cataclysmic variable stars
broader: Dwarf novae
broader: Early-type variable stars
broader: Magnetic variable stars

SX Phoenicis variable stars
modified: 2018-08-31T16:52:37.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: SX Phoenicis stars
alternative label: SX Phoenicis variables
alternative label: SX-Phoenicis variables
broader: Multi-periodic variable stars

Young disk Cepheid variable stars
modified: 2017-01-23T19:43:35.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Young disc cepheid
alternative label: Young disk Cepheid stars
alternative label: Young disk Cepheid variables
alternative label: Young disk Cepheids
broader: Cepheid variable stars

Carbon flashes
modified: 2017-01-23T20:19:18.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: Carbon detonation
broader: Stellar evolution

Stellar convection envelopes
modified: 2018-08-27T21:36:49.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Stellar structures
narrower: Stellar convective shells
alternative label: Convective envelopes

Stellar convective shells
modified: 2018-08-27T21:38:07.000Z
type: Concept
broader: Stellar convection envelopes
contributor: AAS Frey.Katie
alternative label: Convective shells

Stellar convective zones
modified: 2018-08-27T21:37:33.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Stellar structures
related: Solar convective zone
alternative label: Convective zones
alternative label: Convection zones

Stellar coronal loops
modified: 2018-08-27T21:25:00.000Z
type: Concept
broader: Stellar coronae
contributor: AAS Frey.Katie
related: Solar coronal loops

Stellar phenomena
modified: 2018-08-17T18:57:16.000Z
type: Concept
broader: Stellar physics
narrower: Astrosphere interstellar medium interactions
narrower: Stellar flares
narrower: Stellar mass loss
narrower: Stellar pulsations
narrower: Burst astrophysics
contributor: AAS Frey.Katie Admin
narrower: Stellar coronal mass ejections

Dust shells
modified: 2016-11-02T13:44:36.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Circumstellar shells

Early-type supergiant stars
modified: 2017-01-23T19:50:18.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Early type supergiant stars
alternative label: Early-type supergiants
broader: Supergiant stars
broader: Early-type stars
narrower: O supergiant stars
narrower: OB supergiant stars
narrower: B supergiant stars
narrower: A supergiant stars

Early-type variable stars
modified: 2018-09-13T15:32:58.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Early type variable stars
broader: Early-type stars
narrower: Beta Cephei variable stars
narrower: SX Arietis variable stars
narrower: Luminous blue variable stars

Cosmochronology
modified: 2018-08-27T19:15:58.000Z
type: Concept
alternative label: Nucleocosmochronology
contributor: AAS Frey.Katie
broader: Cosmochemistry

Exoplanet dynamics
modified: 2018-09-13T16:52:47.000Z
type: Concept
broader: Exoplanet astronomy
narrower: Exoplanet tides
contributor: AAS Frey.Katie Admin
narrower: Star-planet interactions

F stars
modified: 2018-09-13T17:14:46.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: Class F stars
alternative label: F-type stars
broader: Intermediate-type stars
narrower: F dwarf stars
narrower: F giant stars
narrower: F subdwarf stars
narrower: F subgiant stars
narrower: F supergiant stars
related: Stellar classification
broader: Stellar spectral types

F subdwarf stars
modified: 2018-09-13T17:04:24.000Z
contributor: AAS Frey.Katie Admin
broader: Subdwarf stars
type: Concept
alternative label: F subdwarfs
broader: F stars
alternative label: F-type subdwarf stars
alternative label: F-type subdwarfs

G dwarf stars
modified: 2018-09-13T17:06:26.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: G dwarfs
broader: G stars
alternative label: G-type dwarfs
alternative label: G-type main sequence stars
alternative label: G-type dwarf stars
broader: Dwarf stars

G subdwarf stars
modified: 2018-09-13T17:04:32.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: G subdwarfs
broader: G stars
alternative label: G-type subdwarf stars
alternative label: G-type subdwarfs
broader: Subdwarf stars

A subdwarf stars
modified: 2018-09-13T17:04:07.000Z
type: Concept
alternative label: A subdwarfs
broader: A stars
alternative label: A-type subdwarfs
alternative label: A-type subdwarf stars
broader: Subdwarf stars
contributor: AAS Frey.Katie Admin

Gamma-ray lines
modified: 2018-02-06T19:49:31.000Z
type: Concept
alternative label: Gamma ray line
broader: Gamma-rays
contributor: AAS Frey.Katie
alternative label: Gamma ray lines

H I line emission
modified: 2018-09-07T20:53:11.000Z
type: Concept
alternative label: 21 cm lines
alternative label: 21-cm line emissions
alternative label: 21-cm lines
alternative label: H I lines
alternative label: HI line
alternative label: Hydrogen lines
broader: Interstellar line emission
contributor: AAS Frey.Katie
alternative label: H1 line emission

Helmholtz-Kelvin contraction
modified: 2018-09-13T15:12:38.000Z
type: Concept
alternative label: Helmholtz Kelvin contraction
alternative label: Helmholtz-Kelvin mechanism
alternative label: Kelvin-Helmholtz contraction
related: Pre-main sequence
contributor: AAS Frey.Katie
broader: Stellar evolution

Astrophysical fluid dynamics
modified: 2018-08-27T19:37:19.000Z
type: Concept
broader: Interdisciplinary astronomy
contributor: AAS Frey.Katie
narrower: Internal waves
narrower: Hydrodynamics
narrower: Magnetohydrodynamics
narrower: Radiative magnetohydrodynamics

Interacting binary stars
modified: 2018-08-30T19:52:22.000Z
type: Concept
broader: Close binary stars
contributor: AAS Frey.Katie
narrower: Compact binary stars
narrower: Semi-detached binary stars
narrower: Symbiotic binary stars
narrower: Contact binary stars
narrower: Common envelope binary stars
narrower: Stellar mergers

Intermediate-type stars
modified: 2018-09-17T19:46:54.000Z
type: Concept
alternative label: Intermediate stars
contributor: AAS Frey.Katie Admin
narrower: F stars
narrower: G stars
alternative label: Intermediate type stars
broader: Stellar types

Gamma Cassiopeiae stars
modified: 2018-09-13T16:43:49.000Z
type: Concept
broader: Emission line stars
contributor: AAS Frey.Katie Admin
broader: Eruptive variable stars

K dwarf stars
modified: 2018-09-13T17:08:42.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: K dwarfs
broader: K stars
broader: Late-type dwarf stars
alternative label: K-type dwarfs
alternative label: K-type main sequence stars
alternative label: K-type dwarf stars
broader: Dwarf stars

K supergiant stars
modified: 2018-09-17T18:48:39.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: K supergiants
broader: K stars
broader: Late-type supergiant stars
alternative label: K-type supergiant stars
alternative label: K-type supergiants
related: Red supergiant stars

Late-type dwarf stars
modified: 2017-01-23T19:47:36.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Cool dwarf stars
alternative label: Late-type dwarfs
broader: Late-type stars
narrower: T dwarfs
narrower: K dwarf stars
narrower: L dwarfs
narrower: M dwarf stars
modified: 2018-02-06T18:21:29.000Z
editorial note: continuation of deprecate? note
  created: 2018-02-06T18:21:29.000Z
  creator: AAS Frey.Katie
  comment: Instead, concept could possibly be renamed "late type dwarfs" as not all child concepts are stars.
editorial note: deprecate?
  created: 2018-02-06T18:20:46.000Z
  creator: AAS Frey.Katie
  comment: This concept should possibly be deprecated? At the very least "L" and "T" type dwarf stars should be removed as child concepts, as those are both actually brown dwarfs, which are not stars.

Late-type giant stars
modified: 2017-01-23T19:48:12.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Cool giant stars
alternative label: Late type giant stars
alternative label: Late-type giants
broader: Giant stars
broader: Late-type stars
narrower: Mira variable stars
narrower: Semi-regular variable stars
narrower: Heavy metal stars
narrower: Irregular variable stars
narrower: K giant stars
narrower: M giant stars
related: Carbon stars

M supergiant stars
modified: 2018-09-17T18:48:31.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: M supergiants
broader: Late-type supergiant stars
broader: M stars
alternative label: M-type supergiant stars
alternative label: M-type supergiants
related: Red supergiant stars

High time resolution astrophysics
modified: 2018-09-18T20:17:30.000Z
type: Concept
alternative label: HTRA
broader: Astronomical techniques
alternative label: High time resolution astronomy
contributor: AAS Frey.Katie Admin

Stellar structures
modified: 2018-08-27T21:39:00.000Z
contributor: AAS Frey.Katie
type: Concept
broader: Stellar physics
narrower: Polytropes
narrower: Stellar gas distribution
narrower: Stellar interiors
narrower: Stellar surfaces
narrower: Strömgren spheres
narrower: Circumstellar shells
narrower: Stellar convection envelopes
narrower: Stellar convective zones

Ae stars
modified: 2018-02-06T18:04:54.000Z
type: Concept
broader: Early-type emission stars
broader: A stars
narrower: Herbig Ae/Be stars
contributor: AAS Frey.Katie
alternative label: Ae-type stars

A subgiant stars
modified: 2018-02-06T18:06:12.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: A subgiants
broader: Subgiant stars
broader: A stars
alternative label: A-type subgiants
alternative label: A-type subgiant stars

A giant stars
modified: 2018-02-06T18:07:06.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: A giants
broader: A stars
broader: Giant stars
alternative label: A-type giants
alternative label: A-type giant stars

B giant stars
modified: 2018-02-06T18:08:00.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: B giants
broader: B stars
broader: Giant stars
alternative label: B-type giant stars
alternative label: B-type giants

Bp stars
modified: 2018-02-06T18:08:07.000Z
type: Concept
broader: B stars
broader: Chemically peculiar stars
broader: Magnetic stars
contributor: AAS Frey.Katie
alternative label: Bp-type stars

Oef stars
modified: 2018-02-06T18:09:48.000Z
type: Concept
broader: O stars
broader: Early-type emission stars
contributor: AAS Frey.Katie
alternative label: Oef-type stars

Oe stars
modified: 2018-02-06T18:09:54.000Z
type: Concept
broader: O stars
broader: Early-type emission stars
contributor: AAS Frey.Katie
alternative label: Oe-type stars

WCN stars
modified: 2018-02-06T18:10:12.000Z
type: Concept
broader: Wolf-Rayet stars
contributor: AAS Frey.Katie
alternative label: WCN-type stars

OB supergiant stars
modified: 2018-02-06T18:11:10.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: OB supergiants
broader: OB stars
broader: Early-type supergiant stars
alternative label: OB-type supergiant stars
alternative label: OB-type supergiants

O giant stars
modified: 2018-02-06T18:12:03.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: O giants
broader: O stars
broader: Giant stars
alternative label: O-type giant stars
alternative label: O-type giants

O supergiant stars
modified: 2018-02-06T18:12:46.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: O supergiants
broader: O stars
broader: Early-type supergiant stars
alternative label: O-type supergiant stars
alternative label: O-type supergiants

F dwarf stars
modified: 2018-09-13T20:15:57.000Z
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: F dwarfs
broader: F stars
alternative label: F-type dwarf stars
alternative label: F-type dwarfs
broader: Dwarf stars

F giant stars
modified: 2018-02-06T18:13:34.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: F giants
broader: F stars
broader: Giant stars
alternative label: F-type giant stars
alternative label: F-type giants

F subgiant stars
modified: 2018-02-06T18:13:59.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: F subgiants
broader: Subgiant stars
broader: F stars
alternative label: F-type subgiant stars
alternative label: F-type subgiants

F supergiant stars
modified: 2018-02-06T18:14:16.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: F supergiants
broader: Supergiant stars
broader: F stars
narrower: UU Herculis stars
alternative label: F-type supergiants
alternative label: F-type supergiant stars

G giant stars
modified: 2018-02-06T18:14:59.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: G giants
broader: G stars
broader: Giant stars
alternative label: G-type giant stars
alternative label: G-type giants

G subgiant stars
modified: 2018-02-06T18:15:26.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: G subgiants
broader: Subgiant stars
broader: G stars
alternative label: G-type subgiant stars
alternative label: G-type subgiants

G supergiant stars
modified: 2018-02-06T18:15:39.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: G supergiants
broader: Supergiant stars
broader: G stars
alternative label: G-type supergiant stars
alternative label: G-type supergiants

K subdwarf stars
modified: 2018-02-06T18:16:52.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: K subdwarfs
broader: K stars
alternative label: K-type subdwarf stars
alternative label: K-type subdwarfs

K subgiant stars
modified: 2018-02-06T18:17:10.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: K subgiants
broader: Subgiant stars
broader: K stars
alternative label: K-type subgiant stars
alternative label: K-type subgiants

M giant stars
modified: 2018-02-06T18:26:28.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: M giants
broader: Late-type giant stars
broader: M stars
narrower: Me variable stars
alternative label: M-type giants
alternative label: M-type giant stars

Me variable stars
modified: 2018-09-14T15:27:48.000Z
type: Concept
broader: M giant stars
scope note: Used for the subset of Me stars that are variable stars. Not all Me stars are variable stars.
alternative label: Me-type variables
alternative label: Me-type variable stars
alternative label: Me variables
contributor: AAS Frey.Katie Admin
broader: Me stars

M subdwarf stars
modified: 2018-02-06T18:27:53.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: M subdwarfs
broader: M stars
alternative label: M-type subdwarf stars
alternative label: M-type subdwarfs

M subgiant stars
modified: 2018-02-06T18:28:07.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: M subgiants
broader: Subgiant stars
broader: M stars
alternative label: M-type subgiant stars
alternative label: M-type subgiants

N stars
modified: 2018-02-06T18:28:47.000Z
type: Concept
broader: Carbon stars
broader: Late-type stars
contributor: AAS Frey.Katie
alternative label: N-type stars

Solar energetic particles
modified: 2018-02-06T18:48:28.000Z
type: Concept
alternative label: Energetic solar particles
alternative label: Suprathermal particles
broader: Solar particle emission
broader: Interplanetary physics
contributor: AAS Frey.Katie
broader: Solar storm

Solar flares
contributor: AAS Frey.Katie Admin
type: Concept
broader: Solar activity
broader: Solar physics
narrower: Solar radio flares
narrower: Solar x-ray flares
related: Stellar flares
broader: Solar storm
narrower: Solar flare spectra
narrower: Solar white-light flares
definition: A bright eruption form the Sun's chromosphere in the vicinity of a sunspot. Solar flares are caused by tremendous explosions on the surface of the Sun. In a matter of just a few minutes they heat the material to many millions of degrees and release as much energy as a billion megatons of TNT.
modified: 2020-11-24T17:38:19.329Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:21:36.530Z
modified: 2020-11-04T15:21:36.554Z

Solar storm
modified: 2018-02-06T18:49:48.000Z
type: Concept
broader: Solar activity
contributor: AAS Frey.Katie
narrower: Solar energetic particles
narrower: Solar coronal mass ejections
narrower: Solar flares

Soft gamma-ray repeaters
modified: 2018-02-06T19:50:29.000Z
type: Concept
alternative label: Soft gamma repeaters
broader: Gamma-ray sources
broader: Irregular variable stars
broader: Magnetars
contributor: AAS Frey.Katie
alternative label: Soft gamma ray repeaters

Solar gamma-ray emission
modified: 2018-02-06T19:50:42.000Z
type: Concept
alternative label: Solar γ-ray emission
broader: Solar electromagnetic emission
contributor: AAS Frey.Katie
alternative label: Solar gamma ray emission

Stellar granules
modified: 2018-09-14T15:23:12.000Z
type: Concept
broader: Stellar photospheres
alternative label: Stellar granule
contributor: AAS Frey.Katie Admin
related: Solar granules

Galaxy stellar disks
modified: 2018-08-17T17:21:32.000Z
type: Concept
broader: Galaxy disks
contributor: AAS Frey.Katie
alternative label: Stellar disks
scope note: Refers to the disk of stars that make up part of the disk of the galaxy. This concept would specific exclude the dust and gas components of the galaxy's disk.

Multiple mirror telescopes
modified: 2018-08-17T16:38:16.000Z
type: Concept
alternative label: MM
broader: Optical telescopes
contributor: AAS Frey.Katie

Galaxy nuclei
modified: 2018-08-17T17:19:39.000Z
type: Concept
narrower: Active galactic nuclei
narrower: Galaxy circumnuclear disk
contributor: AAS Frey.Katie
broader: Galaxy structure

Solar transition region
modified: 2018-08-27T21:14:20.000Z
type: Concept
contributor: AAS Frey.Katie
scope note: The region of the Sun's atmosphere between the chromosphere and corona.
broader: Solar corona
broader: Solar chromosphere

Stellar mass loss
modified: 2018-08-17T18:56:43.000Z
type: Concept
broader: Stellar phenomena
narrower: Plasma jets
related: Stellar jets
related: Solar coronal mass ejections
contributor: AAS Frey.Katie Admin
related: Stellar coronal mass ejections

Ejecta
contributor: AAS Frey.Katie
type: Concept
broader: Stellar remnants
related: Supernovae
related: Solar coronal mass ejections
related: Stellar coronal mass ejections
definition: Material, in solid, liquid, or gaseous form, thrown out by a stellar body, especially as a result of supernova explosion.
modified: 2020-11-03T20:48:45.494Z
modified: 2020-11-03T20:49:00.871Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T20:49:00.836Z
  comment: Modified from an Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Hydrodynamical simulations
modified: 2018-08-27T19:37:19.000Z
type: Concept
alternative label: Magneto-hydrodynamic simulations
contributor: AAS Frey.Katie
related: Hydrodynamics
broader: Astronomical simulations

Astroinformatics
modified: 2018-08-27T19:21:00.000Z
type: Concept
contributor: AAS Frey.Katie
broader: Interdisciplinary astronomy

N-body simulations
modified: 2018-08-27T19:24:15.000Z
type: Concept
broader: Gravitational interaction
related: N-body problem
contributor: AAS Frey.Katie
broader: Astronomical simulations

Analytical mathematics
modified: 2018-09-06T15:26:34.000Z
type: Concept
narrower: Perturbation methods
narrower: Radiative transfer equation
narrower: von Zeipel theorem
narrower: Astronomical models
narrower: Luminosity function
contributor: AAS Frey.Katie
related: Computational astronomy
broader: Astronomical techniques

Virtual observatories
modified: 2018-08-27T19:29:50.000Z
broader: Observatories
type: Concept
example: World Wide Telescope
contributor: AAS Frey.Katie
broader: Astronomy web services

Ephemeral active regions
modified: 2018-08-27T19:48:50.000Z
type: Concept
broader: Sunspots
contributor: AAS Frey.Katie
broader: Solar active regions

Solar radio flares
modified: 2018-08-27T21:02:15.000Z
type: Concept
broader: Solar flares
contributor: AAS Frey.Katie

Solar x-ray flares
modified: 2018-08-27T21:02:26.000Z
type: Concept
broader: Solar flares
related: X-ray sources
contributor: AAS Frey.Katie

Solar mottles
modified: 2018-08-27T21:07:15.000Z
type: Concept
broader: Solar spicules
contributor: AAS Frey.Katie

F layer
modified: 2018-08-27T21:12:22.000Z
type: Concept
alternative label: Appleton layer
scope note: Earth upper atmosphere
contributor: AAS Frey.Katie
broader: Earth ionosphere

Stellar chromospheres
modified: 2018-08-27T21:55:24.000Z
type: Concept
broader: Stellar atmospheres
contributor: AAS Frey.Katie
related: Solar chromosphere
alternative label: Chromospheres

Helioseismic pulsations
modified: 2018-08-27T21:30:16.000Z
type: Concept
broader: Helioseismology
contributor: AAS Frey.Katie
broader: Solar oscillations
broader: Solar interior

Stellar oscillations
modified: 2018-08-27T21:21:54.000Z
type: Concept
broader: Stellar properties
broader: Asteroseismology
narrower: Rapid stellar oscillations
contributor: AAS Frey.Katie
related: Solar oscillations

Solar coronal transients
modified: 2018-09-07T17:40:31.000Z
type: Concept
contributor: AAS Frey.Katie
broader: Solar corona

Stellar coronal dimming
modified: 2018-08-27T21:24:30.000Z
type: Concept
broader: Stellar coronae
contributor: AAS Frey.Katie

Solar oscillations
modified: 2018-08-27T21:31:38.000Z
type: Concept
broader: Solar physics
contributor: AAS Frey.Katie
related: Stellar oscillations
narrower: Helioseismic pulsations

Solar particle emission
modified: 2018-08-27T21:31:34.000Z
type: Concept
broader: Solar physics
narrower: Solar energetic particles
narrower: Solar neutrons
related: Solar neutrinos
contributor: AAS Frey.Katie
narrower: Solar coronal mass ejection shocks

Stellar magnetic fields
modified: 2018-08-27T21:39:45.000Z
type: Concept
alternative label: Stellar magnetospheres
broader: Stellar properties
broader: Asteroseismology
contributor: AAS Frey.Katie
related: Solar magnetic fields

Stellar mass functions
modified: 2018-08-27T21:40:07.000Z
type: Concept
alternative label: IMF
broader: Stellar properties
contributor: AAS Frey.Katie
related: Stellar masses

Stellar masses
modified: 2018-08-27T21:40:07.000Z
type: Concept
broader: Stellar properties
contributor: AAS Frey.Katie
related: Solar mass
related: Stellar mass functions

Solar core
modified: 2018-08-27T21:43:18.000Z
type: Concept
broader: Solar interior
contributor: AAS Frey.Katie
related: Stellar cores

Stellar cores
modified: 2018-08-27T21:43:18.000Z
type: Concept
broader: Stellar interiors
narrower: Stellar inner cores
contributor: AAS Frey.Katie
related: Solar core

Isotopic abundances
modified: 2018-08-27T21:45:06.000Z
type: Concept
broader: Chemical abundances
contributor: AAS Frey.Katie

Overabundances
modified: 2018-08-27T21:45:36.000Z
type: Concept
broader: Chemical abundances
contributor: AAS Frey.Katie

Stellar activity
modified: 2018-08-27T21:51:14.000Z
type: Concept
broader: Stellar properties
contributor: AAS Frey.Katie
related: Solar activity

Stellar faculae
modified: 2018-08-27T21:51:27.000Z
type: Concept
alternative label: Stellar facula
broader: Stellar photospheres
contributor: AAS Frey.Katie
related: Solar faculae

Solar surface
modified: 2018-08-27T21:52:34.000Z
type: Concept
broader: Solar physics
contributor: AAS Frey.Katie
related: Stellar surfaces

Stellar surfaces
modified: 2018-08-27T21:52:34.000Z
type: Concept
broader: Stellar structures
contributor: AAS Frey.Katie
related: Solar surface

Solar chromosphere
modified: 2018-08-27T21:55:24.000Z
type: Concept
broader: Solar atmosphere
narrower: Plages
narrower: Active solar chromosphere
narrower: Alfven waves
narrower: Solar spicules
contributor: AAS Frey.Katie
narrower: Ellerman Bombs
narrower: Quiet solar chromosphere
narrower: Solar chromospheric heating
narrower: Solar transition region
related: Stellar chromospheres

Stellar photospheres
modified: 2018-08-27T21:55:36.000Z
type: Concept
broader: Stellar atmospheres
narrower: Stellar faculae
narrower: Stellar granules
contributor: AAS Frey.Katie
alternative label: Photospheres
related: Solar photosphere

Solar electromagnetic emission
modified: 2018-08-29T14:50:05.000Z
type: Concept
broader: Solar physics
narrower: Solar extreme ultraviolet emission
narrower: Solar gamma-ray emission
narrower: Solar radio emission
narrower: Solar ultraviolet emission
narrower: Solar x-ray emission
contributor: AAS Frey.Katie
related: Spectropolarimetry

X-ray point sources
modified: 2018-08-29T18:45:15.000Z
type: Concept
broader: X-ray sources
contributor: AAS Frey.Katie

Solar interior
modified: 2018-08-29T20:20:32.000Z
type: Concept
broader: Solar physics
narrower: Solar core
related: Stellar interiors
contributor: AAS Frey.Katie
narrower: Solar meridional circulation
narrower: Solar differential rotation
narrower: Solar convective zone
narrower: Solar radiative zone
narrower: Helioseismic pulsations
related: Helioseismology

Algol variable stars
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: Beta persei stars
broader: Eclipsing binary stars
broader: Semi-detached binary stars
alternative label: Algol-type variables
modified: 2020-11-05T19:59:26.109Z

W Ursae Majoris variable stars
modified: 2018-08-30T20:01:47.000Z
type: Concept
alternative label: W Ursae Majoris variables
broader: Contact binary stars
contributor: AAS Frey.Katie
broader: Eclipsing binary stars

Ellipsoidal variable stars
modified: 2018-09-14T15:24:19.000Z
type: Concept
alternative label: Ellipsoidal binary stars
broader: Close binary stars
broader: Extrinsic variable stars
narrower: Beta Lyrae stars
contributor: AAS Frey.Katie Admin
narrower: FK Comae stars

Lc variable stars
modified: 2018-08-30T20:03:55.000Z
type: Concept
broader: Irregular variable stars
contributor: AAS Frey.Katie

Peculiar variable stars
modified: 2018-08-30T20:06:20.000Z
type: Concept
broader: Chemically peculiar stars
contributor: AAS Frey.Katie
broader: Variable stars

Slow irregular variable stars
modified: 2018-08-30T20:54:18.000Z
contributor: AAS Frey.Katie
type: Concept
alternative label: Slow irregular variables
alternative label: Slow irregulars
broader: Long period variable stars
narrower: Lb variable stars

Lb variable stars
modified: 2018-08-30T20:54:18.000Z
broader: Slow irregular variable stars
type: Concept
broader: Giant stars
contributor: AAS Frey.Katie
alternative label: TZ Cassiopeia stars
alternative label: TZ Cassiopeia

Milky Way dark matter halo
modified: 2018-08-30T21:01:50.000Z
type: Concept
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy dark matter halos

Galaxy stellar halos
modified: 2018-08-31T20:24:15.000Z
type: Concept
narrower: Stellar rings
contributor: AAS Frey.Katie
alternative label: Galaxy halos
broader: Galaxy structure
related: Milky Way stellar halo

Proplyds
modified: 2020-11-03T20:36:24.791Z
type: Concept
alternative label: Photo-evaporating protoplanetary disks
broader: Protoplanetary disks
definition: A circumstellar disk of dense gas and dust surrounding a young newly formed star, a T Tauri star or Herbig star. In particular, an externally ionized protoplanetary disk seen in emission in the Orion Nebula.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:36:36.399Z
editorial note: Definition Provenance
  created: 2020-11-03T20:36:36.374Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

T Tauri stars
modified: 2020-11-04T19:46:55.246Z
broader: Young stellar objects
type: Concept
alternative label: TT
broader: Emission line stars
broader: Irregular variable stars
narrower: Weak-line T Tauri stars
narrower: Classical T Tauri stars
related: FU Orionis stars
contributor: AAS Frey.Katie Admin
definition: A member of a class of young stellar objects of roughly 1 solar mass showing strong infrared excess emission attributed to circumstellar disks and found within or close to molecular clouds. T Tauri stars are protostars in the final stages of formation to become a stable main sequence star. The nuclear reactions in their core have not yet stabilized and the stars are known for the variability of their brightness.
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T19:47:11.226Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T19:47:11.263Z

Milky Way rotation
modified: 2018-08-31T20:22:14.000Z
type: Concept
alternative label: Milky Way Galaxy rotation
alternative label: Rotation of the Milky Way
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy rotation

Galaxy rotation
modified: 2018-08-31T20:22:14.000Z
type: Concept
broader: Galaxy kinematics
narrower: Oort constants
narrower: Galaxy rotation curves
contributor: AAS Frey.Katie
related: Milky Way rotation

Milky Way mass
modified: 2018-08-31T20:22:25.000Z
type: Concept
alternative label: Mass of the Milky Way
alternative label: Milky Way Galaxy mass
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy masses

Galaxy masses
modified: 2018-08-31T20:22:25.000Z
type: Concept
broader: Galaxy properties
narrower: Galaxy mass distribution
contributor: AAS Frey.Katie
related: Milky Way mass

Milky Way magnetic fields
modified: 2018-08-31T20:22:34.000Z
type: Concept
alternative label: Magnetic fields in the Milky Way
alternative label: Milky Way Galaxy magnetic fields
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy magnetic fields

Galaxy magnetic fields
modified: 2018-08-31T20:22:34.000Z
type: Concept
broader: Galaxy properties
contributor: AAS Frey.Katie
related: Milky Way magnetic fields

Milky Way formation
modified: 2018-08-31T20:22:48.000Z
type: Concept
alternative label: Formation of the Milky Way
alternative label: Milky Way Galaxy formation
alternative label: Milky Way Galaxy origin
alternative label: Milky Way origin
alternative label: Origin of the Milky Way
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy formation

Milky Way evolution
modified: 2018-08-31T20:22:58.000Z
type: Concept
alternative label: Evolution of the Milky Way
alternative label: Milky Way Galaxy evolution
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy evolution

Galaxy evolution
modified: 2018-08-31T20:22:58.000Z
type: Concept
alternative label: Evolution of galaxies
alternative label: Galaxial evolution
broader: Cosmological evolution
broader: Galaxy processes
narrower: Galaxy chemical evolution
contributor: AAS Frey.Katie
related: Milky Way evolution
narrower: Galaxy quenching

Milky Way dynamics
modified: 2018-08-31T20:23:10.000Z
type: Concept
alternative label: Dynamics of the Milky Way
alternative label: Milky Way Galaxy dynamics
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy dynamics

Galaxy dynamics
modified: 2018-08-31T20:23:10.000Z
type: Concept
broader: Galaxy physics
broader: Galaxy processes
contributor: AAS Frey.Katie
related: Milky Way dynamics

Milky Way disk
modified: 2018-08-31T20:23:26.000Z
type: Concept
alternative label: Disc of the Milky Way
alternative label: Disk of the Milky Way
alternative label: Milky Way Galaxy disc
alternative label: Milky Way Galaxy disk
alternative label: Milky Way disc
alternative label: Milky Way galactic disc
alternative label: Milky Way galactic disk
broader: Milky Way Galaxy physics
contributor: AAS Frey.Katie
related: Galaxy disks

Galaxy disks
modified: 2018-08-31T20:23:26.000Z
type: Concept
narrower: Galaxy stellar disks
broader: Galaxy structure
scope note: Refers to the disk part of a galaxy. Does not refer to a specific shape and form of a particular classification of galaxies (see "Disk galaxies").
contributor: AAS Frey.Katie
related: Milky Way disk

Milky Way stellar halo
modified: 2018-08-31T20:24:15.000Z
type: Concept
alternative label: Galactic halo of the Milky Way
alternative label: Halo of the Milky Way
alternative label: Milky Way Galaxy halo
alternative label: Milky Way galactic halo
alternative label: Milky Way halo
broader: Milky Way Galaxy physics
related: Galaxy stellar halos
contributor: AAS Frey.Katie

Chemically peculiar giant stars
modified: 2018-09-04T20:21:05.000Z
type: Concept
broader: Chemically peculiar stars
broader: Giant stars
contributor: AAS Frey.Katie
alternative label: Peculiar giants
alternative label: Peculiar giant stars

Computational astronomy
modified: 2018-09-06T15:26:34.000Z
type: Concept
broader: Astronomical methods
narrower: Astronomy software
narrower: Astronomy data analysis
contributor: AAS Frey.Katie
broader: Interdisciplinary astronomy
narrower: Computational methods
related: Analytical mathematics

Faber-Jackson distance
modified: 2018-09-06T14:44:39.000Z
type: Concept
alternative label: Faber Jackson distance
broader: Stellar distance
editorial note: Used to measure distances to galaxies, not stars. This term should be moved.
contributor: AAS Frey.Katie
broader: Astronomical techniques

Astronomical site protection
modified: 2018-09-06T15:05:17.000Z
type: Concept
broader: Astronomical research
contributor: AAS Frey.Katie
related: Observatories

Sunyaev-Zeldovich effect
modified: 2018-09-06T15:15:41.000Z
type: Concept
alternative label: SZ effect
broader: Radio astronomy
contributor: AAS Frey.Katie
broader: Cosmic microwave background radiation

X-ray bursters
modified: 2018-09-06T16:23:46.000Z
type: Concept
broader: X-ray binary stars
related: X-ray bursts
contributor: AAS Frey.Katie
related: X-ray sources
broader: X-ray transient sources

Moldavites
modified: 2018-09-06T16:46:17.000Z
type: Concept
broader: Tektites
contributor: AAS Frey.Katie

Exoplanet atmospheres
modified: 2018-09-07T14:26:36.000Z
type: Concept
broader: Exoplanet structure
narrower: Exoplanet atmospheric variability
narrower: Exoplanet atmospheric composition
contributor: AAS Frey.Katie
related: Planetary atmospheres
narrower: Exoplanet atmospheric dynamics
narrower: Exoplanet atmospheric evolution
narrower: Exoplanet atmospheric structure

Stellar coronal lines
modified: 2018-09-07T17:36:36.000Z
type: Concept
broader: Stellar coronae
contributor: AAS Frey.Katie
related: Solar coronal lines

Stellar coronal plumes
modified: 2018-09-07T17:38:57.000Z
type: Concept
broader: Stellar coronae
contributor: AAS Frey.Katie
related: Solar coronal plumes

Dense interstellar clouds
modified: 2018-09-07T17:54:59.000Z
type: Concept
broader: Interstellar clouds
contributor: AAS Frey.Katie
alternative label: Dense clouds

Recombination (cosmology)
modified: 2018-09-07T20:34:15.000Z
type: Concept
broader: Big Bang theory
broader: Early universe
contributor: AAS Frey.Katie
narrower: Cosmic background radiation

Cosmic noise
modified: 2018-09-17T21:28:35.000Z
type: Concept
broader: Radio astronomy
narrower: Cosmic microwave background radiation
contributor: AAS Frey.Katie Admin

Cosmic microwave background radiation
modified: 2018-09-07T20:34:54.000Z
type: Concept
alternative label: CMB
alternative label: CMBR
alternative label: Cosmic microwave background
alternative label: MBR
alternative label: Relic radiation
broader: Cosmic noise
narrower: Cosmic anisotropy
narrower: Cosmic isotropy
related: Non-Gaussianity
related: CMBR detectors
contributor: AAS Frey.Katie
narrower: Sunyaev-Zeldovich effect
related: Redshifted
broader: Cosmic background radiation

Galaxy magnitudes
modified: 2018-09-07T22:02:58.000Z
type: Concept
alternative label: Galactic magnitudes and colours
broader: Galaxy properties
contributor: AAS Frey.Katie
broader: Magnitude

Elliptical orbits
modified: 2018-09-12T15:50:17.000Z
type: Concept
alternative label: Eccentric orbit
broader: Orbital elements
broader: Orbital motion
narrower: Major axis
narrower: Minor axis
narrower: Semimajor axis
narrower: Semiminor axis
contributor: AAS Frey.Katie
alternative label: Elliptical orbit

Delta Delphini variable stars
modified: 2018-09-12T16:14:07.000Z
type: Concept
broader: Pulsating variable stars
contributor: AAS Frey.Katie

Stellar evolutionary tracks
modified: 2018-09-13T14:52:07.000Z
type: Concept
narrower: Hayashi track
narrower: Henyey track
contributor: AAS Frey.Katie
broader: Stellar evolutionary models

Zero-age main sequence stars
modified: 2018-09-13T14:54:43.000Z
type: Concept
alternative label: ZAMS
alternative label: Zero-age main sequence
broader: Main sequence stars
related: Hertzsprung Russell diagram
contributor: AAS Frey.Katie
alternative label: Zero age main sequence
related: Main sequence

Extreme horizontal branch stars
modified: 2018-09-13T14:55:30.000Z
type: Concept
broader: Horizontal branch stars
contributor: AAS Frey.Katie
related: Horizontal branch

Protoclusters
modified: 2018-09-13T14:56:53.000Z
type: Concept
contributor: AAS Frey.Katie
broader: Star clusters

Pre-main sequence
modified: 2018-09-13T15:12:48.000Z
type: Concept
contributor: AAS Frey.Katie
broader: Hertzsprung Russell diagram
related: Helmholtz-Kelvin contraction
related: Pre-main sequence stars

Herbig Ae/Be stars
modified: 2018-09-13T16:30:21.000Z
type: Concept
alternative label: HAeBe stars
alternative label: Herbig Ae-Be stars
alternative label: Herbig stars
broader: Be stars
broader: Ae stars
contributor: AAS Frey.Katie Admin
broader: Young stellar objects

Neutron stars
modified: 2018-09-13T15:23:22.000Z
type: Concept
broader: Nuclear astrophysics
narrower: Neutron star cores
narrower: Pulsars
narrower: Relativistic stars
narrower: Magnetars
contributor: AAS Frey.Katie
broader: Compact objects

Nova-like variable stars
modified: 2018-09-13T15:49:58.000Z
type: Concept
alternative label: Nova-like variables
broader: Cataclysmic variable stars
narrower: UX Ursae Majoris stars
narrower: VY Sculptoris stars
contributor: AAS Frey.Katie Admin
broader: Stellar remnants

Stellar remnants
modified: 2018-09-13T15:28:10.000Z
type: Concept
alternative label: Late stage stellar evolution
alternative label: Late stages of stellar evolution
alternative label: Late-stage stellar evolution
broader: Stellar astronomy
narrower: Supernovae
narrower: Compact objects
narrower: Degenerate matter
narrower: Ejecta
related: Supernova dynamics
contributor: AAS Frey.Katie
narrower: AM Herculis stars
narrower: Novae
narrower: Nova-like variable stars

Symbiotic novae
modified: 2018-09-13T15:28:10.000Z
type: Concept
broader: Novae
broader: Symbiotic binary stars
contributor: AAS Frey.Katie

BY Draconis stars
modified: 2018-09-13T16:34:41.000Z
type: Concept
contributor: AAS Frey.Katie Admin
broader: Eruptive variable stars

Eruptive variable stars
modified: 2018-09-14T15:32:49.000Z
type: Concept
alternative label: Eruptive variables
broader: Intrinsic variable stars
narrower: Flare stars
contributor: AAS Frey.Katie Admin
narrower: BY Draconis stars
narrower: Gamma Cassiopeiae stars
narrower: Luminous blue variable stars

UU Herculis stars
modified: 2018-09-13T16:48:06.000Z
type: Concept
broader: F supergiant stars
contributor: AAS Frey.Katie Admin
broader: Double-mode variable stars
broader: SRd variable stars

Multi-periodic pulsation
modified: 2018-09-13T16:49:20.000Z
type: Concept
alternative label: Multiperiodic pulsation
broader: Stellar pulsations
narrower: Double-mode pulsation
contributor: AAS Frey.Katie Admin
related: Multi-periodic variable stars

Multi-periodic variable stars
contributor: AAS Frey.Katie
type: Concept
alternative label: Multiperiodic variable stars
broader: Periodic variable stars
broader: Pulsating variable stars
narrower: PG 1159 stars
narrower: Beta Cephei variable stars
narrower: SX Phoenicis variable stars
narrower: ZZ Ceti stars
narrower: Delta Scuti variable stars
narrower: Double-mode variable stars
related: Multi-periodic pulsation
narrower: Double periodic variable stars
narrower: OGLE small amplitude red giant stars
modified: 2019-12-03T16:53:37.398Z

Exoplanet structure
contributor: AAS Frey.Katie
type: Concept
broader: Exoplanet astronomy
narrower: Exoplanet atmospheres
narrower: Exoplanet rings
narrower: Exoplanet plate tectonics
related: Planetary structure
narrower: Exoplanet surfaces
modified: 2019-12-02T19:12:55.520Z

Herbig-Haro objects
modified: 2018-09-13T16:54:53.000Z
type: Concept
alternative label: HH objects
alternative label: HH-object
alternative label: Herbig Haro objects
alternative label: Herbig–Haro object
broader: Intrinsic variable stars
related: Emission nebulae
related: Infrared sources
contributor: AAS Frey.Katie Admin
broader: Young stellar objects

Yellow straggler stars
modified: 2018-09-13T16:58:11.000Z
type: Concept
alternative label: Yellow-straggler stars
broader: Stellar evolutionary types
related: Blue straggler stars
alternative label: Yellow stragglers
contributor: AAS Frey.Katie Admin

B subdwarf stars
modified: 2018-09-13T17:04:16.000Z
broader: Subdwarf stars
type: Concept
alternative label: B subdwarfs
broader: B stars
alternative label: B-type subdwarf stars
alternative label: B-type subdwarfs
contributor: AAS Frey.Katie Admin

O subdwarf stars
modified: 2018-09-13T17:05:00.000Z
broader: Subdwarf stars
type: Concept
alternative label: O subdwarfs
broader: O stars
alternative label: O-type subdwarf stars
alternative label: O-type subdwarfs
contributor: AAS Frey.Katie Admin

B dwarf stars
modified: 2018-09-13T17:05:37.000Z
type: Concept
alternative label: B dwarfs
broader: B stars
alternative label: B-type dwarf stars
alternative label: B-type dwarfs
contributor: AAS Frey.Katie Admin
broader: Dwarf stars

O dwarf stars
modified: 2018-09-13T17:05:48.000Z
broader: Dwarf stars
type: Concept
alternative label: O dwarfs
broader: O stars
alternative label: O-type dwarfs
alternative label: O-type dwarf stars
alternative label: O-type main sequence stars
contributor: AAS Frey.Katie Admin

Stellar types
modified: 2018-09-13T17:09:56.000Z
type: Concept
alternative label: Stars
broader: Stellar astronomy
narrower: Multiple stars
narrower: Novae
narrower: Protostars
narrower: Supernovae
narrower: Variable stars
narrower: Chemically peculiar stars
narrower: Emission line stars
contributor: AAS Frey.Katie Admin
narrower: Early-type stars
narrower: Intermediate-type stars
narrower: Late-type stars
narrower: Low mass stars
narrower: Stellar evolutionary types
narrower: Massive stars
narrower: Stellar spectral types
narrower: Field stars
narrower: Solar analogs

R stars
modified: 2018-09-13T17:15:45.000Z
type: Concept
alternative label: Class R stars
alternative label: R-type stars
broader: Carbon stars
broader: Giant stars
broader: Late-type stars
contributor: AAS Frey.Katie Admin
broader: Stellar spectral types

Interstellar cyclotron emission
modified: 2018-09-13T19:12:25.000Z
type: Concept
broader: Interstellar emissions
contributor: AAS Frey.Katie
alternative label: Interstellar cyclotron radiation

Circular orbits
modified: 2018-09-13T19:36:15.000Z
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
alternative label: Circular orbit

AM Herculis stars
modified: 2018-09-13T20:20:08.000Z
type: Concept
alternative label: Polars
broader: Cataclysmic variable stars
related: DQ Herculis stars
broader: Stellar remnants
contributor: AAS Frey.Katie Admin

Me stars
modified: 2018-09-13T20:23:44.000Z
type: Concept
broader: Emission line stars
broader: M stars
related: Mira variable stars
alternative label: Me-type stars
contributor: AAS Frey.Katie Admin
narrower: Me variable stars

Transit photometry
modified: 2018-09-14T14:57:41.000Z
type: Concept
broader: Exoplanet detection methods
contributor: AAS Frey.Katie Admin
broader: Photometry

HST photometry
modified: 2018-09-14T15:04:11.000Z
type: Concept
alternative label: Hubble photometry
broader: Broad band photometry
contributor: AAS Frey.Katie Admin
alternative label: Hubble Space Telescope photometry
alternative label: HST Fnnn(LMNW) photometry

E layer
modified: 2018-09-14T15:25:23.000Z
type: Concept
alternative label: Kennelly–Heaviside layer
broader: Earth ionosphere
contributor: AAS Frey.Katie Admin

Astrophysical masers
modified: 2018-09-14T15:29:50.000Z
type: Concept
alternative label: Super-radiant emission
alternative label: Superradiant emission
broader: Extragalactic astronomy
broader: Interstellar medium
narrower: Megamasers
narrower: Silicon monoxide masers
narrower: Water masers
narrower: Hydroxyl masers
related: Molecular clouds
related: Planetary atmospheres
related: Stellar atmospheres
related: Comets
contributor: AAS Frey.Katie Admin

Lyman-alpha forest clouds
modified: 2018-09-14T15:35:53.000Z
type: Concept
broader: Intergalactic clouds
contributor: AAS Frey.Katie Admin
alternative label: Lyman alpha forest clouds

Galaxy accretion disks
modified: 2018-09-14T16:44:42.000Z
type: Concept
broader: Galaxy physics
alternative label: Galaxy accretion discs
related: Galaxy accretion
contributor: AAS Frey.Katie Admin
alternative label: Galactic accretion disks

Massive stars
modified: 2020-11-02T16:42:11.118Z
type: Concept
narrower: High mass x-ray binary stars
contributor: AAS Frey.Katie Admin
alternative label: High mass stars
alternative label: High-mass stars
broader: Stellar types
definition: A star whose mass is larger than approximately 10 solar masses. The spectral types of massive stars range from about B3 (B star) to O2 (O star) and include Wolf-Rayet stars as well as Luminous Blue Variables. Massive stars are very rare; for each star of 20 solar masses there are some 100,000 stars of 1 solar mass. Despite this rarity, they play a key role in astrophysics. They are major sites of nucleosynthesis beyond oxygen and, therefore, are mainly responsible for the chemical evolution of galaxies. Due to their high ultraviolet flux and powerful stellar winds, they bring about interesting phenomena in the interstellar medium, like H II regions, turbulence, shocks, bubbles, and so on. Massive stars are progenitors of supernovae (type Ia, type Ic and type II), neutron stars, and black holes. The formation processes of massive stars is still an unresolved problem. For massive stars the accretion time scale is larger than the Kelvin-Helmholtz time scale. This means that massive stars reach the main sequence while accretion is still going on.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:42:28.333Z
modified: 2020-11-02T16:42:28.357Z

Stellar radii
modified: 2018-09-14T19:08:58.000Z
type: Concept
alternative label: Stellar radius
broader: Stellar properties
contributor: AAS Frey.Katie Admin
related: Solar radius

Solar filaments
modified: 2018-09-14T19:33:25.000Z
type: Concept
alternative label: Solar flocculi
alternative label: Solar flocculus
related: Solar prominences
scope note: A solar prominence, but seen on the disk.
broader: Solar activity
narrower: Solar active region filaments
narrower: Solar filament eruptions
narrower: Quiescent solar prominence
contributor: AAS Frey.Katie Admin

Cosmological models
modified: 2018-09-17T15:02:21.000Z
type: Concept
alternative label: Classical tests of cosmology
broader: Cosmology
narrower: Newtonian cosmology
narrower: Open universe
narrower: Oscillating universe
narrower: Closed universe
narrower: de Sitter universe
narrower: Dirac cosmology
narrower: Einstein universe
narrower: Expanding universe
narrower: Friedmann universe
narrower: Gödel universe
narrower: Inflationary universe
narrower: Lemaitre universe
contributor: AAS Frey.Katie Admin
narrower: Geocentric model
narrower: Heliocentric model

Astronomical models
modified: 2018-09-17T15:02:21.000Z
type: Concept
broader: Analytical mathematics
narrower: Mass-to-light ratio
narrower: Oort constants
narrower: Star counts
narrower: Burkert profile
narrower: Gas-to-dust ratio
contributor: AAS Frey.Katie Admin

Nuclear astrophysics
modified: 2018-09-20T14:56:27.000Z
type: Concept
broader: Astrophysical processes
narrower: Astrophysical explosive burning
narrower: Neutrino oscillations
narrower: Neutron stars
narrower: Nucleosynthesis
narrower: Solar neutrinos
contributor: AAS Frey.Katie Admin
related: Nuclear physics
narrower: Nuclear fission
narrower: Nuclear fusion

Interstellar dust processes
modified: 2018-09-20T15:03:06.000Z
type: Concept
alternative label: Interstellar dust grain processes
alternative label: Interstellar grain processes
broader: Astrophysical dust processes
related: Interstellar dust
contributor: AAS Frey.Katie Admin
related: Solid matter physics

Mass spectrometers
modified: 2018-09-20T15:33:26.000Z
type: Concept
broader: Spectrometers
contributor: AAS Frey.Katie Admin
related: Mass spectrometry

Cosmic abundances
modified: 2018-09-20T15:42:55.000Z
type: Concept
broader: Chemical abundances
related: Cosmochemistry
contributor: AAS Frey.Katie Admin

Interplanetary shocks
modified: 2018-09-20T16:50:23.000Z
type: Concept
broader: Interplanetary physics
contributor: AAS Frey.Katie Admin
broader: Shocks

Planetary bow shocks
modified: 2018-09-20T16:50:30.000Z
type: Concept
broader: Interplanetary physics
contributor: AAS Frey.Katie Admin
broader: Shocks

Stellar bow shocks
modified: 2018-09-20T16:50:44.000Z
type: Concept
alternative label: Solar bow shock
broader: Heliosphere
contributor: AAS Frey.Katie Admin
broader: Shocks

Plasma astrophysics
modified: 2018-09-20T16:51:17.000Z
type: Concept
broader: Cosmology
broader: High energy astrophysics
narrower: Space plasmas
narrower: Cosmic electrodynamics
contributor: AAS Frey.Katie Admin
related: Plasma physics
narrower: Shocks
narrower: Magnetohydrodynamics

Zeeman-Doppler imaging
modified: 2018-09-20T17:31:35.000Z
type: Concept
alternative label: ZDI
alternative label: Zeeman Doppler imaging
broader: Doppler imaging
contributor: AAS Frey.Katie Admin

L subdwarfs
modified: 2018-09-20T21:02:44.000Z
contributor: AAS Frey.Katie Admin
alternative label: L subdwarf stars
type: Concept
broader: Brown dwarfs
alternative label: L-type brown subdwarfs
alternative label: L brown subdwarfs

T subdwarfs
modified: 2018-09-20T21:02:56.000Z
broader: Subdwarf stars
type: Concept
broader: Brown dwarfs
alternative label: T-type brown subdwarfs
alternative label: T brown subdwarfs
contributor: AAS Frey.Katie Admin
alternative label: T subdwarf stars

Ultraviolet sources
modified: 2018-09-20T21:22:32.000Z
type: Concept
alternative label: UV sources
alternative label: Ultraviolet objects
broader: Astronomical radiation sources
narrower: Ultraviolet transient sources
contributor: AAS Frey.Katie Admin
related: Ultraviolet astronomy

Infrared sources
modified: 2018-09-20T21:22:53.000Z
related: Infrared astronomy
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: IR sources
broader: Astronomical radiation sources
related: OH/IR stars
related: Cocoon stars
related: Extreme carbon stars
related: FU Orionis stars
related: Herbig-Haro objects
related: Infrared galaxies

Bekenstein-Hawking entropy
modified: 2018-09-21T14:07:54.000Z
type: Concept
broader: Black hole physics
contributor: AAS Frey.Katie Admin

Astrophysical dust processes
modified: 2019-03-26T18:21:50.000Z
type: Concept
broader: Cosmology
narrower: Interstellar dust processes
related: Solid matter physics
contributor: AAS Frey.Katie
related: Intergalactic medium

Polar orbit
modified: 2020-11-17T19:47:11.841Z
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
definition: A spacecraft orbit that passes over, or close to, the geographic poles of the Earth or some other solar system object.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:47:21.689Z
modified: 2020-11-17T19:47:21.721Z

DQ Herculis stars
alternative label: Intermediate polar stars
type: Concept
alternative label: Intermediate polars
related: AM Herculis stars
broader: Novae
related: AM Canum Venaticorum stars
definition: A type of cataclysmic variable binary star system with a white dwarf and a cool main-sequence secondary star.
contributor: AAS Frey.Katie
modified: 2020-11-03T20:19:43.934Z
modified: 2020-11-03T20:20:23.152Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T20:20:23.119Z
  comment: Wikipedia

Absolute magnitude
type: Concept
broader: Magnitude
definition: The magnitude a star would have if it were at a distance of 10 parsecs in a void space, without interstellar absorption. The absolute magnitude is usually deduced from the visual magnitude, measured through a V filter (UBV system), when it is written as M_V. If it is defined for another wavelength, it gets another index (U, B, etc). If the radiation on all wavelengths is included, it becomes absolute bolometric magnitude, M_bol. The Sun has the absolute magnitude +4.8. Most of the stars have absolute magnitudes ranging between -9 (supergiants) and +19 (red dwarfs).
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:48:12.505Z
modified: 2020-11-03T17:44:54.488Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T17:44:54.457Z

Astrophysical explosive burning
type: Concept
alternative label: Explosive astronomical burning
alternative label: Explosive astrophysical burning
broader: Nuclear astrophysics

Main sequence stars
type: Concept
narrower: Zero-age main sequence stars
broader: Stellar evolutionary types
alternative label: Stars on the main sequence
related: Main sequence
related: Dwarf stars
related: Beta Cephei variable stars
contributor: AAS Frey.Katie
modified: 2019-12-03T18:25:28.028Z

Major axis
type: Concept
broader: Elliptical orbits
contributor: AAS Frey.Katie
modified: 2020-11-10T19:12:07.883Z
definition: The greatest diameter of an ellipse; it passes through the two foci.
modified: 2020-11-10T19:12:20.939Z
editorial note: Definition Provenance
  created: 2020-11-10T19:12:20.910Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Maksutov telescopes
type: Concept
broader: Catadioptric telescopes

Manganese stars
type: Concept
broader: Chemically peculiar stars
broader: Ap stars
broader: Heavy metal stars

Mantle
type: Concept
broader: Planetary structure
contributor: AAS Frey.Katie
modified: 2020-11-10T19:13:31.514Z
definition: A major subdivision of a planet's internal structure, located beneath the planet's crust and above the central core.
editorial note: Definition Provenance
  created: 2020-11-10T19:13:41.347Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-10T19:13:41.375Z

Markarian galaxies
type: Concept
broader: Active galaxies
broader: Emission line galaxies

Mars
type: Concept
broader: Solar system terrestrial planets
related: Martian satellites
definition: Fourth planet from Sun and the seventh largest. Mass 6.42 x 10^26 g (0.11 Earth's); radius 3397 km. Mean distance from Sun 1.52 AU. Sidereal period 687 days; synodic period 779.9 days. Surface temperature 248 K., rotational period 24h 37m 22.66s. Obliquity 23°59'. Atmosphere more than 90% CO_2, traces of O_2, CO, H_{2}O. Two tiny satellites (Phobos and Deimos), both of which are locked in synchronous rotation with Mars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:16:58.160Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:15:28.737Z
modified: 2020-11-10T19:15:28.771Z
contributor: AAS Frey.Katie

Mars trojans
type: Concept
broader: Trojan asteroids
contributor: AAS Frey.Katie
definition: The family of asteroids located at either of the stable Lagrangian points (L4 or L5) of the orbit of Mars.
modified: 2020-11-10T19:17:35.491Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:17:45.061Z
modified: 2020-11-10T19:17:45.090Z

Martian satellites
type: Concept
alternative label: Deimos
alternative label: Martian moons
alternative label: Moons of Mars
alternative label: Phobos
broader: Natural satellites (Solar system)
related: Mars
example: Deimos
contributor: AAS Frey.Katie Admin
example: Phobos
modified: 2020-12-09T15:23:39.718Z

Mascon
type: Concept
alternative label: Mass concentration
broader: Gravity anomaly
contributor: AAS Frey.Katie
definition: A region on the surface of the Moon where the gravitational attraction is slightly higher than normal due to the presence of dense rock.
modified: 2020-11-10T19:18:21.005Z
editorial note: Definition Provenance
  created: 2020-11-10T19:18:30.130Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-10T19:18:30.157Z

Mass-to-light ratio
type: Concept
broader: Astronomical models

Mass ratio
type: Concept
alternative label: Mass-ratio
broader: Three-body problem

Matter density
type: Concept
broader: Density parameters

Maunder minimum
type: Concept
alternative label: Prolonged sunspot minimum
broader: Sunspots
contributor: AAS Frey.Katie Admin
definition: A period from about 1645 to 1715 when the number of sunspots was unusually low. This solar activity minimum is attested also through the increased content of carbon-14 in tree rings in that period. The reason is that the cosmic rays which produce carbon-14 reach the Earth in a greater number when there is weak solar activity. The Maunder minimum occurred during a period of cooling of the Earth, called the Little Ice Age. The Maunder minimum is one of a number of periods of low solar activity, including the Dalton minimum, the Sporer minimum, the Wolf minimum, and the Oort minimum.
modified: 2020-11-24T16:47:12.177Z
modified: 2020-11-10T19:21:02.629Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:21:02.595Z

Maximal Kerr black holes
type: Concept
broader: Kerr black holes

Mean anomaly
type: Concept
broader: Orbital anomalies
contributor: AAS Frey.Katie
definition: The angle between the periapsis of an orbit and the position of a hypothetical body that orbits in the same period as the real one but at a constant mean angular velocity.
modified: 2020-11-10T19:21:32.851Z
modified: 2020-11-10T19:21:54.127Z
editorial note: Definition Provenance
  created: 2020-11-10T19:21:54.097Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Astrophysical magnetism
type: Concept
broader: Astrophysical processes
narrower: Cosmic magnetic fields theory
narrower: Emerging flux tubes
narrower: Magnetic fields

Mean matter density
type: Concept
alternative label: Mean density
alternative label: Mean mass density
broader: Large-scale structure of the universe

Medium band photometry
type: Concept
broader: Photometric systems
narrower: Strömgren photometry
narrower: Vilnius photometry
narrower: Walraven photometry
narrower: DDO photometry
narrower: Geneva photometry
related: Infrared photometry

Megalithic astronomy
type: Concept
broader: Archaeoastronomy
modified: 2022-06-24T17:47:42.113Z
related: Stone circles
contributor: AAS Frey.Katie Admin

Megamasers
type: Concept
broader: Astrophysical masers

Mercury (planet)
type: Concept
broader: Solar system terrestrial planets
contributor: AAS Frey.Katie
alternative label: Mercury
definition: The closest planet to the Sun and one of five planets visible with the naked eye. The greatest elongation of Mercury is about 28°, making it visible at most about 112 minutes after sunset or before sunrise. It lies at a mean distance of about 0.39 astronomical units from the Sun. Mercury is just 4,879 km in diameter, about 2.6 times smaller than the Earth. Its orbital period is 87.97 Earth days. Mercury has a high density, 5.4 g cm^-3, with only the Earth having a higher density among the planets. This is largely due to Mercury being composed mainly of heavy metals and rock. One solar day on Mercury lasts the equivalent of 176 Earth days while the sidereal day (the time for 1 rotation in relation to a fixed point) lasts 59 Earth days. Mercury is nearly tidally locked to the Sun and over time this has slowed the rotation of the planet to almost match its orbit around the Sun. Mercury also has the highest orbital eccentricity of all the planets with its distance from the Sun ranging from 46 to 70 million km. Mercury has just 38% the gravity of Earth, this is too little to maintain an atmosphere against solar winds, which blow it away. The surface of Mercury which faces the Sun has temperatures of up to 427°C, whilst on the alternate side this can be as low as -173°C. Mercury's core has more iron than any other planet in the solar system. This has to do with its formation and early life. If the planet formed quickly, increasing temperatures of the evolving Sun could have vaporized much of the existing surface, leaving only a thin shell.
modified: 2020-11-10T19:22:32.883Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T19:22:43.765Z
  creator: AAS Frey.Katie
modified: 2020-11-10T19:22:43.791Z

Mercury-manganese stars
type: Concept
alternative label: Mercury manganese stars
broader: B stars
broader: Chemically peculiar stars
broader: Magnetic stars
contributor: AAS Frey.Katie
definition: Chemically peculiar stars of late B-types. The most distinctive features of Mercury-manganese stars are extreme atmospheric overabundance of Hg (up to 5 dex) and of Mn (up to 3 dex). The origin of abundance anomalies observed in late B-type stars with HgMn peculiarity is still poorly understood. More than two thirds of the HgMn stars are known to belong to spectroscopic binaries with a preference of orbital periods ranging from 3 to 20 days.
modified: 2020-11-10T19:23:39.864Z
modified: 2020-11-10T19:23:49.915Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T19:23:49.885Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Meridian
type: Concept
broader: Horizontal coordinate system
contributor: AAS Frey.Katie
definition: An imaginary great circle on the celestial sphere that passes through its poles and the observer's zenith.
modified: 2020-11-10T19:24:23.072Z
editorial note: Definition Provenance
  created: 2020-11-10T19:24:32.327Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T19:24:32.358Z

Meridian circles
type: Concept
alternative label: Transit circles
broader: Telescopes
broader: Transit instruments
contributor: AAS Frey.Katie Admin
modified: 2021-03-30T14:16:13.640Z
definition: A telescope with a graduated vertical scale, used to measure the declinations of heavenly bodies and sometimes to determine the time of meridian transits.
modified: 2020-11-10T19:25:07.977Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T19:25:07.948Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie

Mesogranulation
type: Concept
broader: Solar granulation

Mesopause
type: Concept
broader: Earth atmosphere

Mesosphere
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: The layer of the atmosphere located between the stratosphere and the ionosphere, where temperature drops rapidly with increasing height. It extends between 17 to 80 kilometers above the Earth's surface.
modified: 2020-11-10T19:27:09.377Z
editorial note: Definition Provenance
  created: 2020-11-10T19:27:18.609Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T19:27:18.639Z

Metallicity
type: Concept
broader: Chemical abundances
alternative label: Metal abundances
contributor: AAS Frey.Katie
definition: In a star, nebula, or galaxy, the proportion of the material that is made up of metals, that is elements heavier than helium. It is generally denoted by Z. The term 'metallicity' is a misnomer used in astrophysics. In practice, the metallicity of stars is usually expressed by the number ratio of iron atoms to hydrogen atoms per unit volume, with respect to the solar values: [Fe/H] = log10(NFe/NH)star - log10(NFe/NH)Sun, where NFe and NH are the numbers of iron and hydrogen atoms per unit volume. In fact it is taken to be equal to the iron abundance with respect to the solar value. The solar logarithmic iron abundance is 7.50 ± 0.04, with respect to that of hydrogen which, by convention, is 12.00. Stellar metallicity is often expressed in mass fraction. Nebular metallicity is often defined as the relative abundance of oxygen: (NO/NH)neb/(NO/NH)Sun, where N_O and N_H represent the numbers of oxygen and hydrogen atoms per unit volume.
modified: 2020-11-10T19:28:29.949Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T19:28:44.215Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T19:28:44.248Z

Metal line absorbers
type: Concept
broader: Intergalactic clouds

Meteor radiants
type: Concept
broader: Meteor showers

Meteor showers
type: Concept
narrower: Meteor radiants
broader: Meteors
modified: 2020-11-09T22:12:30.237Z
definition: An increased number of meteors all appearing to diverge from the direction of a single point, called radiant. Meteor showers occur annually on the same dates, when the Earth crosses through a meteoroid stream. Meteor showers are named after the constellation in which the radiant is located. For example, the Perseids's radiant lies near the top of the constellation Perseus. Most meteor showers are caused by comets. As a comet orbits the Sun it sheds an icy, dusty debris stream along its orbit. When the Earth's orbit intersects the dust trail, more meteors are seen as the cometary debris encounters our planet's atmosphere. In the case of the Geminids and Quadrantids, those meteor showers come from the debris scattered by orbiting asteroids. Typical meteor showers show 15 to 100 meteors per hour at their peak. On very rare occasions, during a meteor storm, thousands of meteors fall per hour. Prominent meteor showers are: Quadrantids, Lyrids, Eta Aquariids, Delta Aquariids, Perseids, Orionids, Taurids, Leonids, Geminids, Ursids, Alpha Capricornids.
contributor: AAS Frey.Katie Admin
narrower: Zenith hourly rate
editorial note: Definition Provenance
  created: 2020-11-03T18:35:45.078Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:35:45.108Z

Meteor streams
type: Concept
broader: Meteors
definition: The meteoroids distributed all along an orbit and diffused somewhat around it.
contributor: AAS Frey.Katie Admin
alternative label: Meteoroid stream
modified: 2020-11-03T18:51:26.052Z
modified: 2020-11-03T18:51:39.675Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:51:39.646Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Meteor trails
type: Concept
alternative label: Trail of meteors
alternative label: Trails of meteors
broader: Meteors

Meteorite composition
type: Concept
alternative label: Composition of meteorites
broader: Meteorites
contributor: AAS Frey.Katie
modified: 2019-12-11T19:01:59.156Z

Meteorites
type: Concept
broader: Meteoroids
narrower: Micrometeorites
narrower: Ataxites
narrower: Achondrites
narrower: Tektites
narrower: Aerolites
narrower: Chondrites
narrower: Iron meteorites
related: Meteors
related: Impact phenomena
narrower: Meteorite composition
definition: An object of extraterrestrial origin that survives entry through the atmosphere to reach the Earth's surface. Meteors become meteorites if they reach the ground.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T18:54:42.711Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:54:55.236Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:54:55.262Z

Meteoroid dust clouds
type: Concept
alternative label: Meteoric clouds
alternative label: Meteoric dust
broader: Interplanetary dust
alternative label: Meteoroid dust
modified: 2020-12-17T16:21:54.641Z
contributor: AAS Frey.Katie Admin

Astrophysical processes
type: Concept
narrower: Astrophysical magnetism
narrower: Nuclear astrophysics
narrower: Relativity
narrower: Gravitation
top concept of: The Unified Astronomy Thesaurus
contributor: AAS Frey.Katie
modified: 2022-03-29T17:21:25.592Z

Meteoroids
type: Concept
broader: Solar system
narrower: Meteorites
narrower: Meteors
narrower: Micrometeoroids
definition: A solid object in interplanetary space before it reaches the Earth's atmosphere. Meteoroids are of silicate and/or metallic matter having a size from tiniest grains up to that of the smallest asteroids.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T18:50:36.164Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:50:49.326Z
modified: 2020-11-03T18:50:49.351Z

Meteors
type: Concept
broader: Meteoroids
narrower: Meteor streams
narrower: Meteor trails
narrower: Fireballs
related: Meteorites
narrower: Meteor showers
definition: A streak of light caused when a meteoroid enters Earth's atmosphere and becomes incandescent, mostly from friction with the air at high speed. Meteors are also referred to as shooting stars. Very bright meteors are called fireball or bolide. Most of visible meteors arise from particles ranging in size from about that of a small pebble down to a grain of sand, and generally weigh less than 1-2 grams. The brilliant flash of light from a meteor is mainly caused by the meteoroid's high level of kinetic energy as it collides with the atmosphere at high speeds (11-72 km/s). The increase in the number of meteors visible toward the end of the night results from the fact that the Earth rotates about its axis in the same direction as it orbits the Sun. This means that the leading edge (morning side) of the Earth encounters more meteoroids than the trailing edge (evening side). In general, 2 to 3 times as many meteors can be seen in the hour or so just before morning twilight, than can be seen in the early evening. Moreover, the numbers of random, or sporadic, meteors vary from season to season, due to the tilt of the Earth on its axis and other factors.
modified: 2020-11-03T18:49:51.264Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:50:05.735Z
modified: 2020-11-03T18:50:05.771Z

Methane
type: Concept
alternative label: C h4
alternative label: C h_4
broader: Greenhouse gases
definition: A colorless, odorless, inflammable gas of formula CH4; the simplest hydrocarbon.
modified: 2020-11-24T17:36:48.209Z
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T19:31:51.850Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T19:31:51.884Z

Astronomical methods
type: Concept
broader: Observational astronomy
narrower: Neutrino astronomy
narrower: Observational cosmology
narrower: Radar astronomy
narrower: Radio astronomy
narrower: Ultraviolet astronomy
narrower: Optical astronomy
narrower: X-ray astronomy
narrower: Computational astronomy
narrower: Cosmic ray astronomy
narrower: Amateur astronomy
narrower: Gamma-ray astronomy
narrower: Gravitational wave astronomy
narrower: Ground-based astronomy
narrower: Infrared astronomy
narrower: Astrophotography
alternative label: Observation methods
alternative label: Methods
narrower: Time domain astronomy
modified: 2020-11-09T22:08:25.853Z
contributor: AAS Frey.Katie Admin

Michelson interferometers
type: Concept
broader: Interferometers
related: Michelson interferometry

Michelson interferometry
type: Concept
broader: Optical phase shifting interferometry
related: Michelson interferometers

Microgravity
type: Concept
broader: Space research
contributor: AAS Frey.Katie
definition: The state or condition where the force of gravity is very weak, e.g. the weightlessness experienced inside an orbiting spacecraft.
modified: 2020-11-10T19:33:58.172Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:34:08.602Z
modified: 2020-11-10T19:34:08.629Z

Micrometeorites
type: Concept
broader: Meteorites
definition: A small grain sized meteorite which can only be positively identified under the microscope.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T18:53:32.725Z
modified: 2020-11-03T18:53:46.901Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:53:46.877Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Micrometeoroids
type: Concept
broader: Meteoroids

Astrophysicists
type: Concept
broader: Astronomical research
definition: A scientist who studies astrophysics.
modified: 2020-11-04T22:11:45.408Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T22:12:01.922Z
modified: 2020-11-04T22:12:01.954Z

Milky Way Galaxy
type: Concept
alternative label: Milky Way
alternative label: Our galaxy
alternative label: The Galaxy
broader: Spiral galaxies
broader: Local Group
related: Milky Way Galaxy physics
related: Oort constants
related: Magellanic Clouds
contributor: AAS Frey.Katie Admin
definition: A spiral galaxy, of which the solar system is a small part. It is the second largest in our Local Group of galaxies. The Milky Way is a disk-shaped system, with a diameter of between 80,000 and 100,000 light-years and a thickness of about 2,000 light-years, containing more than 10^11 stars. The stars are divided into two main categories, Population II stars and Population I stars. The core, or nucleus, of the Galaxy is surrounded by an ellipsoidal central bulge that measures some 15,000 light-years in diameter and about 6,000 light-years in the direction perpendicular to the plane of the disk. Surrounding the bulge and extending in a near spherical distribution above and below the Galactic plane is the Galactic halo. The halo contains about 200 globular clusters and an extremely thinly scattered population of individual stars. The Sun is located just over half way out from the center to the edge of the disk at a distance of about 25,000 light-years. In common with other stars, the Sun revolves around the Galactic Center. Its orbital velocity is about 220 km s^-1 and its orbital period is about 225 million years. Overall, the Galaxy exhibits differential rotation, that is stars and gas clouds closer to the center have shorter orbital periods than those that are located further out. The spiral arms of the Milky Way lie within its disk, where bright young stars, H II regions, and molecular clouds of gas and dust are concentrated into curved 'arms' that appear to radiate from the central bulge in a spiral pattern. The Galaxy's spiral pattern consists of several major arms and a number of shorter segments, one of which, the Orion arm, contains the Sun and the Orion star-forming region. Near-infrared observations have shown that the stars in the central bulge are arranged in an elongated galactic bar, about twice as long as it is wide, that is seen nearly end on from the present location of the solar system. The exact center, or nucleus, of the Galaxy coincides with a str…
modified: 2020-11-24T19:35:57.559Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:57:42.353Z
modified: 2020-11-03T18:57:42.388Z

Milky Way Galaxy fountains
type: Concept
broader: Milky Way Galaxy physics
related: Galaxy fountains

Milky Way Galaxy physics
type: Concept
broader: Galaxy physics
narrower: Milky Way dark matter halo
narrower: Milky Way disk
narrower: Milky Way dynamics
narrower: Milky Way evolution
narrower: Milky Way formation
narrower: Milky Way Galaxy fountains
narrower: Milky Way magnetic fields
narrower: Milky Way mass
narrower: Milky Way rotation
narrower: Milky Way stellar halo
narrower: Solar neighborhood
narrower: Galactic anticenter
narrower: Galactic center
narrower: Galactic winds
narrower: Gould Belt
related: Milky Way Galaxy
narrower: Galactic abundances
narrower: Galactic bulge
narrower: Galactic archaeology
contributor: AAS Frey.Katie Admin
modified: 2020-11-25T18:51:42.117Z
narrower: Galactic bar

Astrosphere interstellar medium interactions
type: Concept
alternative label: Astrosphere-interstellar medium interactions
alternative label: Astrosphere/interstellar medium interactions
broader: Stellar phenomena
related: Heliosphere

Millimeter astronomy
type: Concept
broader: Radio astronomy
preferred label: Millimetre astronomy
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:42:20.353Z

Millisecond pulsars
type: Concept
broader: Pulsars

Mini Neptunes
type: Concept
broader: Exoplanets

Minor axis
type: Concept
broader: Elliptical orbits
contributor: AAS Frey.Katie
definition: The axis of an ellipse that is perpendicular to the major axis at a point equidistant from the foci.
modified: 2020-11-10T19:35:47.868Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:35:58.614Z
modified: 2020-11-10T19:35:58.642Z

Mira variable stars
type: Concept
alternative label: Mira variables
alternative label: Miras
alternative label: Omicron ceti stars
alternative label: Zeta aurigae stars
broader: Pulsating variable stars
broader: Emission line stars
contributor: AAS Frey.Katie Admin
broader: Late-type giant stars
broader: Long period variable stars
related: Me stars
modified: 2020-12-16T15:43:34.765Z

Missing mass
type: Concept
broader: Intergalactic medium
contributor: AAS Frey.Katie
definition: The unseen mass whose gravitational influence is needed to account for the way galaxies rotate, and also to bind clusters of galaxies together. It is thought to consist, in part, of giant halos of dark matter that surround the visible portions of galaxies, and similar material that invisibly occupies the intergalactic voids.
modified: 2020-11-10T19:36:44.485Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:36:54.921Z
modified: 2020-11-10T19:36:54.947Z

Modified Newtonian dynamics
type: Concept
alternative label: M o n d
broader: Non-standard theories of gravity

Astrospheres
type: Concept
broader: Stellar-interstellar interactions

Radical-radical recombination
type: Concept
contributor: AAS Frey.Katie Admin
broader: Recombination
broader: Molecular reactions
modified: 2022-06-11T22:56:51.935Z

Molecular clouds
type: Concept
alternative label: H2 clouds
broader: Interstellar clouds
narrower: Photodissociation regions
narrower: Collapsing clouds
narrower: Diffuse molecular clouds
narrower: Giant molecular clouds
narrower: Infrared dark clouds
related: Astrophysical masers

Molecular gas
type: Concept
broader: Interstellar phases

Moving cluster parallax
type: Concept
alternative label: Cluster parallax
broader: Parallax
related: Moving clusters

Moving clusters
type: Concept
related: Moving cluster parallax
broader: Star clusters
definition: A group of stars dynamically associated so that they have a common motion with respect to the local standard of rest.
modified: 2020-11-04T16:36:22.490Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T16:36:36.687Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T16:36:36.661Z

Multi-color photometry
type: Concept
alternative label: Multicolor photometry
broader: Photometric systems
preferred label: Multi-colour photometry
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:20:45.191Z

Asymptotic giant branch
type: Concept
alternative label: AGB
broader: Hertzsprung Russell diagram
contributor: AAS Frey.Katie Admin
related: Asymptotic giant branch stars
definition: A region of the Hertzsprung-Russell diagram populated by evolving low-mass to intermediate-mass stars. These stars have an electron degenerate core of carbon and oxygen surrounded by two burning shells of helium and hydrogen. The H and He-burning shells are activated alternately in the deep layers of the star. An extended and tenuous convection envelope, having a radius of 10^4 - 10^5 times the size of the core, lies above these shells. The loosely bound envelope is gradually eroded by the strong stellar wind, which forms a dusty circumstellar envelope out to several hundreds of stellar radii. The convective envelope, stellar atmosphere, and circumstellar envelope have a rich and changing chemical composition provided by nucleosynthesis processes in the burning shells in the deep interior.
modified: 2020-11-05T18:59:52.888Z
editorial note: Definition Provenance
  created: 2020-11-09T21:28:43.331Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T21:28:43.360Z

Multiple stars
type: Concept
broader: Stellar types
narrower: Binary stars
narrower: Trinary stars

N-body problem
type: Concept
alternative label: N body problem
broader: Celestial mechanics
narrower: Few-body systems
related: N-body simulations
contributor: AAS Frey.Katie
definition: The mathematical problem of studying the behavior (e.g., velocities, positions) of any number of objects moving under their mutual gravitational attraction for any time in the past or future.
modified: 2020-11-10T19:37:33.981Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:37:44.193Z
modified: 2020-11-10T19:37:44.224Z

N galaxies
type: Concept
broader: Compact galaxies

Nadir
type: Concept
broader: Horizontal coordinate system
contributor: AAS Frey.Katie
definition: The point on the celestial sphere blocked from view by Earth and diametrically opposite to the zenith.
modified: 2020-11-10T19:38:08.834Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:38:21.928Z
modified: 2020-11-10T19:38:21.956Z

Naked singularities
type: Concept
broader: Gravitational singularities

Narrow band photometry
type: Concept
broader: Photometric systems
narrower: H alpha photometry
narrower: H beta photometry

Natural satellites (Solar system)
type: Concept
alternative label: Planet satellites
alternative label: Planetary satellites
alternative label: Secondary planets
broader: Solar system
narrower: Martian satellites
narrower: Neptunian satellites
narrower: Saturnian satellites
narrower: The Moon
narrower: Uranian satellites
narrower: Jovian satellites
alternative label: Moons (Solar system)
related: Natural satellites (Extrasolar)
narrower: Irregular satellites
definition: A solar system object that revolves around a primary body and is not man made.
contributor: AAS Frey.Katie Admin
narrower: Plutonian satellites
narrower: Asteroid satellites
related: Natural satellite dynamics
related: Natural satellite formation
related: Natural satellite surfaces
related: Natural satellite atmospheres
modified: 2022-06-21T17:44:41.762Z
related: Solar system planets
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T19:39:45.309Z
  creator: AAS Frey.Katie
modified: 2020-11-10T19:39:45.340Z

Ataxites
type: Concept
broader: Meteorites

Nautical almanacs
type: Concept
broader: Almanacs

Navarro-Frenk-White profile
type: Concept
alternative label: NFW
alternative label: NFW profile
alternative label: NFW-profile
broader: Galaxy mass distribution
related: Dark matter

Near-Earth objects
type: Concept
alternative label: NECs
alternative label: NEOs
alternative label: Near-Earth asteroids
alternative label: Near-Earth comets
narrower: Aten group
narrower: Atira group
narrower: Amor group
narrower: Earth trojans
narrower: Apollo group
related: Close encounters
alternative label: Near Earth objects
definition: An asteroid, comet, or large meteoroid whose orbit brings it exceptionally close to the Earth, and which may therefore pose a collision danger. Most such objects are in orbits around the Sun with perihelion distance less than 1.3 astronomical units.
contributor: AAS Frey.Katie Admin
broader: Small Solar System bodies
related: Asteroids
related: Comets
modified: 2020-12-04T18:07:50.917Z
modified: 2020-11-03T19:29:51.492Z
editorial note: Definition Provenance
  created: 2020-11-03T19:29:51.462Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Near infrared astronomy
type: Concept
alternative label: Near infrared astronomical observations
alternative label: Near infrared telescopes
alternative label: Near ir astronomical observations
alternative label: Near ir astronomy
alternative label: Near-infrared astronomical observations
alternative label: Near-infrared astronomy
alternative label: Near-infrared telescopes
alternative label: Near-ir astronomical observations
alternative label: Near-ir astronomy
broader: Infrared astronomy

Near ultraviolet astronomy
type: Concept
alternative label: Near ultraviolet astronomical observations
alternative label: Near ultraviolet telescopes
alternative label: Near uv astronomical observations
alternative label: Near uv astronomy
alternative label: Near-ultraviolet astronomical observations
alternative label: Near-ultraviolet astronomy
alternative label: Near-ultraviolet telescopes
alternative label: Near-uv astronomical observations
alternative label: Near-uv astronomy
broader: Ultraviolet astronomy

Nebulae
type: Concept
alternative label: Nebula
broader: Interstellar medium
narrower: Pre-solar nebulae
narrower: Protoplanetary nebulae
narrower: Reflection nebulae
narrower: Ring nebulae
narrower: Bipolar nebulae
narrower: Supernova remnants
narrower: Bright nebulae
narrower: Cometary nebulae
narrower: Compact nebulae
narrower: Dark interstellar clouds
narrower: Diffuse nebulae
narrower: Dust nebulae
narrower: Emission nebulae
narrower: Filamentary nebulae
narrower: Gaseous nebulae
narrower: H I regions
definition: A cloud of gas and dust in the interstellar space.
narrower: Pulsar wind nebulae
modified: 2022-01-03T15:01:11.724Z
contributor: AAS Frey.Katie
modified: 2020-11-02T16:30:32.644Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:30:32.609Z
contributor: AAS Frey.Katie Admin

Neptune
type: Concept
broader: Solar system gas giant planets
related: Neptunian satellites
definition: The eighth planet from the Sun and the fourth largest by size in the solar system. The equatorial radius of Neptune is 24,764 km (3.883 Earths), its semi-major axis is 30.11 astronomical units (4.50 x 10^9 km), and its orbital period is 164.8 yr. Neptune has at least 14 moons, the largest ones are Triton, Proteus, and Nereid, whereas its smaller moons are: Naiad, Thalassa, Despina, Galatea, Larissa, Halimede, Sao, Laomedeia, Psamathe, and Neso. Neptune has an incredibly thick atmosphere comprised of 74% hydrogen, 25% helium, and approximately 1% methane. Particles of icy methane in its upper atmosphere give Neptune its deep blue color. Large storms whirl through Neptune's upper atmosphere, and high-speed winds track around the planet at up 600 m/s, fastest recorded in the solar system. One of the largest storms ever seen was recorded in 1989. Called the Great Dark Spot, it lasted about five years. Neptune has a very thin collection of rings. They are likely made up of ice particles mixed with dust grains and possibly coated with a carbon-based substance.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:19:05.278Z
modified: 2020-11-10T19:41:43.352Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T19:41:43.320Z
  creator: AAS Frey.Katie

Neptune trojans
type: Concept
broader: Trans-Neptunian objects
broader: Trojan asteroids

Neptunian satellites
type: Concept
alternative label: Moons of Neptune
alternative label: Neptunian moons
alternative label: Nereid
broader: Natural satellites (Solar system)
related: Neptune
contributor: AAS Frey.Katie Admin
narrower: Triton
example: Naiad
example: Thalassa
example: Nereid
modified: 2020-12-09T15:22:55.259Z

Neutral hydrogen clouds
type: Concept
alternative label: HI clouds
alternative label: Neutral atomic hydrogen clouds
broader: Interstellar clouds

Abundance ratios
type: Concept
broader: Chemical abundances
contributor: AAS Frey.Katie
definition: The relative amount of a given chemical element with respect to other elements.
modified: 2020-11-02T17:18:26.234Z
editorial note: Definition Provenance
  created: 2020-11-02T17:18:57.494Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-02T17:18:57.522Z

Aten group
type: Concept
alternative label: Aten asteroids
alternative label: Atens
broader: Near-Earth objects
definition: A member of a class of near-Earth asteroids with perihelion distances between 0.983 and 1.0 astronomical units. It is estimated that 6% of the total number of NEAs are Atens.
modified: 2020-10-26T18:58:42.748Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T18:58:53.901Z
modified: 2020-10-26T18:58:53.928Z

Neutrino astronomy
type: Concept
broader: Astronomical methods
broader: High energy astrophysics
narrower: Neutrino masses
narrower: Solar neutrino problem
narrower: Urca process

Neutrino decoupling
type: Concept
broader: Early universe

Neutrino masses
type: Concept
broader: Neutrino astronomy

Neutrino oscillations
contributor: AAS Frey.Katie Admin
type: Concept
broader: Nuclear astrophysics
broader: Particle astrophysics
modified: 2020-12-16T15:44:57.600Z

Neutrino telescopes
type: Concept
broader: Telescopes

Neutron interferometry
type: Concept
broader: Interferometry

Neutron star cores
type: Concept
alternative label: Neutron star core
broader: Neutron stars

Newtonian cosmology
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
definition: The use of Newtonian mechanics to derive homogeneous and isotropic solutions of Einstein's field equations, which represent models of expanding Universe. The Newtonian cosmology deviates from the prediction of general relativity in the general case of anisotropic and inhomogeneous models.
modified: 2020-11-10T19:42:16.603Z
modified: 2020-11-10T19:42:26.898Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T19:42:26.867Z

Atira group
type: Concept
alternative label: Apohele asteroids
alternative label: Apohele group
alternative label: Atiras
broader: Near-Earth objects

Newtonian gravitation
type: Concept
broader: Gravitation
narrower: Accretion
narrower: Gravitational disruption
narrower: Gravitational energy
narrower: Gravitational equilibrium
narrower: Gravitational fields
narrower: Gravitational instability
narrower: Gravitational interaction
narrower: Gravity anomaly

Newtonian telescopes
type: Concept
broader: Reflecting telescopes
narrower: Dobsonian telescopes

Night sky brightness
type: Concept
alternative label: Night sky background
broader: Sky brightness
narrower: Gegenschein
narrower: Light pollution

Night vision
type: Concept
broader: Amateur astronomy

Nitrous oxide
type: Concept
alternative label: Laughing gas
alternative label: N2O
alternative label: Sweet air
broader: Greenhouse gases

Non-Gaussianity
type: Concept
broader: Cosmology
related: Cosmic microwave background radiation

Non-radial pulsations
type: Concept
alternative label: Nonradial pulsation
broader: Stellar pulsations

Non-standard theories of gravity
type: Concept
broader: Gravitation
narrower: Modified Newtonian dynamics
narrower: Quantum gravity
narrower: Scalar-tensor-vector gravity
narrower: Two-dimensional gravity

Non-thermal radiation sources
type: Concept
alternative label: Non-thermal sources
alternative label: Nonthermal sources
broader: Astronomical radiation sources

Atmospheric circulation
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: The large-scale movements of air around areas of high and low pressure whereby heat is distributed on the surface of the Earth. Atmospheric motion is driven by uneven heating of the planet. The atmosphere (and ocean) transfers the excess heat from tropics to poles. The flow is determined by balance between pressure gradients and the Coriolis effect.
modified: 2020-11-03T18:32:42.399Z
editorial note: Definition Provenance
  created: 2020-11-03T18:32:58.032Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:32:58.064Z

Nonclassical interferometry
type: Concept
alternative label: Non-classical interferometry
broader: Interferometry

Nonrotating black holes
type: Concept
alternative label: Non-rotating black holes
broader: Classical black holes
narrower: Reissner-Nordström black holes
narrower: Schwarzschild black holes

Nonstandard evolution
type: Concept
broader: Stellar evolution

North celestial pole
type: Concept
alternative label: N.C.P.
alternative label: NCP
broader: Celestial poles
contributor: AAS Frey.Katie
definition: The point in the northern hemisphere where the rotation axis of Earth touches the celestial sphere. The star Polaris, also called the Pole Star, is located very near this point, at an angular separation of 42 arcminutes (about 1.4 lunar diameters).
modified: 2020-11-10T19:43:24.582Z
editorial note: Definition Provenance
  created: 2020-11-10T19:43:34.092Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-10T19:43:34.122Z

North ecliptic pole
type: Concept
alternative label: N.E.P.
alternative label: NEP
broader: Ecliptic poles

North galactic pole
type: Concept
alternative label: N.G.P.
alternative label: NGP
broader: Galactic poles

Novae
type: Concept
broader: Stellar types
broader: Cataclysmic variable stars
narrower: Recurrent novae
narrower: Slow novae
narrower: Symbiotic novae
narrower: X-ray novae
narrower: Classical novae
narrower: Dwarf novae
narrower: Fast novae
related: Optical bursts
narrower: DQ Herculis stars
broader: Stellar remnants
contributor: AAS Frey.Katie Admin
definition: A star that experiences a sudden increase in luminosity, by a s much as 10^6. The outburst ejects a shell of matter but does not disrupt the star.
modified: 2020-11-03T19:43:17.433Z
editorial note: Definition Provenance
  created: 2020-11-03T19:44:00.136Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:44:00.165Z

Nuclear abundances
type: Concept
broader: Chemical abundances

Atmospheric effects
type: Concept
broader: Atmospheric science
narrower: Seasonal phenomena
narrower: Sky brightness

Nucleated dwarf galaxies
type: Concept
broader: Dwarf galaxies

Nucleosynthesis
type: Concept
alternative label: Element formation
alternative label: Formation of elements
broader: Nuclear astrophysics
narrower: Oxygen burning
narrower: P-process
narrower: R-process
narrower: S-process
narrower: Silicon burning
narrower: Big Bang nucleosynthesis
narrower: Stellar nucleosynthesis
narrower: Carbon burning
narrower: Cosmic ray nucleosynthesis
narrower: Explosive nucleosynthesis
narrower: Helium burning
narrower: Hydrogen burning
contributor: AAS Frey.Katie
definition: The process by which nuclear reactions at very high temperatures and pressures produce the various chemical elements of the periodic table, either in the Big Bang or in stellar interiors.
modified: 2020-11-10T19:44:58.436Z
editorial note: Definition Provenance
  created: 2020-11-10T19:45:08.176Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-10T19:45:08.204Z

O associations
type: Concept
alternative label: O-association
broader: Stellar associations

O clusters
type: Concept
alternative label: O-clusters
broader: Open star clusters

T dwarfs
broader: Dwarf stars
type: Concept
alternative label: T dwarf stars
broader: Brown dwarfs
broader: Late-type dwarf stars
alternative label: T-type brown dwarfs
alternative label: T brown dwarfs
contributor: AAS Frey.Katie Admin
definition: A type of brown dwarf with an effective temperature between about 1200 K and 500 K, i.e. colder than the preceding type L dwarf. The spectra of T dwarfs are characterized by the presence of methane bands in the near infrared. The presence of these bands, broad H_{2}O features, and H_2 collision-induced absorption radically alter the spectral energy distributions of T dwarfs compared to a black body at the same temperature. Hence near-infrared colors become increasingly blue (J - K ~ 0) as compared to L dwarfs. The first T dwarf, called Gl 229B, was discovered by Nakajima et al. The spectral classification scheme (subtypes T0 to T9) currently used was defined by Burgasser et al.
preferred label: T dwarves
modified: 2021-09-27T15:42:06.537Z
modified: 2020-11-04T19:46:01.009Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T19:46:00.981Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

O stars
broader: Stellar spectral types
type: Concept
alternative label: Class O stars
alternative label: O-type stars
broader: Early-type stars
narrower: O subgiant stars
narrower: O dwarf stars
narrower: O giant stars
narrower: O subdwarf stars
narrower: O supergiant stars
narrower: Oe stars
narrower: Oef stars
narrower: Of stars
related: Stellar classification
contributor: AAS Frey.Katie Admin
definition: A luminous, hot, blue star whose spectrum is dominated by the lines of hydrogen, atomic helium, and ionized helium; also known as O-type star. This is the earliest spectral type and the only main sequence star in which ionized helium is present. The effective temperatures of these stars range from about 30,000 K to 50,000 K, their luminosities from 50,000 to 1,000,000 times that of solar luminosity, and their masses from about 20 to 100 solar masses. The hottest O-type stars display high ionization emission features such as N III and He II, Of star. They are divided into subtypes O2, the hottest, to O9.7, the coldest. O-type stars are relatively rare, for each star of 100 solar masses there are 10^6 stars of solar mass. They are relatively short-lived since they spend only a few million years on the main sequence. The brightest O-type star in the sky visible with naked eye is Alnitak.
modified: 2020-11-03T19:46:55.553Z
modified: 2020-11-03T19:47:07.379Z
editorial note: Definition Provenance
  created: 2020-11-03T19:47:07.351Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

B stars
broader: Stellar spectral types
alternative label: B type stars
type: Concept
alternative label: B-type stars
alternative label: Class B stars
alternative label: Type-B stars
broader: Early-type stars
narrower: Mercury-manganese stars
narrower: B subgiant stars
narrower: B dwarf stars
narrower: B giant stars
narrower: B subdwarf stars
narrower: B supergiant stars
narrower: Be stars
narrower: Bp stars
narrower: BW stars
narrower: 53 Persei stars
related: Stellar classification
definition: A star of spectral type B, whose spectrum is marked by absorption lines of hydrogen; also known as B-type star. B-type optical spectra are characterized by the presence of neutral He lines (mainly He I 4471 Å) at about type B9. He I strengthens up to about B2, then decreases. Ionized helium (mainly He II 4541 Å) first appears at about B0. Most metallic lines are absent or weak, except some absorption lines for the higher ionization states of silicon, oxygen, carbon, and magnesium. These are hot stars with effective temperatures ranging from about 10,000 K at B9 to nearly 30,000 K at B0. They are between 3 and 20 solar masses. Some famous examples include Rigel, Achernar, and Hadar.
contributor: AAS Frey.Katie
modified: 2020-10-26T19:00:17.903Z
editorial note: Definition Provenance
  created: 2020-10-26T19:00:28.450Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-26T19:00:28.476Z

Atmospheric extinction
type: Concept
broader: Extinction
narrower: Ultraviolet extinction
related: Earth atmosphere
scope note: Refers to earth atmosphere
modified: 2020-11-03T18:34:08.347Z
contributor: AAS Frey.Katie
definition: The decrease in the intensity of light from a celestial body due to absorption and scattering by Earth's atmosphere. It increases from the zenith to the horizon and affects short wavelengths more than long wavelengths, so that objects near the horizon appear redder than they do at the zenith.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:34:30.935Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:34:30.966Z

OB associations
type: Concept
broader: Stellar associations
definition: A loosely bound grouping of O and B stars that typically stretches up to several hundred light-years and may contain between a dozen and several hundred O stars and B stars. The members of an OB association are young and of roughly the same age. OB associations dissipate in a few tens of millions of years.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T20:24:25.080Z
modified: 2020-11-05T20:24:41.107Z
editorial note: Definition Provenance
  created: 2020-11-05T20:24:41.071Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

OB stars
type: Concept
broader: Early-type stars
narrower: OB supergiant stars
related: Stellar classification
broader: Stellar spectral types
alternative label: OB-type stars
definition: A collective designation for massive O and B stars.
modified: 2020-10-26T19:00:57.650Z
contributor: AAS Frey.Katie
modified: 2020-10-26T19:01:09.117Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T19:01:09.089Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Oblateness
type: Concept
alternative label: Ellipticity
alternative label: Flattening
broader: Planetary structure
contributor: AAS Frey.Katie
definition: The property possessed by a round body that is flattened at the poles.
modified: 2020-11-17T19:00:34.784Z
modified: 2020-11-17T19:00:48.978Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:00:48.952Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Oblique rotators
type: Concept
broader: Asteroseismology

Observational astronomy
type: Concept
alternative label: Imaging of stars
alternative label: Stellar imaging
narrower: Astronomical methods
narrower: Astronomical techniques
narrower: Astronomical instrumentation
narrower: Astronomical research
top concept of: The Unified Astronomy Thesaurus
contributor: AAS Frey.Katie Admin
modified: 2023-02-03T18:28:24.077Z

Observational cosmology
type: Concept
broader: Astronomical methods
broader: Cosmology
narrower: Cosmological constant
narrower: Hubble constant
contributor: AAS Frey.Katie
definition: The application of observational data to the study of the Universe as a whole.
modified: 2020-11-17T19:01:23.031Z
modified: 2020-11-17T19:01:33.091Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:01:33.066Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Observatories
type: Concept
broader: Astronomical instrumentation
narrower: Optical observatories
narrower: Radio observatories
narrower: Solar observatories
narrower: Space observatories
narrower: Ultraviolet observatories
narrower: X-ray observatories
narrower: Domes
narrower: Antarctic observatories
narrower: Gamma-ray observatories
narrower: Infrared observatories
narrower: Virtual observatories
related: Astronomical site protection
contributor: AAS Frey.Katie Admin
modified: 2022-06-16T14:22:14.733Z

Occultation
type: Concept
broader: Syzygy
narrower: Occulting disks
narrower: Radio occultation
narrower: Asteroid occultation
narrower: Lunar occultation
related: Transits
narrower: Stellar occultation
contributor: AAS Frey.Katie
definition: The blocking of light from an astronomical object, such as a star, by another object, such as the Moon or an asteroid, that passes in front of it. Also, the period of time for which this blocking takes place. A solar eclipse is a particular case of occultation. Determining the moment of stellar occultation by the Moon is used to improve our knowledge of the lunar orbit. Moreover, the occultation of stars by asteroids or planetary satellites provide important data for better measuring the sizes of the occulting bodies.
modified: 2020-11-17T19:02:13.945Z
modified: 2020-11-17T19:02:25.898Z
editorial note: Definition Provenance
  created: 2020-11-17T19:02:25.872Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Occulting disks
type: Concept
alternative label: Occulting discs
broader: Occultation

Atmospheric refraction
type: Concept
broader: Astronomical optics
contributor: AAS Frey.Katie
modified: 2020-11-03T18:35:15.617Z
definition: The shift in apparent direction of a celestial object caused by the bending of light while passing through the Earth's atmosphere. Since the density of the atmosphere decreases with altitude, the starlight will bend more as it continues down through the atmosphere. As a result, a star will appear higher in the sky than its true direction.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:35:27.294Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:35:27.334Z

Ocean-atmosphere interactions
type: Concept
broader: Earth atmosphere

Ocean planets
type: Concept
alternative label: Water worlds
broader: Exoplanets
definition: A hypothetical exoplanet covered by a water envelope. The presence of such a planet stems from the implicit assumption of Habitable Zone temperatures and a liquid water surface.
modified: 2020-11-03T19:53:47.154Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T19:54:01.110Z
editorial note: Definition Provenance
  created: 2020-11-03T19:54:01.085Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Ocean tides
type: Concept
alternative label: Diurnal
alternative label: Semi-diurnal
broader: Tides
narrower: Polar tides

Of stars
type: Concept
alternative label: Of type stars
alternative label: Of-type stars
broader: O stars
broader: Early-type emission stars
definition: An O star whose spectrum displays strong N III 4634-4640-4642 emission and strong He II 4686 emission. The N III lines are always much stronger than C III 4647-4650-4651 when the latter are present. Historically, Of stars were considered to belong to the peculiar category, hence the f notation (see below). In his thesis work, Walborn removed them from that category and established them as the normal O-type supergiants. He also used the notation ((f)), (f), and f to describe the progression from strong He II 4686 absorption, through weakened/absent, to emission, respectively, correlated with increasing N III emission strength, subsequently showing that it is a luminosity sequence -- the first such for stars earlier than O9.
modified: 2020-11-05T20:26:32.413Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T20:26:46.364Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T20:26:46.329Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

OH/IR stars
type: Concept
alternative label: OH-IR stars
broader: Giant stars
related: Cocoon stars
related: Hydroxyl sources
related: Infrared sources
definition: An evolved Mira-type star which is associated with strong OH maser and strong infrared (IR) emission from the surrounding shell of warm gas and dust.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:05:31.368Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:05:42.988Z
modified: 2020-11-03T21:05:43.019Z

Oort cloud
type: Concept
alternative label: Oort Cloud
alternative label: Opik-Oort Cloud
alternative label: Öpik–Oort cloud
broader: Solar system
broader: Long period comets
narrower: Oort cloud objects
contributor: AAS Frey.Katie
modified: 2020-11-17T19:04:05.986Z
definition: A huge theoretical cloud of comets surrounding the Sun between about 50,000 and 100,000 astronomical units and thought to be the reservoir of long-period comets entering the inner solar system.
editorial note: Definition Provenance
  created: 2020-11-17T19:04:16.728Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:04:16.758Z

Oort cloud objects
type: Concept
alternative label: OCOs
broader: Oort cloud

Oort constants
type: Concept
broader: Galaxy rotation
broader: Astronomical models
related: Milky Way Galaxy
related: Galactic center
definition: Two parameters, denoted A and B, that describe the major features of our Galaxy's differential rotation in the Sun's neighbourhood. A is one-half of the shear and equal to +14.4 ± 1.2 km s^-1 kpc^-1, and B, one-half of the vorticity, equal to -12.0 ± 2.8 km s^-1 pc^-1.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:00:36.974Z
modified: 2020-11-03T20:00:49.209Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:00:49.180Z

Atmospheric science
type: Concept
broader: Planetary science
narrower: Atmospheric effects
narrower: Aeronomy
related: Planetary atmospheres
modified: 2020-12-11T18:31:08.727Z
contributor: AAS Frey.Katie Admin

Open star clusters
type: Concept
alternative label: Open clusters
narrower: O clusters
narrower: Young star clusters
broader: Star clusters
definition: A loose grouping of dozens or hundreds of young stars distributed in a region a few light-years across. Open clusters are relatively young, typically containing many hot, highly luminous stars. They are located within the disk of the Galaxy, whence their older name Galactic clusters.
modified: 2020-11-03T19:54:49.086Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T19:55:00.400Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T19:55:00.426Z

Open universe
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
definition: A Freidmann-Lemaitre cosmological model in which space is infinite and of negative curvature or Euclidean, and which expands forever.
modified: 2020-11-17T19:05:38.587Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:05:49.493Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:05:49.529Z

Opik theory
type: Concept
alternative label: Opik's theory
alternative label: Öpik theory
alternative label: Öpik's theory
broader: Close encounters

Opposition
type: Concept
broader: Astronomical location
scope note: Refers to planet position
contributor: AAS Frey.Katie
definition: The position of a solar system body having its orbit outside that of the Earth when the Earth is in a line between the Sun and the body. At opposition the body has a solar elongation of 180°, and is closest to the Earth. It will, in principle, be visible throughout the night. It will rise in the east as the Sun sets in the west and it will set as the Sun rises. This is because, at opposition, the body and the Sun are 12 hours apart. The inner planets can never be in opposition. The opposite of opposition is conjunction.
modified: 2020-11-17T19:06:23.648Z
editorial note: Definition Provenance
  created: 2020-11-17T19:06:33.610Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:06:33.643Z

Optical bursts
type: Concept
alternative label: Optical outbursts
alternative label: Outbursts
broader: Burst astrophysics
related: Novae
related: Binary stars

Optical double stars
type: Concept
related: Binary stars
scope note: Use only for pair in chance alignment; refer also to visual binary stars
alternative label: Optical doubles
definition: A pair of stars that lie close to each other in the sky by chance, but are not physically associated, in contrast to a true binary star.
contributor: AAS Frey.Katie Admin
broader: Optical observation
modified: 2020-12-04T14:58:14.297Z
editorial note: Definition Provenance
  created: 2020-11-03T19:55:54.189Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T19:55:54.214Z

Optical flares
type: Concept
broader: Stellar flares

Optical identification
type: Concept
alternative label: Optical counterparts
broader: Optical astronomy
contributor: AAS Frey.Katie Admin
modified: 2020-11-09T22:09:56.070Z

Optical interferometry
type: Concept
alternative label: Light interferometry
alternative label: Stellar interferometry
broader: Interferometry
narrower: Optical phase shifting interferometry

Optical observation
type: Concept
broader: Astronomical techniques
narrower: Center to limb observations
contributor: AAS Frey.Katie Admin
narrower: Optical double stars
scope note: Astronomy using the (human) eye as the primary detector; this includes both naked-eye observations and observations through telescopes without further instrumentation (like cameras, spectrographs, etc).
alternative label: Visual observation
modified: 2020-12-16T20:46:30.456Z

Atmospheric scintillation
type: Concept
alternative label: Terrestrial scintillation
broader: Astronomical optics
narrower: Ionospheric scintillation

Optical observatories
type: Concept
broader: Observatories
narrower: Hubble Space Telescope
narrower: Very Large Telescope
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T20:04:35.380Z

Optical phase shifting interferometry
type: Concept
alternative label: Optical phase-shifting interferometry
alternative label: Phase shifting interferometry
alternative label: Phase-shifting interferometry
broader: Optical interferometry
narrower: Michelson interferometry
narrower: Mach-Zehnder interferometers

Optical position
type: Concept
broader: Astronomical location

Optical pulsars
type: Concept
broader: Pulsars
definition: A member of a rare class of pulsars, such as the Crab pulsar and Vela pulsar, which can be detected in the visible spectrum.
modified: 2020-11-03T19:56:37.818Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T19:56:49.373Z
editorial note: Definition Provenance
  created: 2020-11-03T19:56:49.342Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Optical telescopes
type: Concept
broader: Telescopes
narrower: Multiple mirror telescopes
narrower: Reflecting telescopes
narrower: Refracting telescopes
narrower: Solar optical telescopes
narrower: Catadioptric telescopes
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T20:05:23.958Z
narrower: Eye pieces

Orbit determination
type: Concept
broader: Orbits

Orbital anomalies
type: Concept
alternative label: Apparent anomaly
broader: Orbital elements
narrower: Mean anomaly
narrower: True anomaly
narrower: Eccentric anomaly

Orbital elements
type: Concept
alternative label: Keplerian elements
broader: Orbits
narrower: Orbital anomalies
narrower: Osculatory elements
narrower: Position angle
narrower: Synodic period
narrower: Center of mass
narrower: Eccentricity
narrower: Elliptical orbits
narrower: Apsides
narrower: Argument of perigee
narrower: Argument of perihelion
narrower: Inclination
narrower: Longitude of the ascending node
narrower: Longitude of the descending node
contributor: AAS Frey.Katie
definition: A fixed point in a body through which the resultant force of gravitational attraction acts.
modified: 2020-11-17T19:09:09.607Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:09:19.702Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:09:19.736Z

Orbital evolution
type: Concept
broader: Cosmological evolution

Orbital motion
type: Concept
broader: Orbits
narrower: Osculating orbit
narrower: Parabolic orbit
narrower: Periodic orbit
narrower: Polar orbit
narrower: Circular orbits
narrower: Elliptical orbits
narrower: Equation of the center
narrower: Apsidal motion
narrower: Geocentric orbit
narrower: Heliocentric orbit
narrower: Hyperbolic orbit
narrower: Keplerian orbit
narrower: Libration
narrower: Lunar node regression
narrower: Analemma
narrower: Prograde orbit
narrower: Retrograde orbit

Atmospheric tides
type: Concept
broader: Planetary atmospheres
broader: Tides
broader: Earth atmosphere

Orbital nodes
type: Concept
alternative label: Line of node
broader: Orbits
narrower: Descending node
narrower: Ascending node
definition: One of the two points of intersection of the orbit of a secondary body with the plane of reference through the primary.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:02:32.970Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:02:45.955Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T20:02:45.979Z

Orbital resonances
type: Concept
alternative label: Orbital resonance gaps
broader: Orbits
broader: Gravitational interaction
narrower: Kirkwood gaps

Orbital theory
type: Concept
broader: Orbits
narrower: Bode's law

Orbiters
type: Concept
broader: Space probes
definition: A spacecraft or satellite designed to orbit a planet or other solar system body.
modified: 2020-11-03T20:03:39.342Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:03:53.467Z
modified: 2020-11-03T20:03:53.497Z

Orbits
type: Concept
alternative label: Orbital dynamics
broader: Celestial mechanics
narrower: Orbit determination
narrower: Orbital elements
narrower: Orbital motion
narrower: Orbital nodes
narrower: Orbital resonances
narrower: Orbital theory
definition: The path followed by a body moving in a gravitational field. For bodies moving under the influence of a centrally directed force, without significant perturbation, the shape of the orbit must be one of the conic section family of curves (circle, ellipse, parabola, or hyperbola).
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:01:40.537Z
narrower: Spin-orbit resonances
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:01:53.075Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T20:01:53.103Z

Origin of the universe
type: Concept
alternative label: Formation of the universe
broader: Cosmology
narrower: Big Bang theory
narrower: Steady-state theory
narrower: Early universe
narrower: Hubble-Lemaitre law

Orreries
type: Concept
broader: Early astronomical instruments
alternative label: Orrery
contributor: AAS Frey.Katie Admin
definition: A mechanical device that illustrates the relative positions and motions of the planets and moons in the solar system in heliocentric model.
modified: 2020-11-03T20:17:37.408Z
editorial note: Definition Provenance
  created: 2020-11-03T20:17:51.848Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T20:17:51.875Z

Oscillating universe
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
definition: A cosmological model in which the Universe is closed and undergoes a series of oscillations, each beginning with a big bang and ending with a big crunch.
modified: 2020-11-17T19:13:31.122Z
modified: 2020-11-17T19:13:40.568Z
editorial note: Definition Provenance
  created: 2020-11-17T19:13:40.539Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Osculating orbit
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
definition: The Keplerian orbit that a satellite would follow after a specific time t if all forces other than central inverse-square forces ceased to act from time t on. An osculating orbit is tangent to the real, perturbed, orbit and has the same velocity at the point of tangency.
modified: 2020-11-17T19:14:13.783Z
editorial note: Definition Provenance
  created: 2020-11-17T19:14:23.326Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:14:23.356Z

Osculatory elements
type: Concept
broader: Orbital elements

Solar system gas giant planets
type: Concept
broader: Solar system planets
narrower: Neptune
narrower: Saturn
narrower: Uranus
narrower: Jupiter
definition: A planet that revolves around the Sun beyond the asteroid belt, namely Jupiter, Saturn, Uranus, and Neptune.
contributor: AAS Frey.Katie Admin
alternative label: Outer planets
alternative label: Gas giants
related: Extrasolar gaseous giant planets
alternative label: Jovian planets
modified: 2020-11-09T21:34:59.978Z
modified: 2020-11-03T20:18:44.612Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:18:44.583Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Oxygen burning
type: Concept
broader: Nucleosynthesis
contributor: AAS Frey.Katie
definition: The stage when a star fuses oxygen into silicon and sulfur. It occurs only in massive stars, with a mass over eight solar masses.
modified: 2020-11-17T19:15:12.334Z
modified: 2020-11-17T19:15:22.183Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:15:22.154Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Ozone layer
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: An atmospheric layer that contains a high proportion of oxygen that exists as ozone. It acts as a filtering mechanism against incoming ultraviolet radiation. It is located between the troposphere and the stratosphere, around 15 to 20 kilometers above the Earth's surface.
modified: 2020-10-21T14:29:24.723Z
modified: 2020-10-21T14:30:00.808Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-21T14:30:00.780Z

P-process
type: Concept
broader: Nucleosynthesis

Parabolic orbit
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
definition: An orbit whose overall shape is like a parabola; it is the limiting case between an elliptical orbit (eccentricity less than 1) and a hyperbolic orbit (eccentricity larger than 1). The speed necessary to form a parabolic orbit is known as the escape velocity.
modified: 2020-10-21T14:30:53.206Z
modified: 2020-10-21T14:31:08.601Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-21T14:31:08.576Z

Parallax
type: Concept
broader: Astrometry
narrower: Moving cluster parallax
narrower: Photometric parallax
narrower: Secular parallax
narrower: Statistical parallax
narrower: Stellar parallax
narrower: Trigonometric parallax
narrower: Diurnal parallax
narrower: Annual parallax
narrower: Dynamical parallax
narrower: Kinematic parallax
related: Microlensing parallax
contributor: AAS Frey.Katie
definition: The apparent shift of a nearby object's position in relation to more distant ones when the nearby object is observed from different viewing angles.
modified: 2020-10-21T14:37:25.370Z
modified: 2020-10-21T14:37:40.593Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-21T14:37:40.566Z

Parsec
type: Concept
alternative label: Parallax second
broader: Distance measure
definition: A basic unit of astronomical distances, corresponding to a trigonometric parallax of one second of arc. In other words, it is the distance at which one astronomical unit (the mean radius of the Earth's orbit) subtends an angle of 1 arcsecond. 1 pc = 3.2616 light-years = 206,265 astronomical units = 30.857 x 10^12 km.
modified: 2020-11-03T20:20:27.603Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:20:43.508Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:20:43.476Z

Accelerating universe
type: Concept
broader: Deceleration parameter
contributor: AAS Frey.Katie
modified: 2020-11-03T17:45:49.551Z
definition: The deduction based on the observation that the most distant Type Ia supernovae are fainter than that expected from their redshifts in a matter-only dominated expanding Universe. The faintness is attributed to larger distances resulting from an accelerating Universe driven by presence of a new component with strongly negative pressure. This component that makes the Universe accelerate is named dark energy.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T17:46:10.501Z
  creator: AAS Frey.Katie
modified: 2020-11-03T17:46:10.529Z

Australites
type: Concept
broader: Tektites

Partial eclipses
type: Concept
broader: Eclipses
definition: An eclipse that is not total.
modified: 2020-11-03T20:19:12.641Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T20:19:26.582Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T20:19:26.615Z

Penrose limit
type: Concept
broader: Geodesics

Penrose process
type: Concept
alternative label: Penrose mechanism
broader: Black hole physics
contributor: AAS Frey.Katie
definition: A hypothetical means of extracting energy from a rotating black hole. If a particle spirals into the ergosphere of a black hole in a direction counter to the rotation of the black hole, and if the particle then breaks up into two fragments inside the ergosphere, one of the fragments can escape with energy greater than the energy of the original particle.
modified: 2020-11-17T19:18:16.725Z
modified: 2020-11-17T19:18:26.638Z
editorial note: Definition Provenance
  created: 2020-11-17T19:18:26.609Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Penumbra
type: Concept
alternative label: Penumbras
broader: Eclipses
contributor: AAS Frey.Katie
definition: The portion of a shadow in which light from an extended source is partially but not completely cut off by an intervening body; the area of partial shadow surrounding the umbra. The lighter part of a shadow during an eclipse. An observer standing in the penumbra of a Solar eclipse will see a partial eclipse.
modified: 2020-11-17T19:19:56.818Z
modified: 2020-11-17T19:20:06.826Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:20:06.798Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Periapsis
type: Concept
alternative label: Pericenter
broader: Apsides
contributor: AAS Frey.Katie
definition: The point in an orbit of a body where it is closest to its primary; opposite of apoapsis.
modified: 2020-11-17T19:20:38.854Z
modified: 2020-11-17T19:20:48.918Z
editorial note: Definition Provenance
  created: 2020-11-17T19:20:48.889Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Periastron
type: Concept
broader: Apsides
contributor: AAS Frey.Katie
definition: In a binary system, the point in the orbit where a component is nearest the other component; opposite of apastron.
modified: 2020-11-17T19:23:32.595Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:23:41.878Z
  creator: AAS Frey.Katie
modified: 2020-11-17T19:23:41.910Z

Perigee
type: Concept
broader: Apsides
contributor: AAS Frey.Katie
definition: The point in the orbit of a body revolving around the Earth at which it is nearest to the Earth; opposite of apogee.
modified: 2020-11-17T19:24:09.933Z
modified: 2020-11-17T19:24:20.547Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:24:20.521Z
  creator: AAS Frey.Katie

Automated telescopes
type: Concept
alternative label: Robotic telescope
broader: Telescopes
narrower: Automatic patrol telescopes

Perihelion
type: Concept
broader: Apsides
contributor: AAS Frey.Katie
definition: The nearest point to the Sun in an orbit around the Sun; opposite of aphelion.
modified: 2020-11-17T19:24:45.569Z
modified: 2020-11-17T19:24:59.170Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:24:59.145Z
  creator: AAS Frey.Katie

Period determination
type: Concept
broader: Apparent magnitude

Periodic orbit
type: Concept
broader: Orbital motion

Perseus Cluster
type: Concept
broader: Galaxy clusters
contributor: AAS Frey.Katie
definition: A galaxy cluster of about 12,000 members about 250 million light-years (redshift z = 0.0176) away, covering 4° of sky in the constellation Perseus. It is dominated by elliptical galaxies. At its center lies the radio source Perseus A. Also known as Abell 426 (Abell catalog).
modified: 2020-11-17T19:25:30.789Z
modified: 2020-11-17T19:25:43.603Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T19:25:43.575Z

Perturbation methods
type: Concept
alternative label: Perturbation theory
broader: Celestial mechanics
broader: Analytical mathematics
related: Cosmological perturbation theory

PG 1159 stars
type: Concept
alternative label: GW Virginis stars
alternative label: Pg 1159-35 stars
broader: Multi-periodic variable stars
broader: DO stars

Phase angle
type: Concept
broader: Astrometry
contributor: AAS Frey.Katie
definition: For an object in the solar system, the angle "Sun-object-Earth" that is, the angle between the Sun and the observer as seen from the given object. It is 0° when the object is fully illuminated, 90° when the object is half-illuminated (like the Moon at first quarter and last quarter), and 180° when the object is between Earth and the Sun.
modified: 2020-11-17T19:26:13.256Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:26:26.973Z
  creator: AAS Frey.Katie
modified: 2020-11-17T19:26:27.003Z

Phase defect
type: Concept
broader: Astrometry

Phase effect
type: Concept
broader: Astrometry

Automatic patrol telescopes
type: Concept
alternative label: Automated patrol telescopes
broader: Automated telescopes

Phase error
type: Concept
broader: Astrometry

Phase switching
type: Concept
broader: Interferometry

Philosophy of astronomy
type: Concept
broader: Interdisciplinary astronomy

Photodissociation regions
type: Concept
alternative label: PDRs
broader: Molecular clouds
related: Photodissociation reactions
contributor: AAS Frey.Katie Admin
modified: 2022-06-11T22:57:38.308Z

Photoelectric magnitude
type: Concept
broader: Apparent magnitude
contributor: AAS Frey.Katie
definition: The magnitude of an object as measured with a photoelectric photometer.
modified: 2020-11-17T19:26:56.483Z
editorial note: Definition Provenance
  created: 2020-11-17T19:27:06.073Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T19:27:06.098Z

Photoelectric photometry
type: Concept
broader: Photometry
contributor: AAS Frey.Katie
definition: A photometry in which the magnitudes are obtained using a photoelectric photometer.
modified: 2020-11-17T19:27:33.448Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T19:27:42.790Z
modified: 2020-11-17T19:27:42.817Z

Photogrammetry
type: Concept
alternative label: Stereophotogrammetry
broader: Photographic astrometry
broader: Photographic photometry

Photographic astrometry
type: Concept
broader: Astrometry
narrower: Photogrammetry

Photographic magnitude
type: Concept
broader: Apparent magnitude
contributor: AAS Frey.Katie
definition: The apparent magnitude of a star as determined by measuring its brightness on a photographic plate. The photographic magnitude scale is now considered obsolete.
modified: 2020-11-17T19:29:41.014Z
modified: 2020-11-17T19:29:50.914Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:29:50.887Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Photographic photometry
type: Concept
broader: Photometry
narrower: Photogrammetry

Autumnal equinox
type: Concept
broader: Equinox
contributor: AAS Frey.Katie
modified: 2020-11-03T18:36:03.800Z
definition: One of the two points where the ecliptic crosses the celestial equator. At the autumnal equinox the Sun appears to be moving across the equator from the northern celestial hemisphere to the southern celestial hemisphere. The instant of the event.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:36:17.450Z
modified: 2020-11-03T18:36:17.481Z

Photoheliographs
type: Concept
broader: Early astronomical instruments

Photometric parallax
type: Concept
broader: Parallax
contributor: AAS Frey.Katie
definition: A method of deriving the distance of a star using its apparent magnitude and the absolute magnitude inferred from its spectral type.
modified: 2020-11-17T19:31:29.247Z
modified: 2020-11-17T19:31:39.044Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:31:39.006Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Photometric standard stars
type: Concept
broader: Photometry
broader: Standard stars

Photometric systems
type: Concept
broader: Photometry
narrower: Medium band photometry
narrower: Multi-color photometry
narrower: Narrow band photometry
narrower: Broad band photometry
narrower: Color equation
alternative label: Magnitude systems
contributor: AAS Frey.Katie
related: Magnitude
modified: 2020-10-21T18:27:56.957Z

Photometry
type: Concept
broader: Astronomical techniques
narrower: Photoelectric photometry
narrower: Photographic photometry
narrower: Photometric standard stars
narrower: Photometric systems
narrower: Spectrophotometry
narrower: Stellar photometry
narrower: Surface photometry
narrower: Two-color diagrams
narrower: Waveband photometry
narrower: CCD photometry
narrower: Galaxy photometry
narrower: Light curves
narrower: Transit photometry
narrower: Spectral energy distribution
contributor: AAS Frey.Katie
definition: In astronomy, the measurement of the light of astronomical objects, generally in the visible or infrared bands, in which a wavelength band is normally specified.
modified: 2020-11-17T19:32:27.638Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T19:32:37.703Z
modified: 2020-11-17T19:32:37.730Z

Photon decoupling
type: Concept
broader: Big Bang theory
broader: Early universe

Photon sphere
type: Concept
broader: Black hole physics
modified: 2020-11-17T19:33:55.212Z
contributor: AAS Frey.Katie
definition: A surface where if a photon is emitted from one of its points the photon follows a closed orbit and returns periodically to its departure point. Such a surface exists only near sufficiently compact objects where the curvature of space-time is very important. In other words, a body can take a stable orbit around a black hole provided that it moves with the speed of light. However, only photons can have such a velocity; hence the term 'photon sphere.' For a non-rotating Schwarzschild black hole, the photon sphere has a radius of R = 3GM/c2 = 3 RS/2, where G is the gravitational constant, M is the mass, c is the speed of light, and RS is the Schwarzschild radius. For a rotating, Kerr black hole, the situation is much more complex due to the Lense-Thirring effect. In that case circular paths exist for radii whose values depend on the rotation direction. More specifically, in the equatorial plane there are two possible circular light paths: a smaller one in the direction of the rotation, and a larger one in the opposite direction.
editorial note: Definition Provenance
  created: 2020-11-17T19:34:04.907Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T19:34:04.939Z

Photovisual magnitude
type: Concept
broader: Apparent magnitude
contributor: AAS Frey.Katie
definition: Magnitude defined for the combination of a photographic plate and a yellow filter, approximating the spectral sensitivity of the eye.
modified: 2020-11-17T19:34:32.633Z
modified: 2020-11-17T19:34:42.314Z
editorial note: Definition Provenance
  created: 2020-11-17T19:34:42.285Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Pickup ions
type: Concept
alternative label: Pick-up ions
broader: Interplanetary physics

Azimuth
type: Concept
alternative label: Bearing
broader: Horizontal coordinate system
related: Alt-azimuth mounts
contributor: AAS Frey.Katie
definition: The angular distance from the North point eastward to the intersection of the horizon with the vertical circle passing through the object. Azimuth is 0° for an object due north, 90° due east, 180° due south, and 270° due west. Altitude and azimuth constitute the horizon coordinate system.
modified: 2020-11-03T18:37:16.027Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:37:31.259Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:37:31.282Z

Plages
type: Concept
broader: Solar chromosphere
definition: A bright cloud-like feature that appears in the vicinity of a sunspot. Plages represent regions of higher temperature and density within the chromosphere. They are particularly visible when photographed through filters passing the spectral light of hydrogen or calcium.
modified: 2020-11-03T20:24:03.807Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:24:18.014Z
editorial note: Definition Provenance
  created: 2020-11-03T20:24:17.985Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Planet formation
type: Concept
broader: Planetary system formation
related: Protoplanetary disks

Planet hosting stars
type: Concept
broader: Exoplanet astronomy
narrower: Habitable zone

Planetary alignment
type: Concept
broader: Planetary science

Planetary atmospheres
type: Concept
broader: Planetary science
narrower: Atmospheric tides
narrower: Planetary boundary layers
narrower: Scale height
narrower: Upper atmosphere
narrower: Water vapor
narrower: Earth atmosphere
related: Astrophysical masers
related: Exoplanet atmospheres
narrower: Atmospheric variability
narrower: Atmospheric composition
narrower: Atmospheric clouds
related: Planetary climates
contributor: AAS Frey.Katie Admin
narrower: Planetary ionospheres
narrower: Lightning
related: Atmospheric science
modified: 2020-12-11T18:31:08.727Z
narrower: Atmospheric dynamics
narrower: Atmospheric evolution
narrower: Atmospheric structure

Planetary boundary layers
type: Concept
broader: Planetary atmospheres

Planetary cores
type: Concept
broader: Planetary structure

Planetary interior
type: Concept
broader: Planetary structure

Planetary nebulae
type: Concept
broader: Emission nebulae
narrower: Planetary nebulae nuclei
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:19:28.596Z

Planetary nebulae nuclei
type: Concept
alternative label: Nuclei of planetary nebulae
alternative label: Nucleus of planetary nebula
alternative label: Planetary nebula nuclei
broader: Planetary nebulae

Planetary polar regions
type: Concept
broader: Planetary structure

Planetary probes
type: Concept
broader: Space probes

Planetary ring divisions
type: Concept
alternative label: Cassini ring division
alternative label: Cassini's Division
alternative label: Saturn ring division
broader: Planetary rings

Planetary rings
type: Concept
alternative label: Circumplanetary dust
alternative label: Circumplanetary matter
broader: Solar system
narrower: Planetary ring divisions
narrower: Shepherd satellites
narrower: Spokes
narrower: Ansae
alternative label: Circumplanetary medium
contributor: AAS Frey.Katie Admin
narrower: Ring resonance
related: Exoplanet rings
modified: 2022-06-21T17:43:27.480Z

Planetary science
type: Concept
alternative label: Planetology
broader: Solar system astronomy
narrower: Atmospheric science
narrower: Planetary alignment
narrower: Planetary atmospheres
narrower: Planetary structure
narrower: Planetary system formation
narrower: Planetary theory
narrower: Natural satellite formation
narrower: Solar-planetary interactions
narrower: Surface gravity
narrower: Interplanetary magnetic fields
narrower: Interplanetary physics
narrower: Planetary magnetospheres
narrower: Planetary dynamics
definition: The branch of astronomy that deals with the science of planets, or planetary systems, and the solar system.
narrower: Planetary climates
related: Remote sensing
contributor: AAS Frey.Katie Admin
narrower: Comet origins
narrower: Planetary-disk interactions
narrower: Planetary migration
narrower: Natural satellite surfaces
narrower: Asteroid dynamics
narrower: Comet dynamics
narrower: Natural satellite dynamics
narrower: Natural satellite atmospheres
narrower: Collisional processes
narrower: Planetary system evolution
narrower: Natural satellite evolution
narrower: Planetary thermal histories
modified: 2022-06-21T17:54:09.433Z
narrower: Albedo
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T19:35:34.204Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T19:35:34.233Z

Planetary structure
type: Concept
broader: Planetary science
narrower: Mantle
narrower: Oblateness
narrower: Planetary cores
narrower: Planetary interior
narrower: Planetary polar regions
narrower: Polar caps
narrower: Volcanoes
narrower: Hydrosphere
narrower: Lithosphere
contributor: AAS Frey.Katie Admin
scope note: Refers to planets in our Solar system.
related: Exoplanet structure
narrower: Planetary surfaces
modified: 2020-11-12T19:48:07.722Z
narrower: Planetary geology
narrower: Glaciers

Planetary system formation
type: Concept
broader: Planetary science
narrower: Planet formation
narrower: Protoplanetary disks
narrower: Solar system formation

Planetary theory
type: Concept
broader: Planetary science

Planetesimals
type: Concept
broader: Protoplanetary disks
broader: Debris disks

Solar system planets
type: Concept
alternative label: Planets
broader: Solar system
narrower: Solar system gas giant planets
narrower: Solar system terrestrial planets
alternative label: Planets (Solar system)
related: Exoplanets
related: Natural satellites (Solar system)
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T17:44:41.762Z

Plasma clouds
type: Concept
broader: Interstellar clouds

Plasma jets
type: Concept
broader: Stellar mass loss
broader: Jets

Plasmapause
type: Concept
broader: Planetary magnetospheres
contributor: AAS Frey.Katie
definition: The sharp outer boundary of the plasmasphere, at which the plasma density decreases by a factor of 100 or more.
modified: 2020-11-17T19:36:40.468Z
modified: 2020-11-17T19:36:50.077Z
editorial note: Definition Provenance
  created: 2020-11-17T19:36:50.050Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Plate tectonics
type: Concept
alternative label: Continental drift
related: Exoplanet plate tectonics
broader: Tectonics
definition: The theory supported by a wide range of evidence in which the Earth's crust is composed of several large, thin, relatively rigid plates that move relative to one another. The interaction of the plates at their boundaries causes seismic and tectonic activity along these boundaries.
contributor: AAS Frey.Katie
modified: 2020-11-17T19:37:17.318Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:37:26.922Z
  creator: AAS Frey.Katie
modified: 2020-11-17T19:37:26.956Z

Plutinos
type: Concept
broader: Resonant Kuiper belt objects
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:30:23.780Z

Pluto
type: Concept
broader: Dwarf planets
definition: A dwarf planet in the solar system which until 2006 was known as the 9th major planet. Pluto revolves around the Sun in a highly elliptical orbit at a mean distance of 39.5 astronomical units once every about 248 years. The orbit eccentricity is 0.25 (compare with the Earth's 0.02) yielding a perihelion distance of 29.66 astronomical units and an aphelion distance of 48.87 AU. Its orbital inclination is 17 degrees, which is much higher than those of the other planets. Pluto's mass is 1.308 x 10^22 kg, that is 0.00218 Earth mass (0.177 Moon mass), its equatorial radius is 0.19 Earth radius, and its rotation period is equal to 6.39 Earth days. It has five known satellites, in order of distance from Pluto: Charon, Styx, Nix, Kerberos, and Hydra. Pluto's radius is estimated to be about 1150 km (0.18 Earths). Pluto is smaller than seven of the solar system's satellites (the Moon, Io, Europa, Ganymede, Callisto, Titan, and Triton). Pluto's surface has an estimated temperature of 37.5 K and is composed of more than 98% nitrogen ice, with traces of methane and carbon monoxide.
contributor: AAS Frey.Katie Admin
alternative label: (134340) Pluto
alternative label: 134340 Pluto
modified: 2020-12-02T21:43:12.995Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:45:15.117Z
  creator: AAS Frey.Katie
modified: 2020-11-17T19:45:15.147Z
contributor: AAS Frey.Katie

Plutoids
type: Concept
broader: Trans-Neptunian objects
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T03:10:41.521Z

Pogson scale
type: Concept
alternative label: Pogson's scale
broader: Apparent magnitude

Pointing accuracy
type: Concept
broader: Astronomical techniques
narrower: Pointing error

Pointing error
type: Concept
broader: Pointing accuracy

Polar caps
type: Concept
alternative label: Polar ice caps
alternative label: Polar icecaps
broader: Planetary structure
definition: Either of the regions around the poles of a planet.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T20:15:45.862Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T20:16:26.288Z
modified: 2020-11-05T20:16:26.327Z

Polar jets
type: Concept
broader: Radio jets

Polar tides
type: Concept
alternative label: Antarctic barotroclinic tides
alternative label: Antarctic barotropic tides
alternative label: Antarctic tides
alternative label: Arctic barotroclinic tides
alternative label: Arctic barotropic tides
alternative label: Arctic tides
broader: Ocean tides

Polarimeters
type: Concept
alternative label: Polarimetric instrumentation
alternative label: Polarimetric instruments
broader: Astronomical instrumentation

Polarimetry
type: Concept
broader: Astronomical techniques
narrower: Spectropolarimetry
broader: Exoplanet detection methods
definition: The measurement of the polarization state of light, usually through the use of a polarimeter.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:17:01.975Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:48:20.368Z
modified: 2020-11-17T19:48:20.393Z

Polycyclic aromatic hydrocarbons
type: Concept
broader: Interstellar dust
alternative label: Polyaromatic hydrocarbons
alternative label: PAHs
broader: Astrochemistry
alternative label: Polynuclear aromatic hydrocarbons
contributor: AAS Frey.Katie Admin
broader: Molecular physics
modified: 2022-06-11T21:57:01.215Z

Polytropes
type: Concept
alternative label: Polytropic solutions
alternative label: Polytropic stars
broader: Stellar structures

Population I stars
type: Concept
broader: Stellar populations
alternative label: Population 1 stars
alternative label: Pop I
alternative label: Population one stars
scope note: Young, metal-rich stars commonly found in the spiral arms of the Milky Way galaxy
definition: A member of a class of relatively young stars, containing a large fraction of metals, found mainly in the disk of the Galaxy.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:28:01.041Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:28:15.935Z
modified: 2020-11-03T20:28:15.966Z

Population II stars
alternative label: Pop II
type: Concept
broader: Stellar populations
narrower: Population II Cepheid variable stars
alternative label: Population 2 stars
alternative label: Population two stars
definition: A member of a population of relatively old stars, containing a small fraction of metals, found mainly in the halo of the Galaxy and in globular clusters.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:02:18.945Z
modified: 2020-11-03T20:28:46.299Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:28:46.268Z
  creator: AAS Frey.Katie Admin

Population III stars
type: Concept
alternative label: First stars
alternative label: Metal free stars
broader: Stellar populations
alternative label: Population 3 stars
alternative label: Pop III
alternative label: Population three stars
scope note: Hypothetical population of extremely massive and hot stars with virtually no metals.
definition: A member of the first generation of stars, formed out of pristine gas, enriched by primordial nucleosynthesis alone. The material from which these stars formed consisted mostly of hydrogen and helium. Because neutral hydrogen clouds were free of dust, their cooling mechanism was drastically ineffective. As a result, these star forming clouds had a much higher temperature than in the present epoch, and their Jeans mass was much higher. Therefore, these first generation of stars were principally massive, with a typical mass scale of order of about 100 M_sun. Population III stars started forming about 300 million years after the Big Bang at redshifts between 50 and 6, when the Universe had between 1 and 5% of its present age. These stars were probably responsible for the reionization of the Universe. Given their high mass, they lived only a few million years ending with either a pair-instability supernova phase or a direct collapse to a black hole. Population III stars thus initiated the chemical enrichment of the Universe and opened the way to more normal modes of star formation, namely Population II. Some models predict a bimodal initial mass function for the first stars, allowing also for solar mass stars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:29:35.887Z
modified: 2020-11-03T20:29:53.290Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:29:53.262Z

Position angle
type: Concept
broader: Orbital elements
related: Proper motions
contributor: AAS Frey.Katie
definition: The convention for measuring angles on the sky in astronomy (abbreviated as PA). It is the direction of an imaginary arrow in the sky, measured from north through east: 0° = north, 90° = east, 180° = south, and so on to 359° and back to 0°. Applied to a binary system it is the direction of a secondary body or feature from a primary, measured in the system.
modified: 2020-11-17T19:49:45.408Z
modified: 2020-11-17T19:49:54.731Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T19:49:54.705Z

Post-asymptotic giant branch
type: Concept
alternative label: Post-AGB
broader: Hertzsprung Russell diagram
related: Post-asymptotic giant branch stars
contributor: AAS Frey.Katie
modified: 2019-12-02T21:00:13.799Z

pp waves
type: Concept
alternative label: pp-wave
alternative label: pp-wave spacetimes
broader: Gravitational waves

Pre-main sequence stars
type: Concept
alternative label: PMS objects
alternative label: PMS stars
alternative label: Pre main sequence objects
alternative label: Pre-main sequence objects
related: Pre-main sequence
related: Young stellar objects
broader: Stellar evolutionary types
contributor: AAS Frey.Katie
definition: A star that evolves in the Hayashi phase and has not yet reached the zero-age main sequence.
modified: 2020-11-17T19:50:37.850Z
editorial note: Definition Provenance
  created: 2020-11-17T19:50:47.748Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T19:50:47.788Z

Pre-solar nebulae
type: Concept
alternative label: Presolar nebula
broader: Nebulae

Primordial black holes
type: Concept
broader: Astrophysical black holes
definition: A black hole formed following the Big Bang event due to incredibly violent turbulence that squeezed concentrations of matter to high densities. These black holes, first suggested by Stephen Hawking, are expected to have a mass comparable to that of a mountain and a size as small as an atom.
contributor: AAS Frey.Katie Admin
alternative label: Mini black hole
modified: 2020-11-03T20:34:12.758Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:34:25.406Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T20:34:25.439Z

Primordial galaxies
type: Concept
broader: Early universe
broader: Galaxies
definition: A high redshift, metal-deficient galaxy that formed very early in the history of the Universe.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:34:58.401Z
modified: 2020-11-03T20:35:10.568Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:35:10.538Z
  creator: AAS Frey.Katie Admin

Primordial magnetic fields
type: Concept
broader: Magnetic fields

Proper motions
type: Concept
alternative label: Stellar spatial motions
broader: Stellar motion
related: Position angle
related: Time domain astronomy
definition: The apparent motion of a star across the sky (not including a star's parallax), arising from the star's velocity through space with respect to the Sun. Proper motion is usually tabulated in star catalogs as changes in right ascension and declination per year or century.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:35:46.612Z
modified: 2020-11-03T20:36:00.383Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:36:00.348Z
  creator: AAS Frey.Katie Admin

Protogalaxies
type: Concept
broader: Galaxies
related: Cosmology
definition: A huge mass of gas that by contraction and condensation becomes a galaxy of stars. A galaxy during the early phase, before it has developed its present shape and stellar/gas content.
modified: 2020-11-03T20:37:32.074Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T20:37:44.061Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T20:37:44.088Z

Proton-proton reaction
type: Concept
alternative label: Proton proton cycle
alternative label: Proton proton reaction
alternative label: Proton-proton cycle
broader: Hydrogen burning
contributor: AAS Frey.Katie
modified: 2020-11-17T19:54:41.701Z
definition: A thermonuclear reaction in which two protons collide at very high velocities and combine to form a deuterium.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T19:54:52.833Z
modified: 2020-11-17T19:54:52.864Z

B supergiant stars
contributor: AAS Frey.Katie
type: Concept
alternative label: B supergiants
broader: B stars
broader: Early-type supergiant stars
alternative label: B-type supergiant stars
alternative label: B-type supergiants
related: Alpha Cygni variable stars
modified: 2019-12-02T21:24:15.749Z

Protoplanetary disks
type: Concept
broader: Planetary system formation
broader: Circumstellar disks
broader: Interplanetary medium
narrower: Planetesimals
related: Planet formation
narrower: Proplyds
broader: Protostars
scope note: Used for both the Solar systems historic protoplanetary disk and for protoplanetary disks external to the Solar system.
alternative label: Protoplanetary disks (Extrasolar)
definition: A circumstellar disk of gas and dust surrounding a pre-main sequence star from which planetary systems form. Protoplanetary disks are remnants of accretion disks which bring forth stars. Typically, their sizes are ~100-500 AU, masses ~10^-2 solar masses, lifetimes ~10^6 - 10^7 years, and accretion rates ~10^-7 - 10^-8 solar masses per year. According to the standard theory of planet formation, called core accretion, planets come into being by the growth of dust grains which stick together and produce ever larger bodies, known as planetesimals. The agglomeration of these planetesimals of 100 to 1000 km in size into rocky Earth-mass planets is the main outcome of this theory. Beyond the snow line in the disk, if the masses of these cores of rock and ice grow higher than 10 times that of Earth in less than a few million years, gas can rapidly accrete and give rise to giant gaseous planets similar to Jupiter. If core building goes on too slowly, the disk gas dissipates before the formation of giant planets can start. Finally the left-over planetesimals that could not agglomerate into rocky planets or core of giant planets remain as a debris disk around the central object that has become a main sequence star. An alternative to core accretion theory is formation of planets in a massive protoplanetary disk by gravitational instabilities. The validity of these two theories is presently debated.
modified: 2020-11-03T20:39:09.227Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:39:21.751Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T20:39:21.783Z

Protoplanetary nebulae
type: Concept
alternative label: Preplanetary nebulae
alternative label: Protoplanetary nebula
broader: Nebulae
definition: A short-lived transition object between the asymptotic giant branch (AGB) and planetary nebula phases.
contributor: AAS Frey.Katie Admin
alternative label: PPN
modified: 2020-11-03T20:40:11.636Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:40:04.850Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T20:40:04.875Z

Protostars
type: Concept
broader: Stellar types
broader: Interstellar medium
narrower: Bok globules
narrower: Young stellar objects
narrower: Cocoon stars
narrower: Cometary nebulae
contributor: AAS Frey.Katie Admin
narrower: Protoplanetary disks
definition: A stage in the process of star formation, after the gravitational collapse of the dense pre-stellar core and before the initiation of nuclear fusion in the central object which will eventually become a star. Protostars are classified into four groups: Class 0, Class I, Class II, and Class III.
modified: 2020-11-03T20:40:42.900Z
modified: 2020-11-03T20:40:56.141Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:40:56.112Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Ptolemy stones
type: Concept
broader: Early astronomical instruments

Pulsar planets
type: Concept
broader: Exoplanets
definition: A planet orbiting a pulsar. The first such planet to be discovered was around a millisecond pulsar known as PSR 1257+12.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:42:19.600Z
modified: 2020-11-03T20:42:34.464Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:42:34.430Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Pulsar timing method
type: Concept
broader: Timing variation methods

Pulsars
type: Concept
broader: Neutron stars
narrower: Millisecond pulsars
narrower: Optical pulsars
narrower: Radio pulsars
narrower: Rotation powered pulsars
narrower: Binary pulsars
definition: A rotating neutron star that emits a radio beam that is centered on the magnetic axis of the neutron star. As the magnetic axis and hence the beam are inclined to the rotation axis, a pulse is seen every time the rotation brings the magnetic pole region of the neutron star into view. In this way the pulsar acts much as a light house does, sweeping a beam of radiation through space. The pulse or spin periods range from 1.4 milliseconds to 8.5 seconds. As neutron stars concentrate an average of 1.4 solar masses on a diameter of only 20 km, pulsars are exceedingly dense and compact, representing the densest matter in the observable Universe. The pulsar radiation, chiefly emitted in radio frequencies (0.1-1 GHz), is highly polarized. The exact mechanism by which a pulsar radiates is still a matter of vigorous investigation. Simply put, an enormous electric field is induced by the rotation of a magnetized neutron star. The force of this field exceeds gravity by ten to twelve orders of magnitudes. Charged particles are whereby pulled out from the stellar surface resulting in a dense, magnetized plasma that surrounds the pulsar (magnetosphere). The charged particles flow out of the magnetic polar caps of the neutron star, following the open magnetic field lines. The acceleration of the charged particles along the curved magnetic field lines will cause them to radiate.
related: Pulsar wind nebulae
contributor: AAS Frey.Katie
modified: 2022-01-03T15:01:46.847Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:44:06.340Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:44:06.304Z

Pulsating variable stars
type: Concept
broader: Intrinsic variable stars
narrower: Mira variable stars
narrower: Multi-periodic variable stars
narrower: PV Telescopii variable stars
narrower: Beta Cephei variable stars
narrower: 53 Persei stars
narrower: Cepheid variable stars
narrower: Delta Delphini variable stars
narrower: Delta Scuti variable stars
narrower: Double-mode variable stars
narrower: Irregular variable stars
narrower: Lambda Eridani stars
narrower: Long period variable stars
contributor: AAS Frey.Katie Admin
narrower: RR Lyrae variable stars
narrower: Gamma Doradus variable stars
narrower: Blue large-amplitude pulsators
narrower: Alpha Cygni variable stars
alternative label: Pulsating stars
definition: A type of variable star that changes its brightness by changing its volume through expansion and contraction. Classical pulsating stars, including Cepheids, RR Lyrae, and Delta Scuti variables, are located in a quite narrow almost vertical region in the H-R diagram, known as instability strip.
modified: 2020-12-16T19:12:58.529Z
modified: 2020-11-03T20:45:55.116Z
editorial note: Definition Provenance
  created: 2020-11-03T20:45:55.087Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Pulsation frequency method
type: Concept
broader: Timing variation methods

Pulsation modes
type: Concept
broader: Stellar pulsations
definition: The way in which pulsations occur in a star due to the fact that stars act as resonant cavities, as studied in asteroseismology. A star may pulsate either with approximately spherical symmetry (radial pulsation), or as a series of waves running across the surface (non-radial pulsation). Pulsation may occur in a single mode or in multiple modes, depending on the type of star. Three different modes of pulsations have been detected through the helioseismology of the Sun: p mode, g mode, and f mode, generated by acoustic, gravity, and surface gravity waves respectively.
modified: 2020-11-03T20:46:46.623Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T20:47:01.449Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T20:47:01.486Z

Baade-Wesselink method
type: Concept
alternative label: Baade Wesselink method
alternative label: Expanding photosphere method
alternative label: Expanding-photosphere method
broader: Astrometry
contributor: AAS Frey.Katie
definition: A method used to determine the size of certain types of pulsating stars, including Cepheids, from their magnitude variations (photometry) and the corresponding radial velocities (spectroscopy).
modified: 2020-11-03T18:39:56.429Z
modified: 2020-11-03T18:40:10.954Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:40:10.929Z

Purkinje effect
type: Concept
alternative label: Purkinje shift
broader: Amateur astronomy
related: Variable stars
contributor: AAS Frey.Katie
definition: The increasing sensibility of the retina for light of shorter wavelength as the brightness decreases. In those conditions red objects are perceived to fade faster than blue objects of the same brightness.
modified: 2020-11-17T19:57:51.295Z
modified: 2020-11-17T19:58:02.164Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T19:58:02.132Z

Quadrants
type: Concept
broader: Galactic coordinate system

Quantum cosmology
type: Concept
broader: Cosmology

Quantum gravity
type: Concept
broader: Non-standard theories of gravity
narrower: Gravastars
contributor: AAS Frey.Katie
definition: A theory of gravity, yet to be developed, that would properly include quantum mechanics. Because of the tensor nature of general relativity, it is not renormalizable as a field theory in perturbation from flat space. So far various attempts to quantize general relativity have been unsuccessful.
modified: 2020-11-17T19:58:30.395Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T19:58:42.025Z
modified: 2020-11-17T19:58:42.057Z

Quasar-galaxy pairs
type: Concept
broader: Quasars
broader: Galaxies

Quasar absorption line spectroscopy
type: Concept
broader: Intergalactic medium

Quasar microlensing
type: Concept
broader: Gravitational microlensing

Quasars
type: Concept
alternative label: QSO
alternative label: Quasi-stellar galaxies
alternative label: Quasi-stellar object
alternative label: Quasi-stellar radio sources
broader: Active galactic nuclei
broader: Supermassive black holes
narrower: Quasar-galaxy pairs
narrower: Radio loud quasars
narrower: Radio quiet quasars
narrower: X-ray quasars
narrower: Broad-absorption line quasar
narrower: Double quasars
related: Radio sources
contributor: AAS Frey.Katie Admin
definition: An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100 times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
modified: 2020-12-16T19:20:23.826Z
editorial note: Definition Provenance
  created: 2020-11-03T21:01:18.869Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T21:01:18.903Z

Quasinormal modes
type: Concept
broader: Black hole physics

Quiet sun
type: Concept
broader: Solar cycle
related: Quiescent solar prominence
contributor: AAS Frey.Katie
related: Active sun
definition: The Sun when the 11-year cycle of solar activity is at a minimum.
modified: 2020-11-17T20:00:10.084Z
modified: 2020-11-17T20:00:18.958Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T20:00:18.926Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Quintessence
type: Concept
broader: Dark energy
definition: In cosmology, a hypothetical new 'element,' distinct from any normal matter (either baryonic or not) or radiation, intended to explain the observed ever accelerating expansion of the Universe. Quintessence can have several types and differs from the cosmological constant in that it can vary in space and time. In modern physics, the four known "elements" are the baryons (proton, neutron, etc.), the leptons (neutrinos, electrons, etc.), the photon, and the hypothetical non-baryonic matter, which is thought to be 80% of the total matter in the Universe. The quintessence field is a possibility which can be confirmed or disproved by measurements of the dark energy value at different redshifts. In some models, the quintessence is fine-tuned to explain both the cosmological constant problem and the inflation in the very early Universe.
modified: 2020-12-17T16:11:17.416Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-17T20:01:09.025Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T20:01:08.993Z
contributor: AAS Frey.Katie

R-process
type: Concept
broader: Nucleosynthesis
contributor: AAS Frey.Katie
definition: A nucleosynthesis process in which chemical elements heavier than zinc are created through the intense bombardment of other elements by neutrons in rapid succession. The essential feature of the r-process is the release of great numbers of neutrons in a very short time (less than 100 seconds). The r-process is a 'rapid' version of the s-process, occurring in supernova core collapse and possibly when a neutron star merges with a black hole in a binary star.
modified: 2020-11-17T20:02:31.156Z
modified: 2020-11-17T20:02:42.550Z
editorial note: Definition Provenance
  created: 2020-11-17T20:02:42.519Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

R associations
type: Concept
alternative label: R-association
broader: Stellar associations
related: Reflection nebulae
definition: A stellar association containing a number of reflection nebulae. The stars are of low or intermediate mass and young, less than a million years old. They are still surrounded by patches of dust that reflect and absorb light from the interstellar cloud in which they formed. This type of association was first suggested by Sidney van den Bergh.
modified: 2020-11-05T20:27:39.924Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T20:27:55.154Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-05T20:27:55.187Z

R Coronae Borealis variable stars
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: R Coronae Borealis
alternative label: R Coronae Borealis stars
alternative label: R Coronae Borealis variables
alternative label: R c b stars
alternative label: R cor bor stars
alternative label: R-Coronae Borealis variables
broader: Flare stars
broader: Irregular variable stars
modified: 2020-12-16T15:47:45.708Z

Radar astronomy
type: Concept
broader: Astronomical methods
narrower: Radar observations
definition: Astronomy in which celestial bodies in the solar system are studied by analyzing the return of radio waves directed at them.
contributor: AAS Frey.Katie
modified: 2024-06-20T12:30:07.657Z
modified: 2024-06-20T12:30:50.071Z
editorial note: Definition Provenance
  created: 2024-06-20T12:30:50.064Z
  comment: Merriam-Webster Dictionary
  creator: AAS Frey.Katie

Baily's beads
type: Concept
alternative label: Bailys beads
broader: Eclipses
contributor: AAS Frey.Katie
definition: A phenomenon that occurs during a total eclipse of the Sun. Just prior to and after totality, sunlight shines through the lunar valleys on the Moon's limb, causing the dark face of the Moon to appear to be surrounded by a shining 'necklace of pearls'.
modified: 2020-11-03T18:40:41.782Z
modified: 2020-11-03T18:40:51.437Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:40:51.403Z

Radar telescopes
type: Concept
broader: Radio telescopes

Radial pulsations
type: Concept
broader: Stellar pulsations

Radial velocity
type: Concept
alternative label: Astrometric radial velocity
alternative label: Radial-velocity method
alternative label: Spectroscopic radial velocity
broader: Astrometry
alternative label: Radial velocity methods
broader: Exoplanet detection methods
definition: The component of a three-dimensional velocity vector of an object directed along the line of sight. It is measured by examining the Doppler shift of lines in the spectrum of astronomical objects.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:17:57.273Z
editorial note: Definition Provenance
  created: 2020-11-17T20:03:19.797Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie
modified: 2020-11-17T20:03:19.834Z

Radiative braking
type: Concept
broader: Stellar rotation
contributor: AAS Frey.Katie
definition: The slowing down of a star's rotation due to radiative momentum transfer caused by emission of electromagnetic radiation.
modified: 2020-11-17T20:03:56.971Z
editorial note: Definition Provenance
  created: 2020-11-17T20:04:06.904Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T20:04:06.932Z

Radiative transfer
type: Concept
broader: Cosmology
related: Radiative transfer equation
contributor: AAS Frey.Katie
definition: The process by which the electromagnetic radiation passes through a medium that may contain any combination of scatterers, absorbers, and emitters.
modified: 2020-11-17T20:05:16.250Z
modified: 2020-11-17T20:05:26.074Z
editorial note: Definition Provenance
  created: 2020-11-17T20:05:26.044Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Radiative transfer equation
type: Concept
broader: Analytical mathematics
related: Radiative transfer
definition: The equation that describes the radiative transfer. It states that the specific intensity of radiation during its propagation in a medium is subject to losses due to extinction and to gains due to emission.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:41:07.724Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-17T20:06:37.706Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T20:06:37.739Z

Radio astrometry
type: Concept
broader: Radio astronomy
broader: Astrometry

Radio astronomy
type: Concept
broader: Astronomical methods
narrower: Millimeter astronomy
narrower: Radio astrometry
narrower: Spectral index
narrower: Submillimeter astronomy
narrower: Sunyaev-Zeldovich effect
narrower: Brightness temperature
narrower: Cosmic noise
narrower: Interplanetary scintillation
narrower: Interstellar scintillation
related: Radio sources
contributor: AAS Frey.Katie
related: Radio spectroscopy
definition: The branch of astronomy that deals with the study of the Universe by means of radio waves. Radio waves are the electromagnetic radiation with the longest wavelengths (and lowest energies), ranging from 0.3 mm to several km. Radio waves form a very broad category, which includes the submillimeter waves (with a wavelengths of 0.3-1 mm) and microwave regions (1mm to several cm).
modified: 2024-06-20T12:28:18.383Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:08:53.728Z
editorial note: Definition Provenance
  created: 2024-06-20T12:28:36.539Z
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2024-06-20T12:28:36.545Z

Radio bursts
type: Concept
broader: Burst astrophysics
broader: Radio sources
related: Radio transient sources
definition: A burst of emission in the radio frequencies of the electromagnetic spectrum.
modified: 2020-11-03T21:07:08.735Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:07:20.012Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:07:20.040Z

Baker-Nunn cameras
type: Concept
broader: Wide-field telescopes
broader: Catadioptric telescopes

Radio continuum emission
type: Concept
alternative label: Radio continuum
broader: Radio sources
broader: Interstellar emissions
definition: A continuum emission with frequencies in the radio range of the electromagnetic spectrum.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:53:10.932Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:09:50.730Z
modified: 2020-11-17T20:09:50.759Z

Radio cores
type: Concept
broader: Active galactic nuclei
broader: Galaxy structure
related: Radio sources

Radio galaxies
type: Concept
broader: Active galaxies
narrower: Tailed radio galaxies
narrower: Fanaroff-Riley radio galaxies
narrower: Giant radio galaxies
related: Radio sources
definition: A galaxy that is extremely luminous at radio wavelengths between 10 MHz and 100 GHz. The radio luminosity of a strong radio galaxy (10^37 - 10^39 watts) can be up to a million times greater than the radio output of an ordinary galaxy and up to a hundred times greater than the optical luminosity of a galaxy such as the Milky Way. The optical counterparts of radio galaxies are usually an elliptical galaxy. Radio galaxies often exhibit jet structure from a compact nucleus. They typically display two radio lobes that are often approximately aligned with the jets observed in the optical and that may extend for millions of light-years.
modified: 2020-11-03T21:08:48.086Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:09:00.606Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:09:00.580Z

Radio hot spots
type: Concept
broader: Active galactic nuclei

Radio interferometers
type: Concept
broader: Radio telescopes
narrower: Very Large Array
narrower: Very long baseline interferometers
narrower: Long baseline interferometers
modified: 2020-11-03T21:09:31.016Z
definition: An interferometer designed for radio frequencies.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:09:44.508Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:09:44.473Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Radio interferometry
type: Concept
broader: Interferometry
narrower: Very long baseline interferometry
scope note: See radio interferometer

Radio jets
type: Concept
broader: Active galactic nuclei
broader: Galaxies
broader: Jets
narrower: Polar jets
narrower: Relativistic jets
definition: An astrophysical jet appearing in the radio wavelengths of the electromagnetic spectrum.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:10:13.910Z
modified: 2020-11-03T21:10:22.624Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:10:22.592Z
  creator: AAS Frey.Katie Admin

Radio lobes
type: Concept
broader: Active galactic nuclei
scope note: Radio source feature
contributor: AAS Frey.Katie Admin
definition: An extended region of diffuse radio emission, often dumbbell shaped, that surrounds a radio galaxy.
modified: 2020-11-03T21:10:39.880Z
modified: 2020-11-03T21:10:52.318Z
editorial note: Definition Provenance
  created: 2020-11-03T21:10:52.288Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Radio loud quasars
type: Concept
alternative label: Radio-loud quasars
broader: Quasars
definition: A quasar that has the same characteristics as a radio-quiet quasar with the addition of having strong radio emissions.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:03:14.190Z
modified: 2020-11-03T21:03:25.967Z
editorial note: Definition Provenance
  created: 2020-11-03T21:03:25.940Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Barium stars
type: Concept
alternative label: Ba II stars
broader: Heavy metal stars
narrower: Semi-barium stars
definition: A type of star, usually G or K giants, whose spectra show unusually strong absorption lines of barium, strontium, and other s-process elements.
modified: 2020-11-04T14:41:59.578Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-04T14:42:12.164Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T14:42:12.192Z

Radio observatories
type: Concept
broader: Observatories

Radio occultation
type: Concept
broader: Occultation

Radio plumes
type: Concept
broader: Active galactic nuclei

Radio pulsars
type: Concept
broader: Pulsars
related: Radio sources
definition: A pulsar that emits pulses in radio waves. The bulk of discovered pulsars are radio pulsars. There is a small number of pulsars that emit at optical wavelengths, X-ray wavelengths, and gamma-ray wavelengths.
modified: 2020-11-03T21:11:22.278Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:11:32.354Z
modified: 2020-11-03T21:11:32.386Z

Radio quiet quasars
type: Concept
alternative label: Radio-quiet quasars
broader: Quasars
definition: A type of quasar with weak radio emission. These types of quasars have strong emissions in both the optical and X-ray spectra. Within the optical spectrum, both broad and narrow emission lines are present. Their host is usually an elliptical galaxy, but less commonly, it might be a spiral.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:03:48.423Z
modified: 2020-11-03T21:03:59.798Z
editorial note: Definition Provenance
  created: 2020-11-03T21:03:59.765Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Radio receivers
type: Concept
broader: Astronomical detectors

Radio source catalogs
type: Concept
alternative label: MICA ICRF Radio Source Catalog
alternative label: RADIO Master Catalog
preferred label: Radio source catalogues
broader: Catalogs
alternative label: Cambridge Catalogue of Radio Sources
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:44:52.126Z

Radio source counts
type: Concept
broader: Surveys
related: Radio sources

Radio sources
type: Concept
alternative label: Radio lines
broader: Astronomical radiation sources
narrower: Radio continuum emission
narrower: Discrete radio sources
narrower: Extragalactic radio sources
narrower: Galactic radio sources
related: Quasars
related: Radio cores
related: Radio galaxies
related: Radio pulsars
related: Radio source counts
narrower: Radio transient sources
related: Active galactic nuclei
narrower: Radio bursts
related: Radio astronomy
definition: A point or small portion of the sky giving stronger radio emission than the sky in its vicinity.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:11:55.428Z
modified: 2020-11-03T21:12:07.533Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:12:07.504Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Radio spectroscopy
type: Concept
broader: Spectroscopy
contributor: AAS Frey.Katie
related: Radio astronomy
modified: 2020-10-21T19:56:09.839Z

Barred spiral galaxies
type: Concept
alternative label: SB galaxies
broader: Spiral galaxies
definition: A spiral galaxy that exhibits a bar-shaped structure in its nucleus.
modified: 2020-10-26T19:05:18.316Z
contributor: AAS Frey.Katie
narrower: Galaxy bars
modified: 2020-10-26T19:05:31.597Z
editorial note: Definition Provenance
  created: 2020-10-26T19:05:31.569Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Radio telescopes
type: Concept
broader: Telescopes
narrower: Radar telescopes
narrower: Radio interferometers
narrower: Radioheliographs
narrower: Single-dish antennas
narrower: Solar radio telescopes
narrower: Heterodyne receivers
definition: A telescope whose receiver is sensitive to radio waves.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:12:36.971Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:12:51.363Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:12:51.403Z

Radioheliographs
type: Concept
broader: Radio telescopes
broader: Solar telescopes

Rapid bursts
type: Concept
broader: Burst astrophysics

Rapid stellar oscillations
type: Concept
alternative label: RoAp oscillations
broader: Stellar oscillations

Recurrent novae
type: Concept
broader: Novae
definition: A cataclysmic variable star that undergoes outbursts similar to those found in novae.
modified: 2020-11-03T21:15:36.383Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:15:49.771Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:15:49.805Z

Red dwarf flare stars
type: Concept
broader: Flare stars
example: Proxima Centauri
modified: 2022-06-24T15:32:08.123Z
contributor: AAS Frey.Katie Admin

Red giant branch
type: Concept
broader: Giant branch
narrower: Red giant bump
narrower: Red giant clump
narrower: Red giant tip
definition: The evolutionary path of a star that has exhausted its available hydrogen content in the core, between the main-sequence turnoff and the helium flash.
contributor: AAS Frey.Katie Admin
related: Red giant stars
modified: 2020-11-03T21:20:17.952Z
editorial note: Definition Provenance
  created: 2020-11-03T21:20:32.427Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:20:32.456Z

Red giant bump
type: Concept
alternative label: Red bump
broader: Red giant branch

Baryogenesis
type: Concept
alternative label: Matter-antimatter asymmetry
broader: Early universe
contributor: AAS Frey.Katie
definition: The hypothetical mechanism of creating the baryon asymmetry in the Universe. Explaining the observed matter asymmetry is an important open question in physical cosmology.
modified: 2020-11-03T18:41:20.043Z
modified: 2020-11-03T18:41:56.428Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:41:56.384Z

Red giant clump
type: Concept
alternative label: Red clump
broader: Red giant branch

Red giant tip
type: Concept
broader: Red giant branch

Red giant stars
type: Concept
alternative label: Red giant branch stars
alternative label: Red giants
broader: Giant stars
narrower: Red straggler stars
related: Cocoon stars
narrower: OGLE small amplitude red giant stars
definition: A certain star of spectral type K or later that occupies the upper right portion of the H-R diagram. Red giants are evolved stars that have exhausted their hydrogen fuel in the core. They may have a luminosity up to 1000 times greater than main sequence stars of the same spectral type. Red giants belong to the luminosity class III or II (bright giants). They are luminous because of their great size, but have a relatively low surface temperature. All normal stars are expected to pass eventually through a red-giant phase as a consequence of stellar evolution. When a main sequence star has converted approximately 10% of its hydrogen to helium, nuclear reactions in the core stop (Schönberg-Chandrasekhar limit). The hydrostatic equilibrium is no longer maintained, and the core contracts while the outer layers expand and cool. This process produces the low surface temperature and large size (from 10 to 100 times that of the Sun) that characterize the red giant. In the core the temperature continues to rise. When it approaches 100,000,000 K helium will begin to fuse into carbon. Prominent bright red giants in the night sky include Aldebaran and Arcturus.
contributor: AAS Frey.Katie Admin
related: Red giant branch
example: Arcturus
modified: 2022-06-24T15:26:04.240Z
modified: 2020-11-03T21:18:56.046Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:18:56.017Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Red sequence galaxies
type: Concept
broader: Galaxy colors

Red supergiant stars
type: Concept
alternative label: Red supergiants
broader: Supergiant stars
related: Cocoon stars
contributor: AAS Frey.Katie Admin
broader: Late-type supergiant stars
related: M supergiant stars
related: K supergiant stars
definition: A supergiant star with spectral type K or M. Red supergiants are the largest stars in the Universe, but not necessarily the most massive. Betelgeuse and Antares are the best known examples of a red supergiant.
example: Betelgeuse
modified: 2022-06-24T15:27:33.408Z
modified: 2020-11-03T21:21:29.081Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:21:29.052Z

Reddened stars
type: Concept
broader: Interstellar extinction
definition: A star whose light has undergone reddening.
modified: 2020-11-03T21:21:57.359Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:22:18.093Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:22:18.061Z

Reddening law
type: Concept
broader: Extinction

Redshift surveys
type: Concept
alternative label: Galaxy redshifts
alternative label: Galaxy surveys
broader: Surveys
related: Redshifted

Redshifted
type: Concept
alternative label: Red shift
alternative label: Redshift
broader: Cosmology
broader: Doppler shift
related: Redshift surveys
related: Cosmic microwave background radiation
definition: A spectral line whose wavelength does not coincide with its theoretical value and is shifted toward longer wavelengths.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:22:53.557Z
editorial note: Definition Provenance
  created: 2020-11-03T21:23:08.259Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:23:08.292Z

Baryon acoustic oscillations
type: Concept
broader: Early universe
alternative label: BAO
contributor: AAS Frey.Katie Admin
definition: In cosmology, one of a series of peaks and troughs that are present in the power spectrum of matter fluctuations after the recombination era, and on large scales. At the time of the Big Bang, and for about 380,000 years afterwards, Universe was ionized and photons and baryons were tightly coupled. Acoustic oscillations arose from perturbations in the primordial plasma due to the competition between gravitational attraction and gas+photons pressure. After the epoch of recombination, these oscillations froze and imprinted their signatures in both the CMB and matter distribution. In the case of the photons, the acoustic mode history is manifested as the high-contrast Doppler peaks in the temperature anisotropies. As for baryons, they were in a similar state, and when mixed with the non-oscillating cold dark matter perturbations, they left a small residual imprint in the clustering of matter on very large scales, ~100 h^-1 Mpc (h being the Hubble constant in units of 100 km s^-1 Mpc^-1). The phenomenon of BAOs, recently discovered using the Sloan Digital Sky Survey data, is a confirmation of the current model of cosmology. Like Type Ia supernovae, BAOs provide a standard candle for determining cosmic distances. The measurement of BAOs is therefore a powerful new technique for probing how dark energy has affected the expansion of the Universe.
modified: 2020-11-06T01:49:09.629Z
modified: 2020-10-26T19:07:17.429Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-10-26T19:07:17.405Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Reflecting telescopes
type: Concept
alternative label: Catoptric telescopes
alternative label: Reflector telescopes
broader: Optical telescopes
narrower: Newtonian telescopes
narrower: Cassegrain telescopes
narrower: Gregorian telescopes
scope note: Refers to optical telescope
definition: A telescope in which the image is produced by reflection of light by a concave mirror.
modified: 2020-11-03T21:26:53.391Z
contributor: AAS Frey.Katie Admin
narrower: Primary mirror
narrower: Secondary mirror
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:27:05.913Z
modified: 2020-11-03T21:27:05.939Z

Reflection nebulae
type: Concept
alternative label: Reflection nebula
broader: Nebulae
contributor: AAS Frey.Katie Admin
related: R associations
definition: A type of nebula that is visible from its reflection of starlight. Bright stars near reflection nebulae emit light into the region that is reflected by the large amount of dust there. The size of the dust grains causes blue light to be reflected more efficiently than red light, so these reflection nebulae frequently appear blue in color.
modified: 2020-11-03T21:27:27.153Z
modified: 2020-11-03T21:27:37.741Z
editorial note: Definition Provenance
  created: 2020-11-03T21:27:37.715Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Refracting telescopes
type: Concept
alternative label: Dioptrics
broader: Optical telescopes
definition: A telescope in which an image is formed by the refraction of light through a lens or lens system.
modified: 2020-11-03T21:28:00.455Z
contributor: AAS Frey.Katie Admin
narrower: Lenses
narrower: Keplerian telescopes
narrower: Galilean telescopes
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:28:14.007Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:28:14.037Z

Reionization
type: Concept
alternative label: Re-ionisation
alternative label: Re-ionization
preferred label: Reionisation
broader: Big Bang theory
broader: Early universe
definition: The ionization of neutral hydrogen atoms formed during recombination epoch in the early Universe.
modified: 2021-09-27T15:43:26.698Z
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-17T20:20:26.313Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T20:20:26.346Z

Reissner-Nordström black holes
type: Concept
alternative label: Reissner Nordstrom black holes
alternative label: Reissner Nordström black holes
broader: Nonrotating black holes
broader: Charged black holes
contributor: AAS Frey.Katie Admin
alternative label: Reissner-Nordstrom black holes
definition: A type of electrically charged black hole that is spherically symmetric and non-rotating. Another type of such objects is the Kerr-Newman black hole.
modified: 2020-11-03T21:28:56.319Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:29:16.390Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T21:29:16.418Z

Relativistic aberration
type: Concept
broader: Special relativity
broader: Astrometry
modified: 2020-11-24T16:39:10.526Z
contributor: AAS Frey.Katie Admin
definition: The aberration of light for an object moving with relativistic speed. In contrast to the classical case, the Lorentz transformation between the rest frame of the observer and that of the object must be used. Relativistic aberration is expressed by the equation: cos φ' = (cos φ - )/(1 - cos φ.v/c), where φ is the classical aberration angle, v the speed of the Earth, and c the speed of light.
contributor: AAS Frey.Katie
modified: 2020-11-17T20:22:48.999Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T20:22:48.965Z

Relativistic binary stars
type: Concept
alternative label: Relativistic binaries
alternative label: Relativistic binary
broader: Relativistic stars
broader: Binary stars
broader: High energy astrophysics

Relativistic cosmology
type: Concept
broader: Cosmology

Relativistic disks
type: Concept
alternative label: Relativistic discs
broader: Active galactic nuclei

Relativistic fluid dynamics
type: Concept
broader: Relativistic mechanics

Baryon density
type: Concept
broader: Density parameters

Relativistic jets
type: Concept
broader: Radio jets

Relativistic mechanics
type: Concept
broader: Relativity
narrower: Relativistic fluid dynamics

Relativistic stars
type: Concept
broader: Neutron stars
narrower: Relativistic binary stars

Relativity
type: Concept
alternative label: Relativistic astrophysics
alternative label: Relativistic models
broader: Astrophysical processes
narrower: Relativistic mechanics
narrower: Special relativity
narrower: General relativity
related: Gravitation

Relaxation time
type: Concept
alternative label: Relaxation (physics)
broader: Astrometry
definition: The characteristic length of time that is required for a system undergoing relaxation to move to its equilibrium state. If the system follows an exponential law G = G_0 exp(-t / τ), the relaxation time is the time required for G to obtain the fraction 1/e of its initial value G_0.
modified: 2020-11-24T16:37:56.685Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T20:23:44.279Z
modified: 2020-11-17T20:23:44.305Z
contributor: AAS Frey.Katie

Remote telescope astrophotography
type: Concept
broader: Astrophotography

Resonant Kuiper belt objects
type: Concept
alternative label: Resonant Kuiper-belt objects
broader: Trans-Neptunian objects
narrower: Plutinos
narrower: Scattered disk objects
narrower: Twotinos

RGB photometry
type: Concept
alternative label: Red-green-blue photometry
broader: Broad band photometry

RGU photometry
type: Concept
broader: Broad band photometry

Right ascension
type: Concept
alternative label: Celestial longitude
broader: Equatorial coordinate system
contributor: AAS Frey.Katie
definition: A coordinate in the equatorial system measured from the vernal equinox eastward to the point where the object hour circle intersects the celestial equator. Right ascension (symbol α) is expressed in hours, minutes, and seconds.
modified: 2020-11-17T20:25:48.204Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:25:58.364Z
modified: 2020-11-17T20:25:58.408Z

Accretion
type: Concept
alternative label: Particle accretion
broader: Newtonian gravitation
narrower: Stellar accretion
narrower: Bondi accretion
narrower: Galaxy accretion
contributor: AAS Frey.Katie
definition: The process by which an object increases its mass under the influence of its gravitational attraction. Accretion plays a key role in a wide range of astrophysical phenomena. In particular stars result from the accretion of material by a protostar from a surrounding molecular cloud. The accumulation of mass on the protostar involves the formation of an accretion disk. Theoretical and observational investigations of protostars and newborn stars indicate the important role of magnetic fields in this process. They favor the magnetospheric accretion model for mass transfer from the circumstellar disk onto the newborn star. In this model, the stellar magnetosphere truncates the disk at a few stellar radii. Gas from the disk accretes onto the star along the magnetic field lines and hits the stellar surface at approximately the free fall velocity, causing a strong accretion shock. Various emission lines are formed in the infalling magnetospheric flow. Moreover, optical/ultraviolet excess continuum emission is produced in the accretion shocks. The accretion is accompanied by mass ejection through collimated bipolar jets.
modified: 2020-11-03T17:43:10.683Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T17:43:25.638Z
modified: 2020-11-03T17:43:25.668Z

Baryonic dark matter
type: Concept
broader: Dark matter
contributor: AAS Frey.Katie
definition: Dark matter made up of baryons that are not luminous enough to produce any detectable radiation. It is generally believed that most dark matter is non-baryonic. The baryonic dark matter could reside in a number of forms, including cold gas and compact objects.
modified: 2020-11-03T18:43:11.923Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:43:26.316Z
  creator: AAS Frey.Katie
modified: 2020-11-03T18:43:26.351Z

Ring galaxies
type: Concept
broader: Disk galaxies
definition: A galaxy with a ring-like appearance around the central luminous center. The ring consists of massive, relatively young bright stars. It is believed that ring galaxies result from the head-on collision of two different galaxies.
modified: 2020-11-03T21:33:23.366Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:33:39.198Z
modified: 2020-11-03T21:33:39.231Z

Ring nebulae
type: Concept
alternative label: Ring nebula
broader: Nebulae

Ring singularities
type: Concept
broader: Gravitational singularities
related: Kerr black holes

Ritchey-Chrétien telescopes
type: Concept
broader: Cassegrain telescopes
contributor: AAS Frey.Katie Admin
alternative label: Ritchey-Chretien telescopes
definition: A type of Cassegrain telescope in which the primary mirror is a hyperboloid. It is designed to eliminate coma and spherical aberration, thus providing a relatively large field of view as compared to a more conventional configuration.
modified: 2020-11-03T21:34:54.002Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:35:05.638Z
modified: 2020-11-03T21:35:05.664Z

Roche limit
type: Concept
alternative label: Roche radius
broader: Three-body problem
broader: Tidal interaction
contributor: AAS Frey.Katie Admin
definition: The smallest distance at which a satellite under the influence of its own gravitation and that of a central mass about which it is describing a Keplerian orbit can be in equilibrium. This does not, however, apply to a body held together by the stronger forces between atoms and molecules. At a lesser distance the tidal forces of the primary body would break up the secondary body. The Roche limit is given by the formula d = 1.26 R_M (ρ_M/ρ_m)^(1/3), where R_M is the radius of the primary body, ρ_M is the density of the primary, and ρ_m is the density of the secondary body. This formula can also be expressed as: d = 1.26 R_m (M_M/M_m)^(1/3), where R_m is the radius of the secondary. As an example, for the Earth-Moon system, where R_M = 6,378 km, ρ_M = 5.5 g cm^(-3), and ρ_m = 2.5 g cm^(-3) is 1.68 Earth radii.
modified: 2020-11-24T16:49:39.258Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:29:30.515Z
modified: 2020-11-17T20:29:30.539Z

Roche lobe
type: Concept
broader: Three-body problem
related: Roche lobe overflow
definition: The region around a star in a binary system within which orbiting material is gravitationally bound to that star. The point at which the Roche lobes of the two stars touch is called the inner Lagrangian point.
modified: 2020-11-24T17:01:22.267Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:01:38.294Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-24T17:01:38.264Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Rotating black holes
type: Concept
broader: Classical black holes
narrower: Kerr-Newman black holes
narrower: Kerr black holes
definition: A black hole that possesses angular momentum, as first postulated by Roy C. Kerr in 1963. Opposite of a stationary black hole.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:38:22.554Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:38:35.157Z
modified: 2020-11-03T21:38:35.188Z

Rotation powered pulsars
type: Concept
alternative label: Rotation-powered pulsars
broader: Pulsars

Rovers
type: Concept
broader: Space probes

Bautz-Morgan type
type: Concept
alternative label: Bautz-Morgan class
broader: Galaxy clusters

RR Lyrae variable stars
type: Concept
alternative label: Cluster type variable stars
alternative label: RR Lyrae
alternative label: RR Lyrae type variable stars
alternative label: RR Lyrae variables
narrower: RRab variable stars
narrower: RRc variable stars
alternative label: Bailey type stars
narrower: RRd variable stars
broader: Pulsating variable stars
definition: A member of a large class of pulsating stars of type A2-F6 with periods less than 1 day. They are similar to Cepheids, except that their periods are much shorter and are less luminous. RR Lyrae stars belong to Population II and are often found in globular clusters (hence one of their older names cluster variables) or elsewhere in the galactic halo. They are used as distance indicators (standard candle) out to more than 200 kpc.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:54:22.807Z
modified: 2020-11-03T21:40:24.635Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T21:40:24.602Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

RRab variable stars
type: Concept
broader: RR Lyrae variable stars
alternative label: RRab stars
alternative label: RRa stars
alternative label: RRab
alternative label: RRb stars
alternative label: Bailey type ab stars
narrower: Blazhko effect
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:50:44.618Z

RRc variable stars
type: Concept
broader: RR Lyrae variable stars
alternative label: RRc stars
alternative label: Bailey type c stars
contributor: AAS Frey.Katie
narrower: Blazhko effect
modified: 2019-12-02T16:32:03.470Z

Runaway stars
type: Concept
broader: High-velocity stars
definition: A massive, young, and hot star that is moving quickly through space. Runaways are probably propelled through space from a binary star when its companion has exploded as a supernova, or ejected from a stellar cluster by the dynamical interactions in the system.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:40:49.334Z
modified: 2020-11-03T21:41:08.125Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:41:08.098Z

RV Tauri variable stars
type: Concept
alternative label: RV Tau
alternative label: RV Tauri
alternative label: RV Tauri stars
alternative label: RV Tauri variables
broader: Type II Cepheid variable stars
contributor: AAS Frey.Katie
modified: 2019-12-03T18:41:50.714Z

S-process
type: Concept
alternative label: S process
alternative label: Slow-neutron-capture process
broader: Nucleosynthesis
broader: Stellar nucleosynthesis
contributor: AAS Frey.Katie
definition: A nucleosynthesis process by which chemical elements heavier than copper are formed through a slow flux of neutrons absorbed by atomic nuclei (neutron-capture element). The capture of neutrons occurs on time scales that are long enough to enable unstable nuclei to decay via the emission of a beta particle before absorbing another neutron. Prominent s-process elements include barium, zirconium, and yttrium.
modified: 2020-11-17T20:32:43.985Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T20:32:54.068Z
modified: 2020-11-17T20:32:54.097Z

Be stars
type: Concept
broader: B stars
broader: Early-type emission stars
narrower: Herbig Ae/Be stars
narrower: Lambda Eridani stars
alternative label: Be-type stars
broader: Emission line stars
narrower: B(e) stars
definition: A hot star of spectral type B showing Balmer lines in emission. Be stars are fast rotators (spinning at about 200 km/sec) and have strong stellar winds with important mass loss.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:21:36.032Z
modified: 2020-10-26T19:02:14.114Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T19:02:14.084Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie

S Doradus stars
type: Concept
alternative label: P Cygni stars
broader: Emission line stars
contributor: AAS Frey.Katie Admin
broader: Luminous blue variable stars
definition: A type of massive, blue supergiant, variable star, also known as a Hubble-Sandage variable or a Luminous Blue Variable (LBV). S Doradus stars are the most luminous stars in the Galaxy and are easily identified in other nearby galaxies. They are named after the prototype, S Doradus, in the Large Magellanic Cloud.
modified: 2020-11-04T14:30:14.647Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:32:05.296Z
modified: 2020-11-04T14:32:05.332Z

S stars
type: Concept
alternative label: S type stars
alternative label: S-type stars
alternative label: Se stars
alternative label: Type-S stars
broader: Giant stars
broader: Heavy metal stars
broader: Late-type stars
narrower: Zirconium stars
contributor: AAS Frey.Katie Admin
broader: Stellar spectral types
definition: A red giant of spectral type S whose spectrum is dominated by molecular bands arising from zirconium oxide (ZrO). S stars also have strong cyanogen bands and contain spectral lines of lithium and technetium. Almost all S stars are long-period variables.
modified: 2020-11-04T14:31:25.824Z
editorial note: Definition Provenance
  created: 2020-11-04T14:31:42.583Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T14:31:42.615Z

Sagittarius dwarf spheroidal galaxy
type: Concept
broader: Dwarf spheroidal galaxies
modified: 2020-11-04T14:34:54.243Z
contributor: AAS Frey.Katie Admin
alternative label: Sgr dSph
alternative label: Sgr dE
alternative label: Sag DEG
definition: A satellite galaxy of the Milky Way discovered only in 1994 since most of it is obscured by the Galactic disc. At only 50,000 light years distant from our Galaxy's core, it is travelling in a polar orbit around the Galaxy. Our Galaxy is slowly devouring it, as evidenced by a filament which stretches around the Milky Way's core like a gossamer loop. It is only about 10,000 light-years in diameter, in comparison to the Milky Way's diameter of 100,000 light years. It is populated by old yellowish stars has four known globular clusters: M54, Arp 2, Terzan 7, and Terzan 8. It should not be confused with the Sagittarius Dwarf Irregular Galaxy.
alternative label: Sagittarius dwarf elliptical galaxy
modified: 2020-11-04T14:35:14.192Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:35:14.163Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Saros cycle
type: Concept
alternative label: Saros series
broader: Lunar eclipses
definition: The period of 223 synodic month, equaling 6585.32 days or 18 years, 11.33 days, after which the Sun, Earth, and Moon return to approximately the same relative geometry. When two eclipses are separated by a period of one Saros, they occur at the same node with the Moon at nearly the same distance from Earth and at the same time of year. Thus, the Saros is a useful tool for organizing eclipses into families or series. Each series typically lasts 12 or 13 centuries and contains 70 or more eclipses.
modified: 2020-11-04T14:36:19.605Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:36:30.973Z
editorial note: Definition Provenance
  created: 2020-11-04T14:36:30.947Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Natural satellite formation
type: Concept
broader: Planetary science
contributor: AAS Frey.Katie Admin
alternative label: Satellite formation
modified: 2020-12-11T18:51:32.600Z
related: Natural satellites (Solar system)

Saturn
type: Concept
broader: Solar system gas giant planets
related: Saturnian satellites
modified: 2020-11-24T17:10:03.385Z
definition: The sixth planet from the Sun and the second largest with an equatorial diameter of 120,536 km orbiting at an average distance of 1,429,400,000 km (9.54 astronomical units) from Sun. With an eccentricity of 0.05555, its distance from the Sun ranges from 1.35 billion km (9.024 AU) at its perihelion to 1.509 billion km (10.086 AU) at its aphelion. Its average orbital speed being 9.69 km/s, it takes Saturn 29.457 Earth years (or 10,759 Earth days) to complete a single revolution around the Sun. However, Saturn also takes just over 10 and a half hours (10 hours 33 minutes) to rotate once on its axis. This means that a single year on Saturn lasts about 24,491 Saturnian solar days. Saturn has a mass of 5.6836 x 1026 kg (95.159 Earth masses) and a mean density of 0.687 g cm^(-3). Like Jupiter, Saturn is about 75% hydrogen and 25% helium with traces of water, methane, and ammonia, similar to the composition of the primordial Solar Nebula from which the solar system was formed. The temperature on Saturn is ~ -185 °C. Like Jupiter, Saturn has a solid core of iron-nickel and rock (silicon and oxygen compounds). The core has an estimated mass of 9-22 Earth Masses and a diameter of about 25,000 km (about 2 Earth diameter). The core is enveloped by a liquid metallic hydrogen layer and a molecular hydrogen layer. Saturn's interior is hot (12,000 K at the core). The planet radiates more energy into space than it receives from the Sun. Most of the extra energy is generated by the Kelvin-Helmholtz mechanism as in Jupiter. Saturn has 62 known satellites. Saturn's ring. On 1 July 2004 NASA/ESA's Cassini-Huygens became the first to orbit Saturn, beginning a 13 year mission that revealed many secrets and surprises about Saturn and its system of rings and moons.
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
modified: 2020-11-17T20:34:37.058Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-17T20:34:37.026Z

Saturnian satellites
type: Concept
modified: 2022-06-15T15:32:13.951Z
alternative label: Moons of Saturn
alternative label: Ring shepherds
alternative label: Saturnian moons
broader: Natural satellites (Solar system)
related: Saturn
contributor: AAS Frey.Katie Admin
narrower: Titan
example: Enceladus
example: Mimas
example: Tethys
example: Dione
narrower: Enceladus

Scalar-tensor-vector gravity
type: Concept
alternative label: STVG
broader: Non-standard theories of gravity
alternative label: Modified gravity
modified: 2020-12-17T16:27:01.026Z
contributor: AAS Frey.Katie Admin

Scale height
type: Concept
broader: Planetary atmospheres
modified: 2020-11-17T20:35:10.074Z
contributor: AAS Frey.Katie
definition: The height within which some parameter, such as pressure or density, decreases by a factor of e. For example, an atmospheric scale height of 100 km means that the value at 100 km is 1/e the value at the surface.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:35:19.638Z
modified: 2020-11-17T20:35:19.665Z

Scattered disk objects
type: Concept
alternative label: SDOs
broader: Resonant Kuiper belt objects
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:31:18.411Z

Schmidt-Cassegrain telescopes
type: Concept
broader: Catadioptric telescopes
definition: A mixture of the Cassegrain telescope with a very short focal length and of a Schmidt design (due to the presence of the corrective plate), used mainly in amateur astronomy. The main advantage of this telescope is its compact design. However, Schmidt-Cassegrain telescopes produce fainter images with less contrast than other telescope designs with similar aperture sizes. This is due to the comparatively large secondary mirror required to reflect the light back the eyepiece.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:36:49.972Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:37:14.441Z
modified: 2020-11-03T21:37:14.466Z

Schmidt cameras
type: Concept
alternative label: Schmidt telescopes
broader: Catadioptric telescopes

Schwarzschild black holes
type: Concept
broader: Nonrotating black holes
broader: Uncharged black holes
definition: A black hole with zero angular momentum (non-rotating) and zero electric charge derived from Karl Schwarzschild 1916 exact solution to Einstein's vacuum field equations.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:37:46.467Z
modified: 2020-11-04T14:37:58.265Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:37:58.225Z
  creator: AAS Frey.Katie Admin

Schwarzschild metric
type: Concept
alternative label: Schwarzschild solution
alternative label: Schwarzschild vacuum
broader: Spacetime metric
narrower: Schwarzschild radius
contributor: AAS Frey.Katie
definition: In general relativity, the metric that describes the space-time outside a static mass with spherically symmetric distribution.
modified: 2020-11-17T20:37:25.101Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:37:33.587Z
modified: 2020-11-17T20:37:33.623Z

Schwarzschild radius
type: Concept
alternative label: Gravitational radius
broader: Schwarzschild metric
scope note: Limiting radius of black hole
definition: The critical radius at which a massive body becomes a black hole, i.e., at which light is unable to escape to infinity: R_s = 2GM / c^2, where G is the gravitational constant, M is the mass, and c the speed of light. The formula can be approximated to R_s ≅ 3 x (M/M_sun), in km. Therefore, the Schwarzschild radius for Sun is about 3 km and for Earth about 1 cm.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:46:02.598Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:39:45.790Z
contributor: AAS Frey.Katie
modified: 2020-11-17T20:39:45.823Z

Sculptor dwarf elliptical galaxy
type: Concept
broader: Dwarf elliptical galaxies
contributor: AAS Frey.Katie
definition: A dwarf elliptical galaxy that is a satellite of our Milky Way. It lies about 285,000 light-years away in the constellation Sculptor, and has an absolute magnitude of -11.28 and a mass of about 3 million solar masses. The Sculptor Dwarf is a metal-deficient galaxy containing only 4 percent of the oxygen and carbon elements in our own Galaxy.
modified: 2020-11-17T20:40:24.732Z
modified: 2020-11-17T20:40:34.480Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:40:34.454Z

Seasonal phenomena
type: Concept
broader: Atmospheric effects
related: Earth's seasons
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:16:05.244Z

Secondary cosmic rays
type: Concept
broader: Cosmic rays
contributor: AAS Frey.Katie
definition: A burst of secondary charged and neutral particles arising when primary cosmic rays collide with the atmospheric oxygen or nitrogen nuclei in the upper atmosphere. The collision produces mostly pions (π), along with some kaons (K), antiprotons, and antineutrons. Neutral pions very quickly decay, usually into two gamma rays. Charged pions also decay but after a longer time. Therefore, some of the pions may collide with yet another nucleus of the air before decaying, which would be into a muon and a neutrino. The fragments of the incoming nucleus also interact again, also producing new particles.
modified: 2020-11-17T20:42:42.014Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:42:51.754Z
modified: 2020-11-17T20:42:51.785Z

Secular parallax
type: Concept
broader: Parallax
contributor: AAS Frey.Katie
definition: The angle subtended at a star by a baseline that is the distance the Sun moves in a given interval of time with respect to the local standard of rest (4.09 AU per year).
modified: 2020-11-17T20:43:23.516Z
editorial note: Definition Provenance
  created: 2020-11-17T20:43:33.044Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-17T20:43:33.067Z

Selenology
type: Concept
alternative label: Geology of the Moon
alternative label: Lunar geology
alternative label: Selenodesy
broader: Lunar science
narrower: Lunar features
narrower: Lunar geodesy
narrower: Lunar gravitational field
narrower: Lunar interior
narrower: Lunar magnetic fields
narrower: Lunar surface

Semi-barium stars
type: Concept
alternative label: Semibarium stars
broader: Barium stars

Semi-detached binary stars
type: Concept
alternative label: Semidetached binary stars
broader: Interacting binary stars
narrower: Algol variable stars
narrower: Cataclysmic variable stars
narrower: X-ray binary stars
definition: A binary system whose secondary member fills its Roche lobe but whose primary member does not.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:43:17.890Z
editorial note: Definition Provenance
  created: 2020-11-04T14:43:30.130Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T14:43:30.158Z

Semi-regular variable stars
type: Concept
alternative label: Semiregular variable stars
broader: Late-type giant stars
broader: Long period variable stars
narrower: SRa variable stars
narrower: SRb variable stars
narrower: SRc variable stars
narrower: SRd variable stars
narrower: SRS variable stars
contributor: AAS Frey.Katie Admin
definition: A type of giant or supergiant pulsating variable star, with intermediate or late spectra, showing noticeable periodicity in its light changes, accompanied or sometimes interrupted by various irregularities. Periods lie in the range from 20 to more than 2000 days, while the shapes of the light curve may be rather different and variable with each cycle. The amplitudes may be from several hundredths to several magnitudes (usually 1-2 magnitudes in the V filter). Examples are Betelgeuse, Antares, and Rasalgethi. Semiregular variables are classified in several subtypes: SRA, SRB, SRC, and SRD.
example: Betelgeuse
modified: 2022-06-24T15:27:48.646Z
modified: 2020-11-04T14:44:40.656Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:44:40.624Z

Semimajor axis
type: Concept
alternative label: Semi-major axis
broader: Elliptical orbits
definition: Half the length of the major axis of an ellipse; a standard element used to describe an elliptical orbit.
modified: 2020-11-04T14:45:17.814Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:45:37.223Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T14:45:37.248Z

Semiminor axis
type: Concept
alternative label: Semi-minor axis
broader: Elliptical orbits

Seyfert galaxies
type: Concept
broader: Emission line galaxies
broader: High energy astrophysics
definition: A member of an important class of active galaxies which are characterized by the presence of an intensely bright nucleus in the optical wavelengths (10^9-10^12 L_sun) displaying emission spectral lines. The presence of these emission features, which are not seen in the spectra of normal galaxies, indicates a very high degree of ionization. Moreover, the nucleus radiates non-thermal continuum emission extending over the whole electromagnetic spectrum. It is thought that a massive black hole in the nucleus of a galaxy accretes gas (accretion) from its surrounding environment to power Seyfert galaxies. These galaxies are divided into two types according to the width of their spectral lines. Type 1 Seyfert (Sy 1) galaxies have very broad emission lines (10^3 - 10^4 km s^-1), while Type 2 Seyferts (Sy 2) show relatively narrow lines (several hundred km s^-1). These spectral differences may be the result of viewing the nucleus from different angles. A Type 2 Seyfert galaxy may be a mostly edge-on view of matter spiraling in toward the supermassive black hole, whereas a Type 1 Seyfert provides a more pole-on view, allowing us to see the more turbulent region around the black hole.
modified: 2020-11-04T14:47:16.822Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:47:31.816Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T14:47:31.848Z

Shadow bands
type: Concept
broader: Solar eclipses
contributor: AAS Frey.Katie
modified: 2020-11-17T20:46:40.719Z
definition: Faint wavy lines of alternating light and dark that sometimes can be seen on flat, light-colored surfaces just before and just after a total solar eclipse. The phenomenon results from sunlight distortion by irregularities in the Earth's atmosphere.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:46:51.609Z
modified: 2020-11-17T20:46:51.636Z

Shell burning
contributor: AAS Frey.Katie
type: Concept
broader: Circumstellar shells
scope note: Nuclear fusion in shell
definition: The nuclear reactions in a shell around a star's core that continue after the fuel in the core itself has been exhausted. As the fuel is progressively exhausted, the shell moves outward until it enters regions too cool for the reactions to continue. For example, after the exhaustion of hydrogen in the core, helium burning might take place in the core with a shell of hydrogen burning surrounding it. Stars may have more than one region of shell burning during their stellar evolution, each shell with its own nuclear reactions.
modified: 2020-11-17T20:47:25.334Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-17T20:47:35.310Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-17T20:47:35.339Z

Shepherd satellites
type: Concept
alternative label: Shepherd moons
broader: Planetary rings
definition: A natural satellite in orbit near the edge of a planetary ring, whose gravitational force on the ring particles strongly controls the distribution of material within the ring, creating ringlets and density waves within the ring and sharp edges at ring boundaries. Examples include Saturn's Prometheus and Pandora, which shepherd the narrow outer F ring and the Uranus satellites Cordelia and Ophelia and the epsilon ring. The faster-moving inside satellite accelerates the inner ring particles as it passes them, causing them to spiral out to larger orbits. At the same time the slower-moving outer satellite decelerates the outer ring particles as they pass by, causing them to spiral inward. The result is a narrow, well-defined ring.
modified: 2020-11-04T14:49:41.853Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:49:57.407Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:49:57.382Z

Short period comets
type: Concept
alternative label: Periodic comets
broader: Comets
definition: A comet with a period less than 200 years.
contributor: AAS Frey.Katie Admin
alternative label: Short-period comet
modified: 2020-11-04T14:52:35.833Z
modified: 2020-11-04T14:52:21.698Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:52:21.668Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Short period variable stars
type: Concept
broader: Periodic variable stars
narrower: Beta Cephei variable stars
narrower: Delta Scuti variable stars
alternative label: Short-period variable stars
contributor: AAS Frey.Katie Admin
alternative label: Short-period variable
alternative label: Short-period variables
alternative label: Short period variable
alternative label: Short period variables
definition: A variable star that has a relatively short period with respect to stars of similar types.
modified: 2020-11-04T14:53:27.897Z
modified: 2020-11-04T14:53:39.607Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:53:39.575Z

Siderostats
type: Concept
broader: Stellar tracking devices
definition: A mirror arrangement with clock drive that reflects light from a celestial body to a fixed position.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:54:04.840Z
modified: 2020-11-04T14:54:20.261Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T14:54:20.225Z

Sigma8
type: Concept
alternative label: Sigma 8
alternative label: Sigma-8
broader: Cosmological parameters

Silicate grains
type: Concept
broader: Interstellar dust

Silicon burning
type: Concept
broader: Nucleosynthesis
modified: 2020-11-19T15:24:50.394Z
contributor: AAS Frey.Katie
definition: The nucleosynthetic process taking place in the interior of massive stars whereby silicon is transmuted into iron, nickel, and neighboring nuclei collectively called the iron peak elements.
modified: 2020-11-19T15:25:00.556Z
editorial note: Definition Provenance
  created: 2020-11-19T15:25:00.520Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Silicon monoxide masers
type: Concept
alternative label: SiO masers
alternative label: Silicon-monoxide masers
broader: Astrophysical masers

Silicon stars
type: Concept
broader: Ap stars

Single-dish antennas
type: Concept
broader: Radio telescopes

Single x-ray stars
type: Concept
broader: X-ray stars
contributor: AAS Frey.Katie
modified: 2019-12-13T21:25:34.267Z

Sky brightness
type: Concept
broader: Atmospheric effects
narrower: Night sky brightness
narrower: Twilight
contributor: AAS Frey.Katie
definition: Atmospheric (airglow, auroral emission, artificial light) or extraterrestrial (scattered sunlight from Moon, scattered starlight, interplanetary dust) foreground light that interferes with observations.
modified: 2020-11-19T15:25:31.623Z
editorial note: Definition Provenance
  created: 2020-11-19T15:25:40.050Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T15:25:40.077Z

Sky noise
type: Concept
broader: Astrometry

Sky surveys
type: Concept
broader: Surveys
broader: Catalogs
definition: The observation and recording of large extents of the sky with a particular instrument using one or more wavelengths in the same spectral domain.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T14:55:30.148Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:56:10.013Z
modified: 2020-11-04T14:56:10.050Z

Sloan photometry
type: Concept
alternative label: S d ss photometry
broader: Broad band photometry

Slow novae
type: Concept
alternative label: Novoid
broader: Novae
contributor: AAS Frey.Katie Admin
definition: A type of nova whose light curve exhibits a characteristically slow development, having a rise time of several days, maximum of several weeks, and slower decline.
modified: 2020-11-04T14:56:53.169Z
editorial note: Definition Provenance
  created: 2020-11-04T14:57:04.360Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T14:57:04.386Z

Small Magellanic Cloud
type: Concept
alternative label: S m c
broader: Magellanic Clouds
contributor: AAS Frey.Katie Admin
broader: Magellanic irregular galaxies
alternative label: SMC
definition: An irregular galaxy, the smaller of the two Magellanic Clouds that are satellites of our own Galaxy, lying in the southern constellation Tucana about 20 degrees from the south celestial pole. The SMC covers an area roughly 3 by 5 degrees in dimension and has an overall visual magnitude about +2.7. The SMC is about 10,000 light-years in diameter and some 210,000 light-years (61 kpc) away. It has a visible mass of about 1/50-th that of our Galaxy and 1/10-th of that of the Large Magellanic Cloud (LMC). Its heavy element content is about a factor 5 smaller than that of the Galaxy. The SMC is the third-nearest external galaxy after the Sagittarius Dwarf Spheroidal Galaxy and the LMC.
modified: 2020-11-04T14:58:30.360Z
modified: 2020-11-04T14:58:42.048Z
editorial note: Definition Provenance
  created: 2020-11-04T14:58:42.015Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Small Solar System bodies
type: Concept
alternative label: SSSBs
broader: Solar system
narrower: Comets
narrower: Asteroids
alternative label: SSSB
definition: A term introduced by the International Astronomical Union (August 2006) to name the solar system bodies other than planets and dwarf planets. Small solar system bodies include asteroids, comets, and meteoroids.
narrower: Near-Earth objects
narrower: Interstellar objects
narrower: Trans-Neptunian objects
alternative label: Small Solar System body
contributor: AAS Frey.Katie Admin
modified: 2022-01-04T19:17:46.187Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:59:51.880Z
modified: 2020-11-04T14:59:51.906Z

Bessel photometry
type: Concept
alternative label: Bessel UB VRI photometry
broader: Broad band photometry

Solar-planetary interactions
type: Concept
alternative label: Solar planetary interactions
alternative label: Solar planetary relation
alternative label: Solar-planetary relation
alternative label: Solar/planetary interactions
broader: Planetary science
narrower: Solar-terrestrial interactions
related: Star-planet interactions
contributor: AAS Frey.Katie Admin
scope note: Specific to interactions between the Sun and Solar system planets. The similar concept "Star-planet interactions" is about exoplanets and their stars.
related: Space weather
modified: 2020-12-04T15:09:19.406Z

Solar-terrestrial interactions
type: Concept
alternative label: Solar/terrestrial relations
broader: Solar-planetary interactions
contributor: AAS Frey.Katie Admin
scope note: Specific to interactions between the Sun and Earth. The similar concept "Solar-planetary interactions" is about interactions between the Sun and other Solar system planets, or all of them more generally.
alternative label: Sun-Earth interactions
alternative label: Solar terrestrial relation
modified: 2020-12-17T16:27:56.610Z

Solar abundances
type: Concept
broader: Solar physics
related: Stellar abundances
broader: Chemical abundances
modified: 2020-12-16T15:59:34.002Z
contributor: AAS Frey.Katie Admin

Solar activity
type: Concept
broader: Solar physics
narrower: Solar flares
narrower: Solar prominences
narrower: Solar storm
contributor: AAS Frey.Katie
narrower: Solar active regions
narrower: Solar filaments
narrower: Solar magnetic bright points
related: Stellar activity
definition: The general term for all forms of short-lived phenomena on the Sun, including solar flares, sunspots, prominences, etc., indicating that the Sun is an active star.
modified: 2020-11-19T15:29:53.786Z
modified: 2020-11-19T15:30:04.032Z
editorial note: Definition Provenance
  created: 2020-11-19T15:30:03.994Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Solar physics
type: Concept
alternative label: Astrophysics of the sun
narrower: Solar abundances
narrower: Solar activity
narrower: Solar atmosphere
narrower: Solar electromagnetic emission
narrower: Solar evolution
narrower: Solar faculae
narrower: Solar flares
narrower: Solar granulation
narrower: Solar interior
narrower: Solar motion
narrower: Solar oscillations
narrower: Solar particle emission
narrower: Solar radiation
narrower: Solar rotation
narrower: Solar surface
narrower: Solar wind
narrower: Sunspots
narrower: CNO anomaly
narrower: Helioseismology
alternative label: Solar astronomy
related: Solar neutrinos
related: The Sun
scope note: Specifically the study of the Sun.
scope note: The Sun is not primarily thought of as a subclass of star, because it is discussed with different words in a different literature by a different group of scientists. - jegpeek
top concept of: The Unified Astronomy Thesaurus
alternative label: Solar astrophysics
narrower: Solar mass
narrower: Solar radius
narrower: Solar spectral irradiance
narrower: Solar magnetic fields
related: Stellar physics
definition: The branch of astrophysics concerned with the study of the physical properties of the Sun based on the most detailed observations which can be obtained for a star.
modified: 2022-03-29T17:21:25.592Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T15:56:47.337Z
modified: 2020-11-19T15:57:11.898Z

Solar atmosphere
type: Concept
broader: Solar physics
narrower: Solar chromosphere
narrower: Solar corona
narrower: Solar photosphere
related: Stellar atmospheres
narrower: Limb brightening
contributor: AAS Frey.Katie Admin
narrower: Limb darkening
modified: 2020-11-09T22:11:43.264Z

Solar atmospheric motions
type: Concept
broader: Solar motion

Beta Cephei variable stars
type: Concept
alternative label: Beta canis majoris stars
broader: Multi-periodic variable stars
broader: Pulsating variable stars
broader: Short period variable stars
broader: Early-type variable stars
alternative label: Beta Cephei stars
related: Main sequence stars
alternative label: Beta Cepheid variable stars
scope note: These stars are usually hot blue-white stars of spectral class B and should not be confused with Cepheid variables, which are named after Delta Cephei and are luminous supergiant stars. -- Wikipedia, https://en.wikipedia.org/wiki/Beta_Cephei_variable
modified: 2020-11-24T16:59:27.653Z
contributor: AAS Frey.Katie Admin

Solar constant
type: Concept
broader: Astrometry
definition: The amount of solar radiation in all wavelengths received per unit of time per unit of area on a theoretical surface perpendicular to the Sun's rays and at Earth's mean distance from the Sun. Its mean value is 1367.7 W m^-2 or 1.37 x 106 erg sec^-1 cm^-2. In other words, the solar constant is the mean solar irradiance on the outer atmosphere when the Sun and Earth are spaced at 1 astronomical unit.
modified: 2020-11-24T17:18:01.914Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-19T15:33:41.395Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie
modified: 2020-11-19T15:33:41.424Z

Solar corona
type: Concept
broader: Solar atmosphere
narrower: Solar coronal holes
narrower: Solar coronal loops
narrower: Solar coronal streamers
contributor: AAS Frey.Katie
narrower: Active solar corona
narrower: Solar coronal heating
narrower: Solar E corona
narrower: Solar F corona
narrower: Quiet solar corona
narrower: Solar coronal radio emission
narrower: Solar coronal seismology
narrower: Solar coronal waves
narrower: Solar transition region
related: Stellar coronae
narrower: Solar coronal lines
narrower: Solar coronal plumes
narrower: Solar coronal transients
narrower: Solar K corona
definition: The outermost atmosphere of the Sun immediately above the chromosphere, which can be seen during a total solar eclipse. It consists of hot, extremely tenuous gas extending for millions of kilometer from the Sun's surface.
modified: 2020-11-19T15:39:17.521Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T15:39:28.299Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T15:39:28.328Z

Solar coronal holes
type: Concept
broader: Solar corona
related: Stellar coronal holes
alternative label: Solar M coronal region
alternative label: M regions
alternative label: M region
definition: An area in the solar corona which appears dark in X-rays and ultraviolet light. The gas density in these areas are very low, about 100 times less than that of coronal active regions. The magnetic field lines in a coronal hole extend out into interplanetary space rather than returning to the Sun's surface, as they do in other parts of the Sun (open magnetic field line). Ionized hot gas can escape easily along such a path, and this brings about high speed solar wind streams.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:44:53.719Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:04:20.399Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T15:04:20.431Z

Solar coronal loops
type: Concept
broader: Solar corona
related: Stellar coronal loops
definition: An arc-like structure in the Sun's corona that is found around sunspots and in active regions. These structures are associated with the closed magnetic field lines that connect magnetic regions on the solar surface. The loops are sometimes as high as 10,000 km with their two ends situated in photosphere regions of opposite magnetic polarity. This implies that the coronal loops are tubes of magnetic flux filled with hot plasma. They last for days or weeks but most change quite rapidly.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:07:19.723Z
editorial note: Definition Provenance
  created: 2020-11-04T15:07:31.823Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T15:07:31.855Z

Solar coronal streamers
type: Concept
broader: Solar corona
definition: A bright, narrow stream of particles traveling through the Sun's corona, visible in images taken with a coronagraph or during a total solar eclipse. Coronal streamers represent the most outwardly extended structures in the solar corona and result from the interaction between the solar slow wind and the large-scale magnetic field.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:09:04.255Z
editorial note: Definition Provenance
  created: 2020-11-04T15:09:17.444Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T15:09:17.471Z

Solar cycle
type: Concept
alternative label: Solar activity cycles
alternative label: Solar cycle variations
alternative label: Solar magnetic activity cycle
alternative label: Sun cycle
alternative label: Sun cycles
broader: Helioseismology
narrower: Quiet sun
narrower: Sunspot cycle
narrower: Active sun
contributor: AAS Frey.Katie
narrower: Solar dynamo
definition: The periodic variation in frequency or number of solar active events (sunspots, prominences, flares, and other solar activity) occurring with an interval of about 11 years. The solar cycle was discovered in 1843 by Samuel Heinrich Schwabe (1789-1875), a German apothecary and amateur astronomer, who after 17 years of observations noticed a periodic variation in the average number of sunspots seen from year to year on the solar disk. Solar cycle numbering goes back to the 18th century, when the Cycle 1 peak occurred in 1760. Cycle 23 peaked in 2000, and the following Cycle 24 will reach its maximum in 2013.
modified: 2020-11-19T15:46:01.601Z
modified: 2020-11-19T15:46:12.140Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T15:46:12.107Z

Solar radius
type: Concept
broader: Solar physics
related: Stellar radii
definition: A unit of length, representing the radius of the Sun, used to express the size of stars in astrophysics. It is equivalent to: 695,700 km, 0.00465047 astronomical units, 7.35355 x 10^-8 light-years, and 2.32061 light-seconds.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:16:11.600Z
modified: 2020-11-19T15:58:31.035Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T15:58:31.008Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Solar eclipses
type: Concept
broader: Eclipses
narrower: Shadow bands
narrower: Diamond ring effect
narrower: Flash spectra
definition: An eclipse in which the Earth passes through the shadow cast by the Moon. Solar eclipses only happen when the Moon is new and when the Moon lies close to the node of its orbit.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:18:32.538Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T15:18:46.972Z
modified: 2020-11-04T15:18:47.004Z

Solar evolution
type: Concept
alternative label: Evolution of the sun
broader: Solar physics
narrower: Solar nebulae
related: Stellar evolution

Solar extreme ultraviolet emission
type: Concept
alternative label: Solar EUV emission
broader: Solar electromagnetic emission

Solar faculae
type: Concept
alternative label: Solar facula
broader: Solar physics
contributor: AAS Frey.Katie
related: Stellar faculae
definition: A bright area of the photosphere of the Sun visible in white light and best seen near the solar limb, although they occur all across the Sun. Faculae raise several hundred kilometers above the photosphere and are associated with sunspots. They often appear immediately before the formation of a sunspot group and remain visible for several days or weeks after the disappearance of the spots. Faculae are formed when a strong magnetic field heats a region of the photosphere to higher temperatures than the surrounding area.
modified: 2020-11-19T15:49:06.334Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T15:49:16.374Z
modified: 2020-11-19T15:49:16.403Z

Solar granulation
type: Concept
broader: Solar physics
narrower: Mesogranulation
narrower: Supergranulation
related: Solar granules
contributor: AAS Frey.Katie Admin
related: Stellar granulation
definition: The mottled appearance of the solar photosphere, caused by convective cells, resembling granules, which rises from the interior of the Sun. Each granule has a mean size of about 1,000 km and an upward velocity of about 0.5 km/sec. Granules are separated by intergranular walls about 400 K colder. They emerge from the fragments of the preceding granules and their lifetimes are about 20 minutes.
modified: 2020-11-04T15:22:15.205Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T15:22:26.982Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T15:22:27.010Z

Solar instruments
type: Concept
alternative label: Solar instrumentation
broader: Astronomical instrumentation
definition: An instrument especially designed for solar observations.
modified: 2020-11-04T15:25:57.246Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:26:09.093Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:26:09.062Z

Achondrites
type: Concept
broader: Meteorites
contributor: AAS Frey.Katie
definition: A class of stony meteorites that lack chondrules. They are made of rock that has crystallized from a molten state. Achondrites are relatively rare, accounting for about 8% of all meteorite falls.
modified: 2020-11-03T17:56:07.066Z
editorial note: Definition Provenance
  created: 2020-11-03T17:56:19.250Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T17:56:19.280Z

Bianchi cosmology
type: Concept
broader: Cosmology

Solar macrospicules
type: Concept
broader: Solar spicules

Solar magnetic fields
type: Concept
broader: Helioseismology
narrower: Solar magnetic reconnection
narrower: Solar magnetic flux emergence
narrower: Solar magnetic bright points
narrower: Solar dynamo
broader: Solar physics
related: Stellar magnetic fields
definition: The Sun's magnetic field which is probably created by the differential rotation of the Sun together with the movement of charged particles in the convective zone. Understanding how the solar magnetic field comes about is the fundamental problem of Solar Physics. The solar magnetic field is responsible for all solar magnetic phenomena, such as sunspots, solar flares, coronal mass ejections, and the solar wind. The solar magnetic fields are observed from the Zeeman broadening of spectral lines, polarization effects on radio emission, and from the channeling of charged particles into visible coronal streamers. The strength of Sun's average magnetic field is 1 gauss (twice the average field on the surface of Earth, around 0.5 gauss), and can be as strong as 4,000 Gauss in the neighborhood of a large sunspot.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:01:19.964Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:27:13.362Z
modified: 2020-11-04T15:27:13.388Z

Solar magnetic reconnection
type: Concept
broader: Solar magnetic fields

Solar mass
type: Concept
contributor: AAS Frey.Katie
broader: Solar physics
related: Stellar masses
definition: The amount of mass in our Sun, about 330,000 times the Earth's mass. The solar mass is also the unit in which the masses of other stars, galaxies, and other large celestial bodies are expressed.
modified: 2020-11-19T15:52:29.364Z
modified: 2020-11-19T15:52:40.452Z
editorial note: Definition Provenance
  created: 2020-11-19T15:52:40.425Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Solar motion
type: Concept
broader: Solar physics
narrower: Solar atmospheric motions
narrower: Antapex
narrower: Apex
related: Stellar motion
scope note: With respect to nearby stars

Solar nebulae
type: Concept
alternative label: Solar nebula
broader: Solar evolution
related: Solar system formation
definition: The cloud of interstellar gas and dust from which the Sun and the rest of the solar system initially formed.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:27:38.330Z
modified: 2020-11-04T15:27:51.201Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:27:51.176Z

Solar neighborhood
type: Concept
preferred label: Solar neighbourhood
broader: Milky Way Galaxy physics
broader: Solar system
definition: That part of the Milky Way galaxy lying near the Sun. In fact there is no definition of the exact radius of this region. It is referred to the immediate solar neighborhood (within about 5 pc), the solar neighborhood (within about 25 pc), and the extended solar neighborhood (within a few hundred pc).
modified: 2021-08-24T15:22:43.877Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-19T15:53:36.874Z
editorial note: Definition Provenance
  created: 2020-11-19T15:53:36.834Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Big Bang nucleosynthesis
type: Concept
alternative label: Nucleogenesis
broader: Nucleosynthesis
broader: Big Bang theory

Solar neutrino problem
type: Concept
broader: Neutrino astronomy
contributor: AAS Frey.Katie
definition: A major discrepancy between the flux of neutrinos detected at Earth from the solar core and that predicted by current models of solar nuclear fusion and our understanding of neutrinos themselves. The problem, lasting from the mid-1960s to about 2002, was a considerably lesser detected number of neutrons compared with theoretical predictions. The discrepancy has since been resolved by new understanding of neutrino physics, requiring a modification of the standard model of particle physics, in particular neutrino oscillation.
modified: 2020-11-19T15:54:03.847Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T15:54:13.627Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T15:54:13.656Z

Solar neutrinos
type: Concept
broader: Nuclear astrophysics
broader: Particle astrophysics
related: Solar physics
related: Solar particle emission
definition: A neutrino generated in the Sun. The main source of solar neutrinos is the proton-proton chain of reactions, in which an energy of +28 MeV is shared between the reaction products. These are called low-energy neutrinos. There are less important reactions in the Sun yielding a smaller flux of higher energy neutrinos. The solar neutrino flux can be estimated from the solar luminosity.
modified: 2020-11-04T15:30:10.327Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:30:23.071Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T15:30:23.044Z
  creator: AAS Frey.Katie Admin

Solar neutrons
type: Concept
broader: Solar particle emission

Solar observatories
type: Concept
broader: Observatories

Solar optical telescopes
type: Concept
broader: Optical telescopes
broader: Solar telescopes

Solar parallax
type: Concept
broader: Stellar parallax
contributor: AAS Frey.Katie
definition: The angle subtended (8''.79) by the equatorial radius of the Earth at a distance of 1 astronomical unit.
modified: 2020-11-19T15:55:05.145Z
modified: 2020-11-19T15:55:15.262Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T15:55:15.219Z

Solar photosphere
type: Concept
broader: Solar atmosphere
narrower: Solar granules
related: Stellar photospheres
definition: The visible surface of the Sun (temperature 5700 K), just below the chromosphere and just above the convective zone. The solar photosphere is a thin layer of roughly 300 km wide. Its temperature decreases uniformly with height, from about 6,600 K (pressure 0.868 millibars) at its bottom, to about 4,400 K (pressure 125 mb), where it merges with the chromosphere. The photosphere has a 'rice-grain' appearance, called granulation, caused by rising (hot) and falling (cool) material in the convective cells just below the photosphere. Other main features of the photosphere are sunspots, faculae, and supergranulation.
modified: 2020-11-19T15:56:04.049Z
contributor: AAS Frey.Katie
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:32:20.003Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T15:32:19.974Z

Solar prominences
type: Concept
alternative label: Prominence
alternative label: Solar eruptions
alternative label: Solar prominence
alternative label: Solar prominence eruptions
broader: Solar activity
narrower: Quiescent solar prominence
related: Solar filaments
scope note: A solar filament, but seen above the limb.

Big Bang theory
type: Concept
broader: Origin of the universe
broader: Cosmology
narrower: Photon decoupling
narrower: Recombination (cosmology)
narrower: Reionization
narrower: Big Bang nucleosynthesis
narrower: Cosmological perturbation theory
narrower: Hadron barrier
contributor: AAS Frey.Katie
definition: A theory which states that the Universe came into existence in an 'instantaneous' event some 14 billion years ago. Matter was created in that initial event and as time has gone by the Universe has expanded and the contents evolved into the galaxies and stars and of today. The Big Bang is sometimes described as an 'explosion.' However, matter and energy did not erupt into a pre-existing space, since they came into being simultaneously with space and time.
modified: 2020-11-03T18:47:46.044Z
modified: 2020-11-03T18:48:00.176Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:48:00.150Z

Solar radiation
type: Concept
broader: Solar physics
modified: 2020-11-19T15:57:43.274Z
contributor: AAS Frey.Katie
definition: All the constituents making up the Sun's emission: photons, electrons, protons, neutrinos, and atomic nuclei.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T15:57:53.525Z
modified: 2020-11-19T15:57:53.552Z

Solar radio emission
type: Concept
broader: Solar electromagnetic emission

Solar radio telescopes
type: Concept
broader: Radio telescopes
broader: Solar telescopes

Solar rotation
type: Concept
broader: Solar physics
related: Stellar rotation
contributor: AAS Frey.Katie
narrower: Solar differential rotation
definition: The motion of the Sun around an axis which is roughly perpendicular to the plane of the ecliptic; the Sun's rotational axis is tilted by 7.25° from perpendicular to the ecliptic. It rotates in the counterclockwise direction (when viewed from the north), the same direction that the planets rotate (and orbit around the Sun). The Sun's rotation is differential, i.e. the period varies with latitude on the Sun (differential rotation). Equatorial regions rotate in about 25.6 days. The regions at 60 degrees latitude rotate more slowly, in about 30.9 days.
modified: 2020-11-19T15:59:02.762Z
modified: 2020-11-19T15:59:13.623Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T15:59:13.594Z
  creator: AAS Frey.Katie

Solar system
type: Concept
broader: Solar system astronomy
narrower: Meteoroids
narrower: Natural satellites (Solar system)
narrower: Oort cloud
narrower: Planetary rings
narrower: Solar system planets
narrower: Small Solar System bodies
narrower: Solar neighborhood
narrower: The Moon
narrower: The Sun
narrower: Asteroid belt
narrower: Heliosphere
narrower: Interplanetary medium
narrower: Kuiper belt
related: Cosmogony
narrower: Space weather
definition: The collective name for the Sun and all objects gravitationally bound to it. These objects are the eight planets, their 166 known moons, five dwarf planets, and billions of small bodies. The small bodies include asteroids, icy Kuiper belt objects, comets, meteoroids, and interplanetary dust. The solar system is roughly a sphere with a radius greater than 100,000 AU. Planets, satellites, and all interplanetary material together comprise only about 1/750 of the total mass. Geochemical dating methods show that the solar system chemically isolated itself from the rest of the Galaxy (4.7 ± 0.1) x 10^9 years ago.
contributor: AAS Frey.Katie Admin
narrower: Dwarf planets
related: Exoplanet systems
related: Solar system evolution
related: Solar system formation
modified: 2022-06-15T19:32:22.690Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:00:07.120Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:00:07.155Z
contributor: AAS Frey.Katie

Solar system astronomy
type: Concept
alternative label: Planetary astronomy
narrower: Planetary science
narrower: Solar system
narrower: Earth-moon system
narrower: Lunar science
scope note: Referring specifically the study of our solar system, not exoplanets.
top concept of: The Unified Astronomy Thesaurus
contributor: AAS Frey.Katie Admin
modified: 2022-06-15T19:32:22.691Z

Binary pulsars
type: Concept
broader: Pulsars
broader: Compact binary stars

Solar system formation
type: Concept
broader: Planetary system formation
related: Solar nebulae
related: Solar system
modified: 2022-06-15T19:31:53.758Z
contributor: AAS Frey.Katie Admin

Solar telescopes
type: Concept
alternative label: Tower telescope
broader: Telescopes
narrower: Radioheliographs
narrower: Solar optical telescopes
narrower: Solar radio telescopes
definition: A telescope designed so that heating effects produced by the Sun do not distort the images.
modified: 2020-11-04T16:07:49.693Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T16:08:01.279Z
modified: 2020-11-04T16:08:01.311Z

Solar ultraviolet emission
type: Concept
alternative label: Solar UV emission
broader: Solar electromagnetic emission

Solar wind
type: Concept
broader: Solar physics
narrower: Heliopause
related: Stellar winds
related: Interplanetary physics
narrower: Fast solar wind
narrower: Slow solar wind
contributor: AAS Frey.Katie
definition: A mass outflow, consisting of protons, electrons, and other subatomic particles, expelled constantly from the solar corona at about 500 km per second. The solar mass-loss rate in this phenomenon amounts to about 2 x 10^-14 solar masses per year, or about 106 tons per second.
modified: 2020-11-19T16:00:57.493Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:01:14.924Z
modified: 2020-11-19T16:01:14.964Z

Solar wind termination
type: Concept
broader: Interplanetary physics

Solar x-ray emission
type: Concept
broader: Solar electromagnetic emission
modified: 2019-12-13T21:25:49.326Z
contributor: AAS Frey.Katie

Solstice
type: Concept
broader: Equatorial coordinate system
narrower: Summer solstice
narrower: Winter solstice
contributor: AAS Frey.Katie
definition: Either of the two points on the ecliptic at which the apparent longitude of the Sun is 90° or 270°. Also the time at which the Sun is at either point. Solstices occur when the Earth's axis is oriented directly toward or away from the Sun, causing the Sun to reach its northernmost and southernmost extremes.
modified: 2020-11-19T16:01:46.581Z
modified: 2020-11-19T16:01:56.751Z
editorial note: Definition Provenance
  created: 2020-11-19T16:01:56.725Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

South celestial pole
type: Concept
alternative label: S c p
alternative label: S. c. p.
broader: Celestial poles
contributor: AAS Frey.Katie
definition: The point in the southern hemisphere where the rotation axis of the Earth touches the celestial sphere. In contrast to the north celestial pole, no bright star is visible in that direction.
modified: 2020-11-19T16:02:33.861Z
modified: 2020-11-19T16:02:45.564Z
editorial note: Definition Provenance
  created: 2020-11-19T16:02:45.537Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

South ecliptic pole
type: Concept
alternative label: S e p
alternative label: S. e. p.
broader: Ecliptic poles

Binary stars
type: Concept
alternative label: Binaries
broader: Multiple stars
narrower: Relativistic binary stars
narrower: Spectroscopic binary stars
narrower: Visual binary stars
narrower: Wide binary stars
narrower: Close binary stars
narrower: Companion stars
narrower: Detached binary stars
narrower: Eclipsing binary stars
narrower: Astrometric binary stars
narrower: Interferometric binary stars
related: Optical bursts
related: Optical double stars
narrower: Double periodic variable stars
definition: Two stars gravitationally bound to each other, so that they revolve around their common center of gravity.
contributor: AAS Frey.Katie Admin
modified: 2022-06-24T15:33:45.834Z
example: Sirius
editorial note: Definition Provenance
  created: 2020-10-26T19:10:18.808Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie
modified: 2020-10-26T19:10:18.837Z

South galactic pole
type: Concept
alternative label: S g p
alternative label: S. g. p.
broader: Galactic poles

Space astrometry
type: Concept
broader: Astrometry

Space debris
type: Concept
alternative label: Debris
broader: Space vehicles
contributor: AAS Frey.Katie
definition: Man-made objects in orbit around the Earth that no longer serve any useful purpose. The estimated number of debris include about 22,000 tractable objects larger than 10 cm in all orbits, of which 2,200 are dead satellites and last stages of the rocket that put them in orbit. There are also left-overs from spacecraft and mission operations, such as bolts, lens caps, clamp bands, auxiliary motors, etc. The debris presents a threat because of their high speeds, which ranges between 15 and 20 km/sec. Also called space junk, space waste, orbital debris.
modified: 2020-11-19T16:03:14.375Z
editorial note: Definition Provenance
  created: 2020-11-19T16:03:23.941Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:03:23.977Z

Space observatories
type: Concept
alternative label: Orbiting observatory
broader: Observatories
narrower: Gamma-ray observatories
narrower: Hubble Space Telescope
narrower: Infrared Astronomical Satellite
narrower: James Webb Space Telescope
contributor: AAS Frey.Katie Admin
modified: 2022-06-15T19:26:54.789Z
narrower: Gaia

Space plasmas
type: Concept
alternative label: Astrophysical plasmas
broader: Plasma astrophysics
narrower: Alfven waves

Space probes
type: Concept
alternative label: Probe
broader: Space vehicles
narrower: Orbiters
narrower: Planetary probes
narrower: Rovers
narrower: Deep space probes
narrower: Flyby missions
narrower: Landers
narrower: Lunar probes
definition: A spacecraft carrying instruments intended for use in exploration of the physical properties of outer space or celestial bodies other than Earth.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T16:17:05.398Z
modified: 2020-11-04T16:17:19.239Z
editorial note: Definition Provenance
  created: 2020-11-04T16:17:19.205Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Space research
type: Concept
alternative label: Space science
broader: Astronomical research
narrower: Microgravity

Space telescopes
type: Concept
alternative label: Space based telescopes
alternative label: Space-based telescopes
broader: Space vehicle instruments
broader: Telescopes
narrower: Ultraviolet telescopes
narrower: X-ray telescopes
narrower: Gamma-ray telescopes
narrower: Infrared telescopes
definition: A telescope which is placed in an orbit around the Earth and operates through commands from sent from the control center on Earth, such as Hubble space telescope, Herschel satellite, Infrared Astronomical Satellite (IRAS), Infrared Space Observatory (ISO), International Ultraviolet Explorer (IUE), Planck Satellite, Spitzer Space Telescope.
contributor: AAS Frey.Katie Admin
modified: 2020-12-03T20:51:19.234Z
editorial note: Definition Provenance
  created: 2020-11-04T16:22:30.208Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T16:22:30.238Z

Space vehicle instruments
type: Concept
alternative label: Space vehicle instrumentation
broader: Space vehicles
narrower: Space telescopes

Space vehicles
type: Concept
broader: Astronomical instrumentation
narrower: Space debris
narrower: Space probes
narrower: Space vehicle instruments
narrower: Artificial satellites
narrower: Hall thrusters
narrower: Space stations
narrower: Rockets

Bipolar nebulae
type: Concept
alternative label: Bipolar nebula
broader: Nebulae
definition: An interstellar cloud of ionized gas with two main lobes which lie symmetrically on either side of a central star. The bipolar shape is generally due to the ejection of material by the central star in opposing directions.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:27:59.361Z
modified: 2020-11-02T16:28:10.154Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:28:10.118Z

Spacetime metric
type: Concept
broader: General relativity
narrower: Schwarzschild metric
narrower: Friedmann-Robertson-Walker metric
narrower: Kerr metric

Special relativity
type: Concept
alternative label: Special theory of relativity
broader: Relativity
narrower: Relativistic aberration
definition: The theory formulated by A. Einstein in 1905, which is based on the following two postulates: 1) Principle of relativity: The laws of physical phenomena are the same when studied in terms of two reference systems moving at a constant velocity relative to each other. 2) Principle of constancy: The velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer. The term 'special theory of relativity' refers to the restriction in the first postulate to reference systems moving at a constant velocity relative to each other (inertial reference frame).
modified: 2020-11-24T19:32:12.018Z
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-19T16:05:39.656Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:05:39.686Z

Speckle interferometry
type: Concept
broader: Interferometry
contributor: AAS Frey.Katie
definition: A technique for generating a clear composite image of a celestial object blurred by atmospheric turbulence in which a large number of short-exposure photographs are mathematically correlated by a computer. By comparing the behavior of the speckles in a series of images it is possible to approach the theoretical resolution of the telescope.
modified: 2020-11-19T16:06:09.542Z
modified: 2020-11-19T16:06:20.049Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:06:20.012Z

Spectral index
type: Concept
broader: Radio astronomy
broader: Astrometry

Spectrometers
type: Concept
broader: Astronomical instrumentation
narrower: Mass spectrometers
contributor: AAS Frey.Katie Admin
definition: A spectrograph in which the spectrum is recorded by electronic means so that wavelength, intensity, etc. can be measured. An instrument for determining the distribution of energies in a beam of particles.
modified: 2020-11-24T17:22:21.016Z
editorial note: Definition Provenance
  created: 2020-11-04T16:27:43.722Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T16:27:43.754Z

Spectrophotometric standards
type: Concept
broader: Spectrophotometry

Spectrophotometry
type: Concept
broader: Photometry
narrower: Spectrophotometric standards
narrower: Flux calibration
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T20:13:06.661Z
definition: Measurement of the absolute fluxes of the components of different frequencies in the spectrum of a light source.
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-19T16:07:37.812Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:07:37.848Z

Spectroscopic binary stars
type: Concept
alternative label: Spectroscopic binaries
alternative label: Spectrum binary stars
broader: Binary stars
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:53:25.245Z

Spectroscopy
type: Concept
alternative label: Astronomical spectroscopy
broader: Astronomical techniques
narrower: Lyman alpha forest
narrower: Atomic spectroscopy
narrower: Molecular spectroscopy
narrower: Transmission spectroscopy
contributor: AAS Frey.Katie Admin
narrower: Radio spectroscopy
narrower: Galaxy spectroscopy
definition: The study of spectral lines from different atoms and molecules. Spectroscopy is an important part of studying the physical and chemical properties of astronomical objects.
broader: Experimental techniques
modified: 2022-06-11T21:53:30.845Z
narrower: Electronic spectroscopy
narrower: Rotational spectroscopy
narrower: Vibrational spectroscopy
narrower: Ice spectroscopy
narrower: Infrared spectroscopy
narrower: Gamma-ray spectroscopy
narrower: Ultraviolet spectroscopy
contributor: AAS Frey.Katie
modified: 2020-11-19T16:08:51.509Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:08:51.481Z

Spiral arms
type: Concept
related: De Vaucouleurs Sandage classification
broader: Galaxy structure
definition: The region in a spiral galaxy that contains concentrations of gas, dust, and massive stars. Spiral arms are created by density waves.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T16:30:33.486Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T16:30:57.942Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T16:30:57.978Z

Bipolar sunspot groups
type: Concept
broader: Sunspot groups

Spiral galaxies
type: Concept
alternative label: S galaxies
broader: Disk galaxies
narrower: Milky Way Galaxy
narrower: Barred spiral galaxies
narrower: Triangulum Galaxy
narrower: Unbarred spiral galaxies
narrower: Andromeda Galaxy
related: De Vaucouleurs Sandage classification
related: Hubble classification scheme
modified: 2020-11-04T16:31:30.767Z
definition: A galaxy with a prominent nuclear bulge and luminous spiral arms of gas, dust, and young stars that wind out from the nucleus. Masses span the range from 10^10 to 10^12 solar masses.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T16:31:42.813Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T16:31:42.784Z

Spiral pitch angle
type: Concept
alternative label: Galactic pitch angle
broader: Galaxy structure

Spokes
type: Concept
broader: Planetary rings
definition: In Saturn's rings, changing structures in the radial direction. It is thought that gravitational forces alone cannot account for the spoke structure, and it has been proposed that electrostatic repulsion between ring particles may play a role.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T16:32:30.120Z
modified: 2020-11-04T16:32:41.770Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T16:32:41.738Z
  creator: AAS Frey.Katie Admin

Standard candles
type: Concept
broader: Stellar distance

Standard stars
type: Concept
broader: Astrometry
narrower: Photometric standard stars
narrower: Comparison stars
contributor: AAS Frey.Katie
definition: Stars for which accurate color indices and/or magnitudes exist, defining a standard system.
modified: 2020-11-19T16:10:15.107Z
modified: 2020-11-19T16:10:28.575Z
editorial note: Definition Provenance
  created: 2020-11-19T16:10:28.544Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Star atlases
type: Concept
broader: Astronomical reference materials

Star clusters
type: Concept
alternative label: Cluster of stars
alternative label: Star clouds
broader: Stellar astronomy
narrower: Stellar associations
narrower: Globular star clusters
related: Field stars
narrower: Protoclusters
narrower: Moving clusters
narrower: Open star clusters
narrower: Young massive clusters
contributor: AAS Frey.Katie Admin
definition: A group of stars held together by the mutual gravitational attraction of its members, which are physically related through common origin. They are of two types: open clusters and globular clusters.
modified: 2020-11-04T16:34:10.715Z
modified: 2020-11-04T16:34:23.699Z
editorial note: Definition Provenance
  created: 2020-11-04T16:34:23.673Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Star counts
type: Concept
alternative label: Star distribution
alternative label: Stellar statistics
broader: Surveys
broader: Astronomical models
definition: The number of stars that appear in a given region of sky, usually counted on a photographic plate or CCD image.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T16:41:27.255Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T16:41:44.373Z
modified: 2020-11-04T16:41:44.402Z

Star formation
type: Concept
broader: Stellar physics
narrower: Star forming regions
contributor: AAS Frey.Katie
definition: The process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy, star formation includes the study of the interstellar medium and molecular clouds as precursors to the star formation process as well as the study of young stellar objects.
modified: 2020-11-19T16:12:03.291Z
modified: 2020-11-19T16:12:15.519Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:12:15.478Z
  creator: AAS Frey.Katie

BL Herculis variable stars
type: Concept
contributor: AAS Frey.Katie
broader: Type II Cepheid variable stars
alternative label: BL Herculis stars
modified: 2019-12-03T18:41:48.453Z

Starburst galaxies
type: Concept
broader: Active galaxies
broader: Galaxies
narrower: Infrared galaxies
definition: A galaxy showing a short-lived intense period of star formation that is unsustainable over the Hubble time due to the limited supply of gas within a galaxy. Starburst galaxies were first classified by Searle & Sargent (1972) and Searle et al. (1973), based on the blue colors produced by the massive stars formed during the burst. In the local Universe, starbursts create approximately 10% of the radiant energy and 20% of the massive stars. At z = 1, starburst characteristics are found in 15% of galaxies, presumably attributable to the greater amounts of gas typically present in young galaxies and increased galactic interactions. The starburst's impact on a galaxy and the surrounding intergalactic medium is primarily due to the consumption of gas that fuels the burst and the feedback from massive stars formed in the burst.
contributor: AAS Frey.Katie Admin
alternative label: Starburst galaxy
related: Post-starburst galaxies
modified: 2020-11-12T21:29:51.934Z
modified: 2020-11-04T16:45:58.544Z
editorial note: Definition Provenance
  created: 2020-11-04T16:45:58.515Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Starlight polarization
type: Concept
alternative label: Star light polarization
preferred label: Starlight polarisation
broader: Stellar properties
contributor: AAS Frey.Katie Admin
modified: 2021-09-27T15:44:25.141Z

Starspots
type: Concept
alternative label: Star spots
broader: Stellar physics
related: Sunspots
definition: A phenomenon similar to a sunspot but occurring on the surface of a star other than Sun. Due to spatial resolution constraints, starspots so far observed are in general much larger than those on the Sun, up to about 30% of the stellar surface may be covered, corresponding to sizes 100 times greater than those on the Sun.
modified: 2020-11-04T16:46:55.040Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T16:47:07.049Z
modified: 2020-11-04T16:47:07.078Z

Statistical parallax
type: Concept
broader: Parallax
contributor: AAS Frey.Katie
definition: The mean parallax of a group of stars that are all at approximately the same distance, as determined from their radial velocities and proper motions.
modified: 2020-11-19T16:13:41.766Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:13:54.864Z
modified: 2020-11-19T16:13:54.906Z

Steady-state theory
type: Concept
alternative label: Steady state theory
broader: Origin of the universe

Stellar-interstellar interactions
type: Concept
broader: Interstellar medium
narrower: Astrospheres
narrower: Stellar jets
narrower: Stellar winds
narrower: Interstellar medium wind

Stellar abundances
type: Concept
broader: Chemical abundances
related: Solar abundances
contributor: AAS Frey.Katie Admin
broader: Stellar physics
modified: 2020-12-16T16:30:26.798Z

Stellar accretion
type: Concept
broader: Accretion
broader: Stellar properties
related: Stellar accretion disks

Stellar accretion disks
type: Concept
alternative label: Stellar accretion discs
broader: Late stellar evolution
related: Stellar accretion

BL Lacertae objects
type: Concept
alternative label: BL Lac objects
broader: Active galaxies

Stellar ages
type: Concept
broader: Stellar properties

Stellar associations
type: Concept
alternative label: Star associations
broader: Star clusters
narrower: O associations
narrower: OB associations
narrower: R associations
narrower: T associations
related: Stellar kinematics
definition: A large, loose grouping of 10 to 1000 stars that are of similar spectral type and share a common origin. The members move together through space, but have become gravitationally unbound. Stellar associations are primarily identified by their common movement vectors and ages.
modified: 2020-11-05T20:28:32.807Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T20:28:46.006Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T20:28:45.973Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Stellar astronomy
type: Concept
alternative label: Stellar astrophysics
narrower: Star clusters
narrower: Stellar physics
narrower: Stellar populations
narrower: Stellar remnants
narrower: Stellar types
narrower: Circumstellar matter
narrower: Asteroseismology
top concept of: The Unified Astronomy Thesaurus
contributor: AAS Frey.Katie
definition: The branch of astronomy that deals with the study of stars, their physical properties, formation, and evolution.
modified: 2020-11-19T16:14:40.435Z
narrower: Galactic archaeology
modified: 2020-11-19T16:14:51.551Z
editorial note: Definition Provenance
  created: 2020-11-19T16:14:51.522Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Stellar atmospheres
type: Concept
broader: Stellar physics
narrower: Stellar photospheres
narrower: Stellar chromospheres
narrower: Stellar coronae
related: Astrophysical masers
related: Solar atmosphere
related: Stellar atmospheric opacity

Stellar atmospheric opacity
type: Concept
alternative label: Stellar atmospheric opacities
alternative label: Stellar opacities
alternative label: Stellar opacity
broader: Astronomical optics
related: Stellar atmospheres

Stellar bridges
type: Concept
broader: Interstellar medium
scope note: Between galaxies

Stellar classification
type: Concept
alternative label: Spectra classification
alternative label: Spectral classification
alternative label: Spectral type
alternative label: Spectrum classification
alternative label: Stellar spectral classification
alternative label: Stellar spectrum classification
broader: Classification systems
related: O stars
related: OB stars
related: B stars
related: Wolf-Rayet stars
related: A stars
related: F stars
related: G stars
related: K stars
related: M stars
narrower: Henry Draper catalog
narrower: Morgan-Keenan classification
definition: The systematic grouping of stars and stellar objects into categories on the basis of physical, morphological, or evolutionary characteristics.
contributor: AAS Frey.Katie Admin
modified: 2020-12-03T20:55:49.686Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T20:04:03.563Z
modified: 2020-10-26T20:04:03.586Z
contributor: AAS Frey.Katie

Black hole physics
type: Concept
broader: High energy astrophysics
narrower: Penrose process
narrower: Photon sphere
narrower: Quasinormal modes
narrower: Bekenstein-Hawking entropy
narrower: Black hole spin-flip
narrower: Black hole thermodynamics
narrower: Trans-Planckian physics
narrower: Ergosphere
narrower: Event horizons
narrower: Hawking radiation
narrower: Kruskal diagram
related: Black holes
narrower: M-sigma relation
contributor: AAS Frey.Katie Admin
modified: 2023-02-03T18:28:24.077Z

Stellar colors
type: Concept
preferred label: Stellar colours
broader: Stellar properties
modified: 2021-08-20T13:56:06.560Z
contributor: AAS Frey.Katie Admin

Stellar diffusion
type: Concept
broader: Stellar processes

Stellar distance
type: Concept
alternative label: Cosmic distance ladder
alternative label: Cosmic distance scale
alternative label: Extragalactic Distance Scale
broader: Astrometry
narrower: Standard candles
narrower: Cepheid distance
narrower: Distance indicators
narrower: Faber-Jackson distance
related: Stellar parallax

Stellar dynamics
type: Concept
broader: Stellar physics
narrower: Supernova dynamics
modified: 2020-12-17T16:39:52.829Z
definition: The field of astrophysics that describes systems of many point mass particles whose mutual gravitational interactions determine their orbits. These systems include star clusters, globular clusters, and galaxies. Stellar dynamics deals with systems in which each member contributes importantly to the overall gravitational field and is usually concerned with the statistical properties of many orbits. It can be compared to the kinetic theory of gases developed in the late 19th century. In contrast, celestial mechanics deals with systems where the gravitational force of a massive planet or star determines the orbits of its satellites.
contributor: AAS Frey.Katie Admin
modified: 2020-11-19T16:15:46.715Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:15:46.680Z
contributor: AAS Frey.Katie

Stellar effective temperatures
type: Concept
broader: Stellar properties

Stellar evolution
type: Concept
alternative label: Evolution of stars
alternative label: Star cycle
alternative label: Stellar cycle
broader: Stellar physics
narrower: Nonstandard evolution
narrower: Carbon flashes
narrower: Early stellar evolution
narrower: Eruptive phenomena
narrower: Initial mass function
narrower: Late stellar evolution
related: Solar evolution
related: Young stellar objects
related: Schonberg-Chandrasekhar limit
related: Stellar evolutionary models
narrower: Helmholtz-Kelvin contraction
narrower: Multiple star evolution
definition: The gradual changes in physical state (spectrum, luminosity, temperature) and chemical composition that occurs during the life of a star.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:11:02.022Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-19T16:16:18.582Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:16:18.611Z

Active galactic nuclei
type: Concept
alternative label: AGN
broader: Active galaxies
broader: Galaxy nuclei
broader: High energy astrophysics
narrower: Quasars
narrower: Radio cores
narrower: Radio hot spots
narrower: Radio jets
narrower: Radio lobes
narrower: Radio plumes
narrower: Relativistic disks
narrower: Blazars
related: Radio sources
related: AGN host galaxies
narrower: Low-luminosity active galactic nuclei
narrower: High-luminosity active galactic nuclei
narrower: X-ray active galactic nuclei
narrower: Radio active galactic nuclei
alternative label: AGNs
contributor: AAS Frey.Katie Admin
definition: A central region of an active galaxy, which is a light-year or less in diameter and has an abnormally high luminosity. The nucleus emits high energy radiation (gamma rays, X-rays, ultraviolet) and shows variability over various time-scales, sometimes very short (hours to weeks). Emission line spectra reveal high velocity motions up to 10^4 km s^-1. AGNs are divided into two main types. Type I refers to an AGN whose nucleus is visible (the spectra has both narrow and broad emission lines), while in type II AGN, the broad line region (BLR) is obscured and the lines are very narrow. This may be due either to the viewing angle or some intrinsic difference in structure.
modified: 2020-11-06T01:47:26.534Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T17:59:19.200Z
contributor: AAS Frey.Katie
modified: 2020-11-03T17:59:19.234Z

Black hole spin-flip
type: Concept
alternative label: Spin-flip
broader: Black hole physics

Stellar feedback
type: Concept
broader: Galaxy formation
contributor: AAS Frey.Katie
definition: The process whereby large quantities of energy and momentum are released into the gas surrounding star formation regions in galaxies. More specifically, massive stars inject energy, mass, and metals back to the interstellar medium through stellar winds and supernova explosions. Feedback inhibits further star formation either by removing gas from the galaxy, or by heating it to temperatures that are too high to form new stars. Observations reveal feedback in the form of galactic-scale outflows of gas in galaxies with high star formation rates, especially in the early Universe. Feedback in faint, low-mass galaxies probably facilitated the escape of ionizing radiation from galaxies when the Universe was about 500 million years old, so that the hydrogen between galaxies changed from neutral to ionized, a process called reionization.
modified: 2020-11-19T16:16:54.298Z
modified: 2020-11-19T16:17:07.674Z
editorial note: Definition Provenance
  created: 2020-11-19T16:17:07.646Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Stellar flares
type: Concept
broader: Stellar phenomena
narrower: Optical flares
narrower: Stellar x-ray flares
narrower: Disk flaring
related: Solar flares

Stellar jets
type: Concept
alternative label: Bipolar outflows
alternative label: Jet outflows
broader: Stellar-interstellar interactions
broader: Jets
related: Stellar mass loss

Stellar kinematics
type: Concept
broader: Galaxy physics
narrower: Stellar motion
related: Stellar associations

Stellar luminosities
type: Concept
alternative label: Salpeter IMF
alternative label: Salpeter function
alternative label: Stellar luminosity
broader: Stellar properties

Black hole thermodynamics
type: Concept
alternative label: Thermodynamics of black holes
broader: Black hole physics

Stellar mass black holes
type: Concept
alternative label: Stellar black holes
broader: Astrophysical black holes

Stellar motion
type: Concept
broader: Stellar kinematics
narrower: Proper motions
related: Solar motion

Stellar nucleosynthesis
type: Concept
broader: Nucleosynthesis
narrower: S-process
narrower: Helium burning
narrower: Hydrogen burning
modified: 2020-11-19T16:17:37.305Z
contributor: AAS Frey.Katie
definition: The nuclear reaction process taking place inside stars, whereby chemical elements are produced from pre-existing nuclei heavier than hydrogen and helium.
modified: 2020-11-19T16:17:47.369Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:17:47.338Z

Stellar parallax
type: Concept
broader: Parallax
narrower: Solar parallax
related: Stellar distance
contributor: AAS Frey.Katie
definition: The apparent difference in the position of a celestial object as seen by an observer from two widely separated locations. The parallax of an object can be used to derive its distance. The relationship between the parallax angle p (measured in seconds of arc) and the distance d (measured in astronomical units) is given by d = 206,264 / p. For a parallax angle p = 1'', the distance to the star would correspond to 206,264 AU. By convention, the distance unit parsec is defined to be equivalent to 206,264 AU. Therefore, the parallax relation takes the much simpler form: d (in pc) = 1/p (in seconds of arc). The first star whose parallax was measured was 61 Cygni (Bessel, 1838).
modified: 2020-11-19T16:19:14.992Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:19:32.462Z
modified: 2020-11-19T16:19:32.487Z

Black holes
type: Concept
broader: Compact objects
broader: High energy astrophysics
narrower: Classical black holes
narrower: Astrophysical black holes
related: Black hole physics
related: Gravitational singularities
contributor: AAS Frey.Katie
definition: A fantastically compact object, predicted by the theory of general relativity, whose gravity is so powerful that not even light can escape from it. A black hole forms when matter collapses to infinite density, producing a singularity of infinite curvature in the fabric of space-time. Each black hole is surrounded by an event horizon, at which the escape velocity is the speed of light. The Schwarzschild radius for the Sun is about 3 km and for the Earth about 1 cm. There is observational evidence for black holes on a remarkable range of scales in the Universe: stellar black hole, intermediate-mass black hole, primordial black hole, mini black hole, supermassive black hole, Schwarzschild black hole, Kerr black hole.
modified: 2020-10-26T19:51:18.206Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:51:35.180Z
modified: 2020-10-26T19:51:35.209Z

Stellar photometry
type: Concept
broader: Photometry
contributor: AAS Frey.Katie
definition: The precise measurement of a star's brightness, usually through several specific wavelength bands.
modified: 2020-11-19T16:19:57.632Z
modified: 2020-11-19T16:20:07.484Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:20:07.452Z

Stellar physics
type: Concept
alternative label: Physics of stars
broader: Stellar astronomy
narrower: Star formation
narrower: Starspots
narrower: Stellar atmospheres
narrower: Stellar dynamics
narrower: Stellar evolution
narrower: Stellar phenomena
narrower: Stellar processes
narrower: Stellar properties
narrower: Stellar structures
narrower: Stellar winds
related: Gravitation
related: Hertzsprung Russell diagram
narrower: Stellar abundances
related: Solar physics
narrower: Stellar granulation
contributor: AAS Frey.Katie
definition: The field of astrophysics concerned with the study of the physical characteristics of stars, more specifically their internal structure, physical processes taking place in their interiors, atmospheres, stellar winds, mass loss, interaction with the interstellar medium, as well as the physical laws governing star formation.
modified: 2020-11-19T16:20:35.782Z
modified: 2020-11-19T16:20:45.400Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:20:45.369Z

Stellar populations
type: Concept
broader: Stellar astronomy
narrower: Population I stars
narrower: Population II stars
narrower: Population III stars
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:14:22.283Z

Stellar processes
type: Concept
broader: Stellar physics
narrower: Stellar diffusion

Stellar pulsations
type: Concept
broader: Stellar phenomena
narrower: Multi-periodic pulsation
narrower: Non-radial pulsations
narrower: Pulsation modes
narrower: Radial pulsations
contributor: AAS Frey.Katie
modified: 2020-07-14T14:34:26.144Z

Stellar rings
type: Concept
broader: Galaxy stellar halos

Stellar rotation
type: Concept
broader: Stellar properties
narrower: Radiative braking
narrower: Gravity darkening
related: Solar rotation
related: von Zeipel theorem
definition: The spinning of a star about its axis, due to its angular momentum. Stars do not necessarily rotate as solid bodies, and their angular momentum may be distributed non-uniformly, depending on radius or latitude. Thus the equator of the star can rotate at a different angular velocity than the higher latitudes. These differences in the rate of rotation within a star may have a significant role in the generation of a stellar magnetic field.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:24:35.632Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:21:21.647Z
modified: 2020-11-19T16:21:21.675Z
contributor: AAS Frey.Katie

Stellar spectral lines
type: Concept
broader: Stellar properties

Stellar tracking devices
type: Concept
broader: Astronomical instrumentation
narrower: Siderostats
narrower: Coelostats
narrower: Heliostats

Early-type stars
broader: Stellar types
type: Concept
alternative label: Early type stars
narrower: O stars
narrower: OB stars
narrower: B stars
narrower: Early-type emission stars
narrower: Early-type supergiant stars
narrower: Early-type variable stars
narrower: A stars
narrower: Faint blue stars
contributor: AAS Frey.Katie
alternative label: Hot stars
definition: Hot, luminous stars of spectral type O, B, A, and F0 to F5. They were originally thought, wrongly, to be at an earlier stage of evolution than late-type stars.
modified: 2020-10-30T19:16:42.524Z
editorial note: Definition Provenance
  created: 2020-10-30T19:16:58.001Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-30T19:16:58.030Z

Stellar wind bubbles
type: Concept
alternative label: Interstellar bubbles
alternative label: Stellar-wind bubbles
broader: Interstellar medium
narrower: Heliosphere

Stellar winds
type: Concept
alternative label: Stellar outflows
broader: Stellar-interstellar interactions
broader: Stellar physics
related: Solar wind

Stellar x-ray flares
type: Concept
broader: Stellar flares

Stone circles
type: Concept
broader: Early astronomical instruments
example: Stonehenge
modified: 2022-06-24T17:47:42.113Z
related: Megalithic astronomy
contributor: AAS Frey.Katie Admin

Stratopause
type: Concept
alternative label: Mesopeak
broader: Earth atmosphere
contributor: AAS Frey.Katie Admin
modified: 2020-12-02T22:03:10.202Z

Blazars
type: Concept
broader: Active galactic nuclei
broader: Active galaxies
contributor: AAS Frey.Katie
narrower: Flat-spectrum radio quasars
definition: A term specifying BL Lac objects or quasars when the continuum radiation emitted from the active nucleus is highly polarized and very variable.
modified: 2020-10-26T19:11:27.022Z
modified: 2020-10-26T19:11:38.342Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T19:11:38.312Z

Stratosphere
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: The second major layer of Earth's atmosphere, just above the troposphere and below the mesosphere, extending from about 20 km to 90 km above the Earth. It is characterized by little vertical increase in temperature.
modified: 2020-11-19T16:21:50.413Z
modified: 2020-11-19T16:21:59.903Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:21:59.863Z
  creator: AAS Frey.Katie

Strömgren photometry
type: Concept
alternative label: Four-color photometry
alternative label: Stromgren uvby system
alternative label: Uvby system
broader: Medium band photometry
alternative label: Strömgren photometric system
alternative label: uvbyβ photometric system
contributor: AAS Frey.Katie Admin
alternative label: Stromgren photometry
definition: A four-color stellar photometric system devised by B. Strömgren. It is based on measurements in the ultraviolet (3500 Å), violet (4100 Å), blue (4670 Å), and yellow (5470 Å) regions of the spectrum. The filters bandwidths are 340, 200, 160, and 240 Å respectively. Also known as Strömgren four-color photometry.
modified: 2020-11-04T18:44:57.111Z
modified: 2020-11-04T18:45:12.883Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T18:45:12.848Z

Strömgren spheres
type: Concept
alternative label: Stromgren spheres
broader: Stellar structures
definition: A theoretical sphere of ionized hydrogen created by energetic ultraviolet photons of a hot, massive star embedded in a uniform interstellar molecular cloud and lying at the center of the sphere.
modified: 2020-11-04T18:45:48.932Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T18:46:10.086Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:46:10.116Z

Strong gravitational lensing
type: Concept
broader: Gravitational lensing
modified: 2020-11-19T16:23:01.532Z
contributor: AAS Frey.Katie
definition: A gravitational lensing phenomenon in which the image distortion is strong enough to be readily recognized, such as in the case of the Einstein cross or when giant luminous arcs show up in galaxy clusters (e.g. Abell 2218). Opposite to weak gravitational lensing.
modified: 2020-11-19T16:23:10.708Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:23:10.673Z
  creator: AAS Frey.Katie

Strontium stars
type: Concept
broader: Chemically peculiar stars
broader: Heavy metal stars

SU Ursae Majoris stars
type: Concept
broader: Dwarf novae

Subgiant stars
type: Concept
alternative label: Subgiants
broader: Evolved stars
narrower: O subgiant stars
narrower: B subgiant stars
narrower: F subgiant stars
narrower: G subgiant stars
narrower: A subgiant stars
narrower: K subgiant stars
narrower: M subgiant stars
contributor: AAS Frey.Katie Admin
definition: A star with a lower absolute magnitude than a normal giant star of its spectral type. It is a star that has exhausted the hydrogen at its center and is evolving into a red giant. Subgiants are luminosity class IV.
modified: 2020-11-04T18:48:04.006Z
modified: 2020-11-04T18:48:15.284Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T18:48:15.255Z

Submillimeter astronomy
type: Concept
broader: Radio astronomy
definition: The study of astronomical objects with submillimeter waves. As with millimeter-wave astronomy, this part of the spectrum is rich in lines emitted by interstellar molecules and dust.
modified: 2021-08-24T15:42:39.943Z
preferred label: Submillimetre astronomy
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
modified: 2020-11-19T16:24:28.378Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:24:28.346Z

Summer solstice
type: Concept
broader: Solstice
contributor: AAS Frey.Katie
modified: 2020-11-19T16:24:59.019Z
definition: The moment in the northern hemisphere when the Sun attains its highest declination of 23°26' (or 23°.44) with respect the equator plane. It happens when the Earth's axis is orientated directly toward the Sun, on 21 or 22 June. During the northern solstice the Sun appears to be directly overhead at noon for places situated at latitude 23.44 degrees north, known as the tropic of Cancer. The summer solstice can occur at any moment during the day. Two successive summer solstices are shifted in time by about 6 h. The summer solstice in the northern hemisphere is the winter solstice in the southern hemisphere.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:25:12.756Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:25:12.783Z

Sunspot cycle
type: Concept
broader: Solar cycle
related: Sunspots

Sunspot groups
type: Concept
broader: Sunspots
narrower: Bipolar sunspot groups

Sunspot number
type: Concept
alternative label: Relative sunspot number
alternative label: SSN
alternative label: Wolf number
broader: Sunspots
modified: 2020-11-19T16:25:42.245Z
contributor: AAS Frey.Katie
definition: A quantity which gives the number of sunspots at a given time. It is defined by the relationship R = k(10g + f), where R is the sunspot number, k is a constant depending on the observation conditions and the instrument used, g is the number of the groups and f is the number of individual spots that can be counted.
editorial note: Definition Provenance
  created: 2020-11-19T16:25:52.072Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:25:52.100Z

Sunspots
type: Concept
alternative label: Sun spots
broader: Solar physics
narrower: Maunder minimum
narrower: Sunspot groups
narrower: Sunspot number
narrower: Wilson effect
narrower: Ephemeral active regions
related: Starspots
related: Sunspot cycle
contributor: AAS Frey.Katie Admin
broader: Solar active regions
narrower: Sunspot flow
narrower: Delta sunspots
definition: An area seen as a dark patch on the Sun's surface. Sunspots appear dark because they are cooler (of about 4000 °C) than the surrounding photosphere (about 6000 °C). They range in size from a few hundred kilometers to several times the Earth's diameter and last from a few hours to a few months. Very small sunspots are called pores. The number of sunspots varies from maximum to minimum in about 11 years, the sunspot cycle. Their appearance during a cycle follows the Sporer law. A typical spot has a central umbra surrounded by a penumbra, although either features can exist without the other. Sunspots are associated with strong magnetic fields of 0.2 to 0.4 tesla. A given sunspot has a single magnetic polarity. The opposite polarity may be found in other sunspots or in the bright and diffuse facular region adjacent to the sunspot. The first recorded naked-eye sightings of sunspots were by Chinese astronomers in the first century B.C. Johannes Fabricius (1587-1617) was the first to argue that sunspots are areas on the solar surface.
modified: 2020-12-16T20:39:45.185Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T18:50:12.904Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:50:12.933Z

Super Earths
type: Concept
alternative label: Super-Earths
broader: Exoplanets
definition: An extrasolar planet more massive than the Earth but less massive than 10 Earth masses. The first discovered super-Earth orbits an M4 V star named GJ 876. Its estimated mass is 7.5±0.7 Earth masses and it has an orbital period of 1.94 days. It is close to the host star, and the surface temperature is calculated to lie between 430 and 650 K.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T18:53:34.215Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T18:53:48.428Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:53:48.456Z

Superbubbles
type: Concept
broader: Interstellar medium
definition: A cavity hundreds of light-years across filled with a hot gas blown into the interstellar medium by multiple supernovae and stellar winds. Examples are the Local Bubble in the Orion Arm of the Milky Way and the N44 Superbubble in the Large Magellanic Cloud.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T18:51:03.086Z
editorial note: Definition Provenance
  created: 2020-11-04T18:51:14.812Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:51:14.841Z

Superclusters
type: Concept
broader: Galaxy clusters
narrower: Virgo Supercluster
definition: An aggregation of clusters of galaxies. Superclusters are typically about one hundred million (10^8) light-years in diameter and contain tens of thousands of galaxies. Some examples are the Local Supercluster, Centaurus supercluster, Laniakea supercluster, Perseus-Pisces supercluster, Shapley supercluster, Virgo supercluster.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T18:52:27.103Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T18:52:46.328Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:52:46.355Z

Supergalactic coordinate system
type: Concept
broader: Astronomical coordinate systems
narrower: Supergalactic latitude
narrower: Supergalactic longitude
contributor: AAS Frey.Katie
definition: A spherical coordinate system in which the equator is the supergalactic plane. Supergalactic longitude, SGL, is measured counterclockwise from direction l = 137.37 deg, b = 0 deg (between 0 and 360 deg). The zero point for supergalactic longitude is defined by the intersection of this plane with the Galactic plane. In the equatorial coordinate system (J2000) this is approximately 2.82 h, +59.5 deg. Supergalactic latitude, SGB, is measured from the supergalactic plane, positive northward and negative southward. The North Supergalactic Pole (SGB=90 deg) lies at galactic coordinates l = 47.37 deg, b = +6.32 degrees, corresponding to the equatorial coordinate system (J2000) 18.9 h, +15.7 deg.
modified: 2020-11-19T16:27:39.780Z
editorial note: Definition Provenance
  created: 2020-11-19T16:27:49.427Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:27:49.463Z

Supergalactic latitude
type: Concept
broader: Supergalactic coordinate system

Blue cloud galaxies
type: Concept
broader: Galaxy colors

Supergalactic longitude
type: Concept
broader: Supergalactic coordinate system

Supergiant stars
type: Concept
broader: Evolved stars
narrower: Red supergiant stars
narrower: Early-type supergiant stars
narrower: F supergiant stars
narrower: G supergiant stars
narrower: Late-type supergiant stars
contributor: AAS Frey.Katie Admin
definition: A star with maximum intrinsic brightness and low density. The radius of a supergiant star can be as large as 1000 times that of the Sun.
modified: 2020-11-04T18:55:00.271Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T18:55:12.598Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:55:12.631Z

Supergranulation
type: Concept
broader: Solar granulation

Supermassive black holes
type: Concept
broader: Astrophysical black holes
narrower: Quasars
definition: A black hole of tremendous mass, equivalent to those of millions or even billions of stars, which is believed to exist and occupy the centers of many galaxies. The supermassive black hole residing in the center of our Milky Way Galaxy is the object Sgr A* with a mass of 4 x 10^6 solar masses within a radius of 100 astronomical units.
modified: 2020-11-04T18:56:03.596Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T18:56:23.210Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T18:56:23.242Z

Supernova dynamics
type: Concept
broader: Stellar dynamics
related: Stellar remnants
related: Supernovae
related: Explosive nucleosynthesis

Supernova neutrinos
type: Concept
broader: Particle astrophysics

Supernova remnants
type: Concept
broader: Nebulae
broader: Interstellar medium
definition: The body of expanding gas ejected at a speed of about 10,000 km s^-1 by a supernova explosion, observed as a diffuse gaseous nebula, often with a shell-like structure. Supernova remnants are generally powerful radio sources. The evolution of the SNR can be divided into different phases according to the dominant physical processes. Simplified models are made for the first stages, to get an idea of typical time scales, expansion velocities, and sizes. The three main phases are: 1) the free expansion phase, 2) the Sedov-Taylor phase, and 3) the snowplow phase.
modified: 2020-11-04T19:00:25.918Z
contributor: AAS Frey.Katie Admin
narrower: Pulsar wind nebulae
modified: 2020-11-04T19:00:40.701Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T19:00:40.670Z
  creator: AAS Frey.Katie Admin

Supernovae
type: Concept
broader: Stellar remnants
broader: Stellar types
narrower: Type Ia supernovae
narrower: Core-collapse supernovae
narrower: Hypernovae
related: Supernova dynamics
related: White dwarf stars
related: Burst astrophysics
related: Ejecta
definition: A violent stellar explosion which blows off all or most of the star's material at high velocity leaving a compact stellar remnant such as a neutron star or black hole. At maximum light, the supernova can have luminosity about 108 or 109 times the solar luminosity. The phenomenon results from the later evolution of stars when an instability sets in the core following the nucleosynthesis of iron. In massive stars, the supernova occurs when the star has used up all its available nuclear fuel and it reaches a lower energy state through gravitational collapse to form a more compact object. In white dwarfs forming binary systems, accretion of mass onto the surface of a neutron star can be sufficient to take the star over the upper mass limit for stability as a white dwarf. Consequently, the white dwarf collapses in a supernova explosion to form a neutron star. There are several supernova types.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:08:56.791Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T18:58:21.078Z
modified: 2020-11-04T18:58:21.109Z

Surface gravity
type: Concept
alternative label: Acceleration of gravity
broader: Planetary science
contributor: AAS Frey.Katie
definition: The rate at which a small object in free fall near the surface of a body is accelerated by the gravitational force of the body: g = GM / R^2, where G is the gravitational constant, and M and R are the mass and radius of the object. The surface gravity of Earth is equal to 980 cm s^-2.
modified: 2020-11-19T16:29:42.038Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:29:53.255Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:29:53.283Z

Blue loop
type: Concept
broader: Hertzsprung Russell diagram
contributor: AAS Frey.Katie
definition: An evolutionary behavior of certain stars, particularly massive stars, which return to the blue stage after becoming a red supergiant. The phenomenon appears as a blueward loop on the theoretical evolutionary tracks.
modified: 2020-11-03T17:47:32.056Z
editorial note: Definition Provenance
  created: 2020-11-03T17:47:59.920Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T17:47:59.950Z

Surface photometry
type: Concept
alternative label: Area photometry
broader: Photometry

Surveys
type: Concept
broader: Astronomical reference materials
narrower: Radio source counts
narrower: Redshift surveys
narrower: Sky surveys
narrower: Star counts
narrower: Ultraviolet surveys
narrower: X-ray surveys
narrower: Galaxy counts
narrower: Kapteyn Selected Areas

Symbiotic binary stars
type: Concept
alternative label: Symbiotic binaries
alternative label: Symbiotic stars
broader: Emission line stars
narrower: Symbiotic novae
narrower: Z Andromedae stars
broader: Interacting binary stars
definition: A stellar object whose optical spectrum displays lines characteristic of gases of two very different temperatures, typically of an M star (3500 K) and a B star (20 000 K) superimposed. A symbiotic star is in fact a close binary system.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:06:36.851Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T19:37:32.044Z
modified: 2020-11-04T19:37:32.075Z

Synodic period
type: Concept
broader: Orbital elements
contributor: AAS Frey.Katie
definition: For planets, the mean interval of time between successive conjunctions of two planets, as observed from the Earth. For satellites, the mean interval between successive conjunctions of a satellite with the Sun, as observed from the satellite's primary.
modified: 2020-11-19T16:30:42.222Z
modified: 2020-11-19T16:30:52.146Z
editorial note: Definition Provenance
  created: 2020-11-19T16:30:52.108Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Syzygy
type: Concept
broader: Astrometry
narrower: Occultation
narrower: Transits
narrower: Eclipses
scope note: Conjunction or opposition of planets
modified: 2020-11-19T16:31:29.769Z
contributor: AAS Frey.Katie
definition: The alignment of three or more celestial bodies in the same gravitational system along a nearly straight line. Conjunction or opposition of a heavenly body with the Sun.
editorial note: Definition Provenance
  created: 2020-11-19T16:31:40.293Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:31:40.332Z

T associations
type: Concept
alternative label: T-association
broader: Stellar associations
definition: A stellar association containing many T Tauri stars. Examples include the Taurus-Auriga T association, the nearby TW Hydrae association, and Vela T1 and T2.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T20:29:12.056Z
modified: 2020-11-05T20:29:22.793Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T20:29:22.761Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Brown dwarfs
broader: Stellar evolutionary types
alternative label: Brown dwarf stars
type: Concept
narrower: T dwarfs
narrower: T subdwarfs
narrower: Y dwarfs
narrower: L dwarfs
narrower: L subdwarfs
alternative label: Brown dwarf
definition: A star-like object whose mass is too small to sustain hydrogen fusion in its interior and become a star. Brown dwarfs are substellar objects and occupy an intermediate regime between those of stars and giant planets. With a mass less than 0.08 times that of the Sun (about 80 Jupiter masses), nuclear reactions in the core of brown dwarfs are limited to the transformation of deuterium into Helium-3. The reason is that the cores of these objects are supported against gravitational collapse by electron degeneracy pressure (at early spectral types) and Coulomb pressure (at later spectral types). Brown dwarfs, as ever cooling objects, will have late M dwarf spectral types within a few Myrs of their formation and gradually evolve as L, T and Y dwarfs brown dwarf cooling. As late-M and early-L dwarfs, they overlap in temperature with the cool end of the stellar main sequence (M dwarf, L dwarf, T dwarf, Y dwarf). In contrast to the OBAFGKM sequence, the M-L-T-Y sequence is an evolutionary one.
preferred label: Brown dwarves
contributor: AAS Frey.Katie Admin
modified: 2021-09-27T15:41:15.173Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:23:35.348Z
contributor: AAS Frey.Katie
modified: 2020-10-26T19:23:35.375Z

Blue straggler stars
type: Concept
alternative label: Blue stragglers
related: Yellow straggler stars
alternative label: Blue-straggler stars
broader: Stellar evolutionary types
definition: Any of stars, often found in globular clusters and old open clusters, that lie on the blueward extension of the main sequence beyond the turnoff point. Blue stragglers have an anomalously blue color and high luminosity in comparison with other cluster members. The most probable ways in which they could form are: mass transfer or coalescence in close binary systems, encounters or collisions in overcrowded cores of globular clusters.
contributor: AAS Frey.Katie
modified: 2020-10-26T19:15:28.360Z
modified: 2020-10-26T19:15:39.851Z
editorial note: Definition Provenance
  created: 2020-10-26T19:15:39.822Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

FU Orionis stars
broader: Young stellar objects
related: T Tauri stars
broader: Emission line stars
type: Concept
alternative label: FU Orionis
alternative label: FU-Orionis
broader: Flare stars
related: Infrared sources
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:46:11.544Z

Tailed radio galaxies
type: Concept
alternative label: Head tail galaxies
broader: Radio galaxies
contributor: AAS Frey.Katie Admin
alternative label: Head-tail galaxies
definition: A member of the class of radio galaxies that have a strong radio emission coming from a bright 'head' and a more diffuse emission from a 'tail.' They are often found in clusters.
modified: 2020-11-04T19:49:10.435Z
modified: 2020-11-04T19:49:24.541Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T19:49:24.515Z
  creator: AAS Frey.Katie Admin

Technetium stars
type: Concept
broader: Chemically peculiar stars
broader: Heavy metal stars

Astronomical techniques
type: Concept
alternative label: Observation techniques
broader: Observational astronomy
narrower: Optical observation
narrower: Photometry
narrower: Pointing accuracy
narrower: Polarimetry
narrower: Spectroscopy
narrower: CCD observation
narrower: Coronagraphic imaging
narrower: Doppler imaging
narrower: Doppler shift
narrower: Drift scan imaging
narrower: Field of view
narrower: High time resolution astrophysics
narrower: Astrometry
narrower: Interferometry
narrower: Astronomical object identification
narrower: Astronomical optics
narrower: Direct imaging
alternative label: Techniques
narrower: Analytical mathematics
narrower: Reverberation mapping
narrower: Scaling relations
narrower: Faber-Jackson distance
contributor: AAS Frey.Katie Admin
narrower: Magnetospheric radio emissions
narrower: High angular resolution
narrower: Calibration
narrower: Remote sensing
narrower: Mass spectrometry
modified: 2022-06-11T21:53:05.143Z
narrower: Magnetogram

Tektites
type: Concept
broader: Meteorites
narrower: Moldavites
narrower: Australites
narrower: Bediasites
narrower: Indochinites
definition: Small glassy bodies whose chemical composition is unrelated to the geological formation in which they are found. They are found mostly in Australia, Java, Philippines and Indochina. Tektites are now thought to have been produced by the impact of meteorites on the earth's surface.
modified: 2020-11-04T19:51:02.987Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T19:51:14.249Z
modified: 2020-11-04T19:51:14.278Z

Telescope focal plane photography
type: Concept
broader: Astrophotography

Telescope mounts
type: Concept
alternative label: Telescope mountings
broader: Telescopes
narrower: Alt-azimuth mounts
narrower: Equatorial mounts

Telescopes
type: Concept
broader: Astronomical instrumentation
narrower: Meridian circles
narrower: Neutrino telescopes
narrower: Optical telescopes
narrower: Automated telescopes
narrower: Radio telescopes
narrower: Solar telescopes
narrower: Space telescopes
narrower: Telescope mounts
narrower: Wide-field telescopes
narrower: Grazing incidence telescopes
narrower: Ground telescopes
contributor: AAS Frey.Katie Admin
narrower: Gamma-ray telescopes
modified: 2020-11-24T17:29:34.053Z
definition: An instrument used to collect and amplify light or other energy. Refracting telescopes gather light by means of a lens, reflecting telescopes by means of a mirror. Radio telescopes gather radio energy by using an antenna. Telescopes have also been built that can gather X rays, gamma rays, and other forms of energy.
narrower: Telescope properties
modified: 2020-11-04T19:52:30.277Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T19:52:30.235Z

Blueshifted
type: Concept
alternative label: Blue shift
alternative label: Blueshift
broader: Doppler shift
definition: The apparent shift of the wavelength towards the shorter wavelength region of the radiation spectrum of an approaching object due to the Doppler effect.
modified: 2020-11-04T20:46:37.113Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T20:46:50.240Z
editorial note: Definition Provenance
  created: 2020-11-04T20:46:50.209Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Termination shock
type: Concept
broader: Heliosphere
contributor: AAS Frey.Katie
definition: A shock wave inside the heliopause where the supersonic solar wind abruptly slows from an average speed of 500 km s^-1 to subsonic and becomes denser and hotter.
modified: 2020-11-19T16:34:10.323Z
modified: 2020-11-19T16:34:19.653Z
editorial note: Definition Provenance
  created: 2020-11-19T16:34:19.626Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Tertiary stars
type: Concept
broader: Companion stars

The Moon
type: Concept
alternative label: Earth's Moon
alternative label: Luna
broader: Natural satellites (Solar system)
broader: Solar system
related: Lunar science
contributor: AAS Frey.Katie
related: Earth (planet)
definition: Natural satellite of the Earth. Mass 7.35 x 10^25 g = 1/81 or 0.0123 Earth's. Mean radius 1740 km = ~ 1/4 the Earth's; this relatively small size ratio makes the Earth-Moon system unique in the solar system. Mean density 3.34 g cm-3. Mean distance from Earth 384,400 km. Escape velocity 2.38 km s-1. Surface gravity 162.2 cm s-2 = 0.165 Earth's. Sidereal period 27d 7h 43m 11s. Eccentricity 0.0549. Inclination of orbital plane to ecliptic 5° 8' 43''. Obliquity 6° 41'. Synodic period 29d 12h 44m 2s.9. Orbital velocity 1.02 km s-1. The Moon's average visual albedo is 0.12, a factor of three smaller than that of Earth. The Moon's center of mass is displaced about 2 km in the direction of Earth. The average temperature on the surface of the Moon during the day is 107 °C. During the night, the average temperature drops to -153 °C. Studies of lunar rock have shown that melting and separation must have begun at least 4.5 x 109 years ago, so the crust of the Moon was beginning to form a very short time after the solar system itself. Thickness of crust ~ 60 km; of mantle ~ 1000 km. Temperature of core ~ 1500 K. It would have taken only 107 years to slow the Moon's rotation into its present lock with its orbital period. Because of this synchronous rotation, the Moon revolves once on its axis each time it orbits the Earth, thus always presenting the same face, the nearside, toward Earth. The Moon may have formed during a collision between the early Earth and a Mars-sized rocky planet about 4.6 billion years ago; Theia.
modified: 2020-11-19T16:35:04.040Z
modified: 2020-11-19T16:35:13.351Z
editorial note: Definition Provenance
  created: 2020-11-19T16:35:13.326Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

The Sun
type: Concept
broader: Solar system
related: Solar physics
related: Solar analogs
contributor: AAS Frey.Katie
definition: The star that governs the solar system. It is a yellow main-sequence star of spectral type G2, shines with apparent magnitude -26.74, and has an absolute magnitude of +4.83. The Sun is 4.6 billion years old and lies 27,000 light-years from the Galactic center.
modified: 2020-11-19T16:35:54.502Z
modified: 2020-11-19T16:36:04.115Z
editorial note: Definition Provenance
  created: 2020-11-19T16:36:04.083Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Thermosphere
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: The region of the upper atmosphere in which temperature increases continuously with height, starting at roughly 100 km. The thermosphere includes the exosphere and most of the ionosphere.
modified: 2020-11-19T16:36:35.857Z
modified: 2020-11-19T16:36:49.915Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:36:49.884Z

Three-body problem
type: Concept
alternative label: Three body problem
broader: Celestial mechanics
broader: Gravitational interaction
narrower: Mass ratio
narrower: Roche limit
narrower: Roche lobe
narrower: Lagrangian points
contributor: AAS Frey.Katie
definition: The mathematical problem of studying the positions and velocities of three mutually attracting bodies (such as the Sun, Earth and Moon) and the stability of their motion. This problem is surprisingly difficult to solve, even in the simple case, called restricted three-body problem, where one of the masses is taken to be negligibly small so that the problem simplifies to finding the behavior of the mass-less body in the combined gravitational field of the other two.
modified: 2020-11-19T16:37:16.341Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:37:27.660Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:37:27.697Z

Tidal disruption
type: Concept
alternative label: Tidal filament hypothesis
broader: Tidal interaction
broader: Gravitational disruption
contributor: AAS Frey.Katie
definition: The disruption of an extended astronomical object under the action of the tidal forces exerted by another nearby object.
modified: 2020-11-19T16:37:56.271Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:38:05.690Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:38:05.712Z

Tidal distortion
type: Concept
alternative label: Tidal bulge
broader: Tidal interaction

Tidal friction
type: Concept
broader: Tidal interaction
contributor: AAS Frey.Katie
definition: The friction exerted on a primary body (Earth) because of the phase lag between the tides and the gravitational attraction of the secondary body (Moon). The Earth's rotation is faster than the Moon's orbital motion; therefore the Earth's tidal bulges lead the Moon on its orbit. This has two important effects: The Earth is being pulled slightly 'back' from its sense of rotation. So the Earth's rotation slows (by about 1 second every 50,000 years). Moreover, the Moon is being pulled slightly 'forward' on its orbit. So it is harder for the Earth to hold it in place, and it moves further away from the Earth (by about 3-4 cm per yr). Tidal friction tends to synchronize the rotation period of a close-in companion with the period of its orbital motion around the primary.
modified: 2020-11-19T16:38:45.291Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:38:57.597Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:38:57.623Z

Tidal interaction
type: Concept
broader: Gravitational interaction
narrower: Roche limit
narrower: Tidal disruption
narrower: Tidal distortion
narrower: Tidal friction
narrower: Tidal radius
narrower: Tides

Active galaxies
type: Concept
broader: Galaxies
narrower: Markarian galaxies
narrower: Radio galaxies
narrower: Starburst galaxies
narrower: BL Lacertae objects
narrower: Active galactic nuclei
narrower: Blazars
narrower: Haro galaxies
narrower: LINER galaxies
narrower: AGN host galaxies
contributor: AAS Frey.Katie
definition: A galaxy that produces huge amounts of energy at its center, which cannot be attributed to normal processes from stars, interstellar medium, and their interactions. There are several types of active galaxies: Seyfert galaxies, quasars, and blazars. All of these objects show brightness variations, some as short as 3 hours. These fluctuations indicate a relatively very small size for the central object, because an object cannot vary in brightness faster than light can travel across it. For example, an object that is one light-year in diameter cannot vary significantly in brightness over a period of less than one year.
modified: 2020-11-03T17:54:29.591Z
editorial note: Definition Provenance
  created: 2020-11-03T17:54:46.141Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T17:54:46.169Z

Bode's law
type: Concept
alternative label: Bodes law
alternative label: Titius-Bode law
broader: Orbital theory
contributor: AAS Frey.Katie
definition: The empirical rule relating the approximate distances of the solar system planets from the Sun. The original formulation was: a = (n + 4) / 10, where a is the mean distance of a planet from the Sun in astronomical units and n = 0, 3, 6, 12, 24, 48, 96, 192 (doubling for each successive planet). The planets were seen to fit this sequence quite well, provided the asteroids between Mars and Jupiter are counted as one planet, as did Uranus discovered in 1781. However, Neptune and the ex-planet Pluto do not conform to the rule. The question of whether there is any physical significance to the 'law,' i.e. some dynamical reason that will explain planetary orbit spacing has led to much discussion during the past two centuries. Today, many astronomers are very skeptical and consider this 'law' to be numerical coincidence.
modified: 2020-11-03T18:52:05.208Z
editorial note: Definition Provenance
  created: 2020-11-03T18:52:18.882Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:52:18.910Z

Tidal radius
type: Concept
broader: Tidal interaction

Tidal tails
type: Concept
broader: Interstellar medium
broader: Galaxy tails
modified: 2020-11-04T19:50:18.651Z
definition: A long stream of stars and gas, often in the form of a spectacular tail, thrown off a galaxy when it collides with another galaxy. Two tidal tails form in each galaxy, and they are more spectacular when the masses of the two galaxies are comparable, and when their relative orbit is in the same sense as the rotation inside each spiral galaxy.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T19:50:30.842Z
editorial note: Definition Provenance
  created: 2020-11-04T19:50:30.819Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Tides
type: Concept
broader: Tidal interaction
narrower: Ocean tides
narrower: Atmospheric tides
narrower: Solid body tides

Timing variation methods
type: Concept
broader: Exoplanet detection methods
narrower: Pulsar timing method
narrower: Pulsation frequency method
narrower: Transit duration variation method
narrower: Transit timing variation method
narrower: Eclipsing binary minima timing method

Total eclipses
type: Concept
broader: Eclipses
definition: An eclipse in which the whole of the disk of the Sun or Moon is obscured.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T19:55:40.013Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T19:55:52.281Z
modified: 2020-11-04T19:55:52.311Z

Trans-Neptunian objects
type: Concept
alternative label: Kuiper belt objects
alternative label: TNO
alternative label: Trans Neptunian objects
alternative label: Transneptunian objects
broader: Kuiper belt
narrower: Neptune trojans
narrower: Plutoids
narrower: Resonant Kuiper belt objects
narrower: Classical Kuiper belt objects
narrower: Detached objects
contributor: AAS Frey.Katie Admin
broader: Small Solar System bodies
alternative label: Trans–Neptunian objects
modified: 2024-02-21T20:27:14.885Z

Trans-Planckian physics
type: Concept
broader: Black hole physics

Transit duration variation method
type: Concept
broader: Timing variation methods

Transit instruments
type: Concept
broader: Astronomical instrumentation
narrower: Meridian circles
narrower: Zenith telescopes
narrower: Zenith tubes
definition: An instrument mounted so as to allow it to be pointed only at objects in the sky crossing the local meridian. Also known as transit telescopes.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T22:01:56.422Z
alternative label: Transit telescopes
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T22:02:15.348Z
modified: 2020-11-04T22:02:15.377Z

Bok globules
type: Concept
broader: Protostars
broader: Dark interstellar clouds
broader: H II regions

Transit timing variation method
type: Concept
broader: Timing variation methods

Transits
type: Concept
alternative label: Astronomical transits
broader: Syzygy
related: Occultation
definition: An event where one astronomical object appears to move across the face of another. As seen from Earth, the planets Venus and Mercury are seen to transit the Sun. We can also observe natural satellites transit the face of their host planet. Similarly exoplanets have been observed to transit their host stars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T22:00:14.615Z
modified: 2020-11-04T22:00:29.260Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T22:00:29.227Z
  creator: AAS Frey.Katie Admin

Triangulum Galaxy
type: Concept
alternative label: M33
alternative label: Messier 33
alternative label: NGC 598
broader: Spiral galaxies
broader: Local Group
contributor: AAS Frey.Katie Admin
modified: 2020-12-17T17:10:20.951Z
definition: One of the prominent members of the Local Group situated in the constellation Triangulum. Also known as NGC 598. M33 is a type Sc spiral galaxy seen nearly face-on. It lies 2.8 million light-years away and its diameter is 52,000 light-years. M33 is thought to be a satellite of the Andromeda Galaxy.
editorial note: Definition Provenance
  created: 2020-11-04T21:59:08.635Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T21:59:08.666Z

Trigonometric parallax
type: Concept
broader: Parallax
contributor: AAS Frey.Katie
definition: The parallax of a nearby star (less than 300 light-years) against the background of more distant stars resulting from the motion of the Earth in its orbit around the Sun.
modified: 2020-11-19T16:41:14.798Z
modified: 2020-11-19T16:41:24.321Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T16:41:24.291Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Trinary stars
type: Concept
alternative label: Ternary stars
alternative label: Triple stars
broader: Multiple stars
example: Polaris
contributor: AAS Frey.Katie Admin
modified: 2022-06-24T15:30:14.016Z

Trojan asteroids
type: Concept
alternative label: Trojan group
alternative label: Trojans
broader: Asteroids
narrower: Mars trojans
narrower: Neptune trojans
narrower: Earth trojans
narrower: Jupiter trojans
definition: A member of the family of asteroids that share Jupiter's orbit and lie in elongated, curved regions around the two Lagrangian points 60° ahead and behind of Jupiter. The Lagrangian points L4 and L5 host several thousands of them. Originally, the term Trojan applied only to asteroids sharing Jupiter's orbit; however, planetoidal bodies have been discovered at the Lagrangian points of Mars and Neptune as well, and are also referred to as Mars Trojans and Neptune Trojans respectively.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:57:14.012Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:57:26.761Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T21:57:26.793Z

Trojan planets
type: Concept
broader: Exoplanets

Tropopause
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: The boundary between the troposphere and stratosphere. Its height, varying with latitude and seasons, is from 8 km at poles, to 18 km at equator; it is higher during winter time. The atmospheric temperature decreases from ground upward until the tropopause. Then it increases in stratosphere because of the absorption of solar ultraviolet radiation.
modified: 2020-11-19T16:42:14.328Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:42:24.489Z
modified: 2020-11-19T16:42:24.522Z

Troposphere
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: The lower part of the Earth's atmosphere in which temperature decreases with height, except for local areas of temperature inversion.
modified: 2020-11-19T16:42:53.638Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:43:03.832Z
modified: 2020-11-19T16:43:03.864Z

True anomaly
type: Concept
broader: Orbital anomalies
modified: 2020-11-19T16:43:29.981Z
contributor: AAS Frey.Katie
definition: One of the standard orbital elements, which is the angle measured at the focus nearest the periapsis of an elliptical orbit, between the periapsis and the radius vector from the focus to the orbiting body.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:43:39.564Z
modified: 2020-11-19T16:43:39.594Z

Bolides
type: Concept
broader: Fireballs
contributor: AAS Frey.Katie
definition: A meteor which is extremely bright, particularly one that breaks up during its passage through the atmosphere.
modified: 2020-10-26T19:20:10.403Z
modified: 2020-10-26T19:20:23.975Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:20:23.950Z

True position
type: Concept
broader: Astronomical location
contributor: AAS Frey.Katie
definition: The coordinates of an object for a given date, with respect to the true equator and the true equinoxes for the instant of time in question.
modified: 2020-11-19T16:44:03.640Z
modified: 2020-11-19T16:44:12.833Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:44:12.800Z

Turnoff point
type: Concept
broader: Hertzsprung Russell diagram
contributor: AAS Frey.Katie
definition: The point on the Hertzsprung-Russell diagram of a star cluster at which stars begin to leave the main sequence and move toward the red giant branch. The main-sequence turnoff is a measure of age. In general, the older a star cluster, the fainter the main-sequence turnoff.
modified: 2020-11-19T16:44:37.661Z
modified: 2020-11-19T16:44:48.440Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:44:48.407Z
  creator: AAS Frey.Katie

Twilight
type: Concept
broader: Sky brightness
contributor: AAS Frey.Katie
definition: The diffused light from the sky when the Sun is below the horizon, either from daybreak to sunrise or, more commonly, from sunset to nightfall. There are three types of twilight: astronomical twilight, civil twilight, and nautical twilight. They are divided on the basis of the solar depression angle.
modified: 2020-11-19T16:45:13.874Z
modified: 2020-11-19T16:45:23.509Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:45:23.475Z

Two-body problem
type: Concept
alternative label: Two body problem
broader: Celestial mechanics
broader: Gravitational interaction
contributor: AAS Frey.Katie
definition: In classical mechanics, the study concerned with the dynamics of an isolated system of two particles subject only to the Newtonian gravitational force between them. The problem can be separated into two single-particle problems with the following solutions. The equation of the center of mass is governed by the equation of the same form as that for a single particle. Moreover, the motion of either particle, with respect to the other as origin, is the same as the motion with respect to a fixed origin of a single particle of reduced mass acted on by the same internal force.
modified: 2020-11-19T16:45:50.315Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:45:59.481Z
modified: 2020-11-19T16:45:59.508Z

Two-color diagrams
type: Concept
alternative label: Color-color diagrams
alternative label: Two color diagrams
broader: Photometry
broader: Apparent magnitude
broader: Astrometry
definition: A graph on which two color indices such as B-V and U-B are plotted, one along each axis, for a sample of stars or other objects, such as stars.
contributor: AAS Frey.Katie Admin
preferred label: Two-colour diagrams
modified: 2021-08-24T15:21:16.154Z
modified: 2020-11-04T21:56:28.021Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:56:27.990Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Two-dimensional gravity
type: Concept
alternative label: 2D gravity
alternative label: Two dimensional gravity
broader: Non-standard theories of gravity

Twotinos
type: Concept
broader: Resonant Kuiper belt objects

Type Ia supernovae
type: Concept
alternative label: Type Ia supernova
broader: Supernovae
related: White dwarf stars
contributor: AAS Frey.Katie Admin
definition: A Type I supernova that presents a singly-ionized silicon (Si II) absorption feature at 6150 Å near peak brightness. Type Ia SNe are believed to result from mass accretion to a carbon-oxygen white dwarf in a close binary system. When the white dwarf mass exceeds the Chandrasekhar limit, the degenerate electron pressure can no longer support the accumulated mass and the star collapses in a thermonuclear explosion producing a supernova. The peak luminosity of SNe Ia is set by the radioactive decay chain, and the observed photometric correlation between the peak luminosity and the time-scale over which the light curve decays from its maximum is understood physically as having both the luminosity and opacity being set by the mass of Nickel-56 synthesized in the explosion. Type Ia supernovae occur in all types of galaxies. Type Ia SNe are used as standard candles in determining cosmological distances, after normalizing their light curves with the Phillips relation.
modified: 2020-11-04T21:47:16.570Z
editorial note: Definition Provenance
  created: 2020-11-04T21:47:27.529Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T21:47:27.563Z

Type Ib supernovae
type: Concept
broader: Core-collapse supernovae
definition: A Type I supernova that has neutral helium line (He I) at 5876 Å, and no strong silicon (Si II) absorption feature at 6150 Å. Type Ib supernovae are believed to result from the evolution of massive stars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:47:46.652Z
modified: 2020-11-04T21:47:57.807Z
editorial note: Definition Provenance
  created: 2020-11-04T21:47:57.779Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Bolometric correction
type: Concept
broader: Astrometry
contributor: AAS Frey.Katie
definition: The difference between the visual magnitude and bolometric magnitude.
modified: 2020-11-03T18:53:11.378Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:53:22.518Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:53:22.541Z

Type Ic supernovae
type: Concept
broader: Core-collapse supernovae
contributor: AAS Frey.Katie Admin
definition: A Type I supernova that shows weak or no helium lines and no strong silicon (Si II) absorption feature near 6150 Å. Type Ic supernovae are believed to result from the evolution of massive stars.
modified: 2020-11-04T21:48:15.665Z
modified: 2020-11-04T21:48:27.064Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:48:27.028Z
  creator: AAS Frey.Katie Admin

Type II supernovae
type: Concept
broader: Core-collapse supernovae
related: Chandrasekhar limit
definition: A supernova type whose spectrum contains hydrogen lines. Compared with Type I supernovae, its light curve has a broader peak at maximum and dies away more rapidly. The magnitudes are smaller, ranging from M_V = -12 to -13.5, and the ejecta have lower velocities (about 5,000 km/sec). These supernovae, which result from the final evolution of massive stars, have three main divisions: Type II-P, Type II-L, and Type II-n.
modified: 2020-11-04T21:44:53.439Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:45:08.134Z
editorial note: Definition Provenance
  created: 2020-11-04T21:45:08.109Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

U Geminorum stars
type: Concept
alternative label: SS cygni stars
broader: Dwarf novae

Ultra-high-energy cosmic radiation
type: Concept
alternative label: Ultra high energy cosmic radiation
alternative label: Ultra high energy cosmic rays
alternative label: Ultra-high-energy-cosmic rays
broader: Cosmic rays
definition: A particle belonging to the most energetic population of cosmic rays with an energy above ~10^20 electron-volts. The UHECRs constitute a real challenge for theoretical models, because their acceleration requires extreme conditions hardly fulfilled by known astrophysical objects.
modified: 2020-11-04T21:41:58.592Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:42:11.607Z
editorial note: Definition Provenance
  created: 2020-11-04T21:42:11.573Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Ultracompact dwarf galaxies
contributor: AAS Frey.Katie Admin
type: Concept
broader: Compact dwarf galaxies
definition: A type of very bright compact stellar system (-14 ≤ MV ≥ -12) that is intermediate between globular clusters (GCs) and compact elliptical galaxies (cEs). With masses of M > 2 x 10^6 M_sun and radii > 10 parsecs (pc), UCDs are among the densest stellar systems in the Universe. Nevertheless, the nature and origin of these objects is still widely debated. Early interpretations suggested that UCDs could be the most massive GCs or possibly the tidally stripped remnants of dwarf galaxies. However, there is evidence that both formation mechanisms could contribute to the UCD population. Supermassive black holes (SMBHs) have been confirmed in most UCDs with masses M > 10^7 M_sun. The most massive UCD discovered to date, M59-UCD3 (M_* ~2 x 10^8 M_sun, radius ~ 25 pc), hosts a SMBH.
modified: 2020-11-24T17:15:25.493Z
editorial note: Definition Provenance
  created: 2020-11-04T21:43:40.491Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T21:43:40.520Z

Ultraluminous infrared galaxies
type: Concept
alternative label: ULIRG
broader: Infrared galaxies
definition: A galaxy that emits more than 90% of its energy in the infrared (8-1000 µm) and whose infrared luminosity exceeds 10^12 solar luminosities. Quasars can also have such high or even higher bolometric luminosities. However LIRGs and ULIRGs emit the bulk of their energy in the infrared. Most of ULIRGs are found in merging and interacting galaxy systems. It is thought that their luminosity results from galactic collisions, which increase the rate of star formation.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:39:25.479Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:39:37.525Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T21:39:37.553Z

Ultraviolet astronomy
type: Concept
alternative label: UV astronomy
broader: Astronomical methods
narrower: Near ultraviolet astronomy
related: Ultraviolet sources
contributor: AAS Frey.Katie
modified: 2020-11-19T16:49:13.943Z
narrower: Extreme ultraviolet astronomy
definition: The study of astronomical objects in the ultraviolet portions of the electromagnetic spectrum, in the waveband 3000 Å to about 10 Å. At these wavelengths, the atmosphere prevents ultraviolet radiation from reaching the Earth surface. Therefore ground-based observatories cannot observe in the ultraviolet. Only with the advent of space-based telescopes has this area of astronomy become available for research.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:49:23.840Z
  creator: AAS Frey.Katie
modified: 2020-11-19T16:49:23.868Z

Ultraviolet color
type: Concept
preferred label: Ultraviolet colour
broader: Ultraviolet photometry
modified: 2021-08-24T15:21:38.542Z
contributor: AAS Frey.Katie Admin

Ultraviolet extinction
type: Concept
broader: Atmospheric extinction
scope note: In earth's atmosphere

Ultraviolet observatories
type: Concept
broader: Observatories
narrower: Hubble Space Telescope

Bondi accretion
type: Concept
broader: Accretion
alternative label: Bondi-Hoyle accretion
contributor: AAS Frey.Katie Admin
definition: The accretion of mass by a star (assumed as point particle) moving at a steady speed through an infinite, uniform gas cloud. It is directly proportional to the star mass (M) and the medium density (ρ) and inversely proportional to the relative star/gas velocity (v).
modified: 2020-11-04T22:08:02.836Z
modified: 2020-11-04T22:08:12.601Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T22:08:12.567Z

Ultraviolet photometry
type: Concept
broader: Waveband photometry
narrower: Ultraviolet color

Ultraviolet surveys
type: Concept
broader: Surveys

Ultraviolet telescopes
type: Concept
alternative label: UV telescopes
broader: Space telescopes

Umbra
type: Concept
broader: Eclipses
contributor: AAS Frey.Katie
definition: A dark area, especially the blackest part of a shadow from which all light is cut off.
modified: 2020-11-19T16:49:57.642Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T16:50:12.167Z
modified: 2020-11-19T16:50:12.195Z

Unbarred spiral galaxies
type: Concept
alternative label: SA galaxies
broader: Spiral galaxies

Uncharged black holes
type: Concept
broader: Classical black holes
narrower: Schwarzschild black holes
narrower: Kerr black holes

Underabundances
type: Concept
broader: Chemical abundances
definition: The abundance of a chemical element being lower than a reference value, in particular compared to that of the Sun.
modified: 2020-11-04T21:37:16.143Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:37:27.966Z
editorial note: Definition Provenance
  created: 2020-11-04T21:37:27.933Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Upper atmosphere
type: Concept
broader: Planetary atmospheres
scope note: Earth's atmosphere
contributor: AAS Frey.Katie
definition: The general term applied to the atmosphere above the troposphere.
modified: 2020-11-19T16:50:53.207Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:51:02.523Z
  creator: AAS Frey.Katie
modified: 2020-11-19T16:51:02.566Z

Upsilon Sagittarii stars
type: Concept
broader: Eclipsing binary stars

Uranian satellites
type: Concept
alternative label: Moons of Uranus
alternative label: Oberon
alternative label: Titania
alternative label: Uranian moons
broader: Natural satellites (Solar system)
related: Uranus
example: Titania
contributor: AAS Frey.Katie Admin
example: Oberon
example: Ariel
example: Umbriel
modified: 2020-12-09T15:21:17.240Z

Uranus
type: Concept
broader: Solar system gas giant planets
contributor: AAS Frey.Katie
related: Uranian satellites
definition: The seventh planet from the Sun and the third largest, discovered by William Herschel in 1781. It has a diameter about 51,100 km, four times that of the Earth, and a mass 14.5 times Earth's mass. Uranus orbits the Sun at a distance over 19 times the Earth-Sun distance. Although it takes about 84 years for Uranus to make a revolution, it completes a fast rotation in only 17 and a half hours. Unlike the other planets, its axis of rotation lies mostly in the plane of the Solar System. Uranus is internally less active than the other giant planets, which added to its larger distance from the Sun, makes it colder. It has a dense atmosphere made of mostly molecular hydrogen (83 percent) and helium (15 percent), with two percent methane and traces of acetylene and other hydrocarbons. The planet's greenish-blue color is due to light scattering as in Earth's sky and the absorption of red light by its small amount of atmospheric methane. Uranus has a ring system and 27 known satellites.
modified: 2020-11-19T16:51:37.124Z
modified: 2020-11-19T16:51:47.846Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:51:47.819Z
  creator: AAS Frey.Katie

Urca process
type: Concept
broader: Neutrino astronomy
broader: Particle astrophysics
contributor: AAS Frey.Katie
definition: A cycle of nuclear reactions, primarily among the iron group of elements, accompanied by a high rate of neutrino formation. Neutrinos carry away energy quickly leading to the cooling of the stellar core and a dramatic drop in the pressure. Due to this process in pre-supernova stars, the core becomes unable to support the weight of the overlying layers. These layers collapse onto the core and subsequently rebound and escape in the supernova explosion.
modified: 2020-11-19T16:52:13.894Z
editorial note: Definition Provenance
  created: 2020-11-19T16:52:23.664Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:52:23.706Z

Ursa Minor dwarf spheroidal galaxy
type: Concept
broader: Dwarf spheroidal galaxies

UV Ceti stars
type: Concept
alternative label: UV Ceti
alternative label: UV-Ceti
broader: Flare stars
related: Variable radiation sources

UV Persei stars
type: Concept
broader: Cataclysmic variable stars

UX Ursae Majoris stars
type: Concept
broader: Nova-like variable stars

Van Allen radiation belts
type: Concept
alternative label: Radiation belts
broader: Planetary magnetospheres
alternative label: Van Allen belts
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:35:50.051Z
definition: The ring-shaped regions of charged particles surrounding the Earth from 1 to 6 Earth radii into space. The charged particles are trapped in by the Earth's magnetic field. The inner belt is between 1.2 and 4.5 Earth radii and contains high-energy electrons and protons which originate mainly from interactions between cosmic rays and the upper atmosphere. The outer belt, located between 4.5 and 6.0 Earth radii, contains lower-energy charged particles mainly coming from the solar wind.
modified: 2020-11-04T21:36:01.728Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:36:01.697Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Variable radiation sources
type: Concept
broader: Astronomical radiation sources
related: UV Ceti stars

Variable star period change
type: Concept
alternative label: Period variation
alternative label: Period-change
alternative label: Periodically variable
alternative label: Periodically-variable
broader: Apparent magnitude

Variable stars
narrower: Peculiar variable stars
type: Concept
alternative label: Variables
broader: Stellar types
narrower: Periodic variable stars
narrower: Extrinsic variable stars
narrower: Intrinsic variable stars
related: Purkinje effect
related: Kappa mechanism
contributor: AAS Frey.Katie
related: Time domain astronomy
modified: 2019-11-25T18:32:59.659Z

Venus
type: Concept
broader: Solar system terrestrial planets
definition: The second planet from the Sun, at a mean distance of roughly 108.21 x 10^6 km (0.72 astronomical units). The greatest elongation of Venus is about 47°, making it visible at most about 3 hours after sunset or before sunrise. Venus has the most circular orbit of any planet in the solar system. Venus is only slightly smaller than Earth (95% of Earth's diameter, 80% of Earth's mass). Its chemical composition and density are comparable to those of the Earth. It takes Venus just under 224.401 days to orbit the Sun, compared to the 365 day orbital period of the Earth. Venus' rotation is retrograde, that is it actually rotates from east to west, as opposed to west to east (prograde) which is the common rotating direction of most other planets. Seen from Venus, the sun would rise in the west and set in the east. Moreover, it takes about 244 Earth days for Venus to rotate once (sidereal rotation). This is longer than its orbital period. The length of its solar day is about 117 Earth days. Venus rotation. Its axial tilt is only three degrees, so there are no seasons on Venus. The atmosphere on the surface of Venus consists mostly of carbon dioxide, with a small trace of nitrogen. Venus has a surface pressure about 90 times that of the Earth.
modified: 2020-11-24T17:07:10.206Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-19T16:53:19.889Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:53:19.920Z
contributor: AAS Frey.Katie

Vernal equinox
type: Concept
broader: Equinox
contributor: AAS Frey.Katie
definition: The point of intersection between the ecliptic and the celestial equator at which the Sun passes from south to north of the celestial equator during its apparent annual motion. The instant of this event. It occurs on March 20, 21 or rarely 19. At the vernal equinox, as with the autumnal equinox, night and day are equal in length world over. Several thousands years ago the vernal equinox was in Aries, but because of precession it has now slid west into Pisces. Right ascension and celestial longitude are measured from the vernal equinox.
modified: 2020-11-19T16:53:52.247Z
editorial note: Definition Provenance
  created: 2020-11-19T16:54:01.728Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:54:01.756Z

Vertical circle
type: Concept
broader: Horizontal coordinate system
contributor: AAS Frey.Katie
definition: The greater circle on the celestial sphere which passes through zenith, nadir, and the star and whose plane is perpendicular to the plane of horizon.
modified: 2020-11-19T16:54:29.071Z
editorial note: Definition Provenance
  created: 2020-11-19T16:54:39.466Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:54:39.495Z

Very Large Array
type: Concept
alternative label: VLA
broader: Radio interferometers
definition: A radio interferometer consisting of 27 antennas, each 25 m in diameter, in a Y-shaped configuration. It is located about 100 km west of Socorro, New Mexico, and is operated by the United States National Radio Astronomy Observatory. The VLA has the resolution of a single antenna 36 km wide and the sensitivity of a dish 130 m across.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:28:18.823Z
modified: 2020-11-04T21:28:34.817Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:28:34.790Z

Very Large Telescope
type: Concept
alternative label: VLT
definition: An observing facility consisting of four 8.2 m telescopes, with the combined collecting area of a 16 m mirror, owned and operated by the European Southern Observatory at an altitude of 2635 m at the Paranal Observatory in Chile. The four reflecting unit telescopes are called Antu 'Sun' in the language of Chile's indigenous Mapuche people, Kueyen 'Moon,' Melipal 'Southern Cross,' and Yepun 'Venus.' Each unit is equipped with several sophisticated instruments. The light of the individual telescopes can be combined using interferometric techniques to achieve superior resolution. The wavelength range covered by the VLT is extremely wide, ranging from deep ultraviolet to mid-infrared.
contributor: AAS Frey.Katie Admin
broader: Optical observatories
modified: 2022-06-21T20:05:23.959Z
modified: 2020-11-04T21:29:36.828Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:29:36.792Z

Very long baseline interferometers
type: Concept
alternative label: VLB arrays
broader: Radio interferometers
related: Very long baseline interferometry

Very long baseline interferometry
type: Concept
alternative label: VLB interferometry
alternative label: VLBI
broader: Radio interferometry
related: Very long baseline interferometers
contributor: AAS Frey.Katie
definition: A technique in radio interferometry in which the individual telescopes are not directly connected together, but instead make their observations separately with very accurate timings. The data are later sent to a central correlator to be combined. With this technique the individual telescopes can be arbitrarily far apart, and so the technique provides the highest resolution images in astronomy, typically down to a few milliarcseconds.
modified: 2020-11-19T16:55:46.453Z
editorial note: Definition Provenance
  created: 2020-11-19T16:55:57.189Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:55:57.216Z

Bouwers telescope
type: Concept
broader: Catadioptric telescopes

Very small grains
type: Concept
broader: Interstellar dust

Vilnius photometry
type: Concept
broader: Medium band photometry
alternative label: Vilnius photometric system
modified: 2020-10-21T18:28:52.080Z
contributor: AAS Frey.Katie

Virgo Cluster
type: Concept
broader: Galaxy clusters
related: Virgo Supercluster
contributor: AAS Frey.Katie
definition: The largest and nearest galaxy cluster to the Local Group. The Virgo cluster spans 120 square degrees on the sky and contains on the order of 2,000 galaxies. It is located at a distance of about 60 million light-years. It is an irregular cluster with no central concentration. The giant elliptical galaxy M87 is the most massive in the cluster.
modified: 2020-11-19T16:56:25.702Z
editorial note: Definition Provenance
  created: 2020-11-19T16:56:35.269Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-19T16:56:35.299Z

Virgo Supercluster
type: Concept
alternative label: Local Supercluster
alternative label: Virgo SC
broader: Superclusters
related: Virgo Cluster
contributor: AAS Frey.Katie
definition: The irregular supercluster that contains the Virgo cluster and the Local Group. At least 100 galaxy groups and clusters are located within its diameter of 110 million light-years. It is one of millions of superclusters in the observable Universe.
modified: 2020-11-19T16:57:02.092Z
editorial note: Definition Provenance
  created: 2020-11-19T16:57:11.543Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:57:11.571Z

Visibility function
type: Concept
broader: Interferometry
contributor: AAS Frey.Katie
definition: The Fourier transform of a source's brightness distribution, weighted by the characteristics of the interferometer's antennas.
modified: 2020-11-19T16:57:40.789Z
modified: 2020-11-19T16:57:50.551Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T16:57:50.517Z

Optical astronomy
type: Concept
alternative label: Visible astronomical observations
alternative label: Visible telescopes
broader: Astronomical methods
related: Visible sources
alternative label: Visible astronomy
narrower: Optical identification
definition: An area of astronomy where astronomers observe and analyse light from the Universe that falls within the wavelength range that the human eye is sensitive to, about 400 nm (violet) to 750 nm (red), which is also referred to as visible light.
contributor: AAS Frey.Katie
modified: 2024-06-20T12:26:26.880Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-09T22:18:03.463Z
  comment: Wikipedia
editorial note: Definition Provenance
  created: 2024-06-20T12:27:02.849Z
  creator: AAS Frey.Katie
  comment: Combined and modified from ESA and An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malay
modified: 2024-06-20T12:27:02.855Z

Visual binary stars
type: Concept
alternative label: Visual binaries
broader: Binary stars

Voids
type: Concept
broader: Large-scale structure of the universe
broader: Cosmic web
broader: Galaxy physics
broader: Intergalactic medium
alternative label: Galaxy voids
alternative label: Intergalactic voids
definition: A large region of cosmic space without galaxies. The first of these voids to be discovered lies in the direction of Bootes and is some 300 million light-years across. It is estimated that voids take up about 98% of the volume of the Universe, with clusters of galaxies concentrated in the thin walls that surround them.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:47:30.471Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:26:40.777Z
modified: 2020-11-04T21:26:40.817Z

Volcanoes
type: Concept
broader: Planetary structure
definition: An opening in the Earth's crust from which lava, ash, and hot gases flow or are ejected during an eruption.
contributor: AAS Frey.Katie Admin
alternative label: Volcano
related: Tectonics
modified: 2020-11-12T19:47:19.950Z
modified: 2020-11-04T21:25:54.582Z
editorial note: Definition Provenance
  created: 2020-11-04T21:25:54.551Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

von Zeipel theorem
type: Concept
alternative label: von Zeipel's theorem
broader: Analytical mathematics
related: Stellar rotation
contributor: AAS Frey.Katie Admin
definition: A theorem that establishes a relation between the radiative flux at some colatitude on the surface of a rotating star and the local effective gravity (which is a function of the angular velocity and colatitude). For a rotating star in which centrifugal forces are not negligible, the equipotentials where gravity, centrifugal force, and pressure are balanced will no longer be spheres. The theorem states that the radiative flux is proportional to the local effective gravity at the considered colatitude, F(θ) ∝ g_eff (θ)α, where α is the gravity darkening coefficient. As a consequence, the stellar surface will not be uniformly bright, because there is a much larger flux and a higher effective temperature at the pole than at the equator (T_eff (θ) ∝ g_eff (θ)β, where β is the gravity darkening exponent. In massive stars this latitudinal dependence of the temperature leads to asymmetric mass loss and also to enhanced average mass loss rates.
modified: 2020-11-24T17:31:52.824Z
editorial note: Definition Provenance
  created: 2020-11-19T16:59:12.800Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-19T16:59:12.832Z
contributor: AAS Frey.Katie

VY Sculptoris stars
contributor: AAS Frey.Katie
type: Concept
broader: Nova-like variable stars
alternative label: VY Sculpturis stars
modified: 2024-06-20T12:31:47.203Z

W Virginis variable stars
type: Concept
alternative label: W Virginis stars
alternative label: W Virginis variables
alternative label: W-Virginis variables
broader: Type II Cepheid variable stars
definition: A member of a class of pulsating stars with a period of 1 to 35 days located in the instability strip of the H-R diagram. Also known as type II Cepheid variables, W Virginis stars are typically 1.5 mag fainter than classical Type I Cepheids and have a mass less than that of the Sun. They also exhibit a period-luminosity relation which is distinct, but works in a similar way to the relation for Type I Cepheids. Hence W Virginis stars can also be used to measure Galactic and extragalactic distances.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:23:47.116Z
modified: 2020-11-04T21:24:01.861Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:24:01.833Z

Walraven photometry
type: Concept
alternative label: V b l uw photometry
broader: Medium band photometry
alternative label: Walraven photometric system
definition: A photometric system with five wavelength ranges that does not use filters. Instead it uses prisms and lenses (spectroscopy) to select the bands simultaneously. The wavelengths and the bandwidths are: W, 3250 and 140 Å; U, 3630 and 240 Å; L, 3840 and 230 Å; B, 4320 and 450 Å; and V, 5470 and 720 Å. The Walraven photometer was unique in design and remained literally unique as copies were never built. In addition, during its whole life the photometer was mounted permanently on the same telescope that had been built specifically for this instrument, the 91 cm 'Lightcollector' reflector, which started in 1958 at the Leiden Southern Station in Broederstroom, South-Africa. After 20 years in South-Africa the telescope and photometer were moved to the European Southern Observatory La Silla observatory in Chile. The photometric observations were resumed in March 1979 and continued for another 12 years until the decommissioning of the photometer in 1991.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:34:25.130Z
editorial note: Definition Provenance
  created: 2020-11-19T17:00:44.942Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie
modified: 2020-11-19T17:00:44.971Z

Warm-hot intergalactic medium
type: Concept
alternative label: WHIM
alternative label: Warm hot intergalactic medium
alternative label: Warm-hot intergalactic matter
broader: High energy astrophysics
broader: Intergalactic medium phases
broader: Large-scale structure of the universe
modified: 2020-11-19T17:01:13.278Z
contributor: AAS Frey.Katie
definition: The space containing a cluster of galaxies filled with a tenuous gas of temperature 105 to 107 K and density 10-6 to 10-4 cm-3. WHIM has been continuously shock-heated during the process of structure formation. It is so highly ionized that it can only absorb or emit far-ultraviolet and soft X-ray photons, primarily at spectral lines of highly ionized C, O, Ne, and Fe. WHIM is thought to be the main reservoir of missing baryons.
modified: 2020-11-19T17:01:22.895Z
editorial note: Definition Provenance
  created: 2020-11-19T17:01:22.859Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Warm dark matter
type: Concept
alternative label: WDM
broader: Dark matter

Warm ionized medium
type: Concept
alternative label: DIG
alternative label: Defuse ionized gas
alternative label: Reynolds' layer
alternative label: WIM
broader: Interstellar phases
modified: 2021-09-27T15:44:11.279Z
preferred label: Warm ionised medium
contributor: AAS Frey.Katie Admin

Warm neutral medium
type: Concept
alternative label: WNM
broader: Interstellar phases

Brane cosmology
type: Concept
broader: Cosmology

Water masers
type: Concept
alternative label: H2O masers
broader: Astrophysical masers
definition: An interstellar maser phenomenon in which water (H_{2}O) molecules undergo the processes of population inversion and stimulated emission. H_{2}O masers are detected toward star formation regions and the envelopes of evolved stars. The maser emission comes from regions that are typically quite small, not larger than the solar system. The main emission frequency is 22 GHz, which shows up in strong lines. There are, however, other H_{2}O maser transitions at 380 GHz and 183 GHz, which are much weaker than the 22 GHz line. The former transitions are sporadically detected since they are strongly absorbed in the Earth's atmosphere, because of its high water vapor content.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:20:02.516Z
modified: 2020-11-04T21:20:14.559Z
editorial note: Definition Provenance
  created: 2020-11-04T21:20:14.529Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Water vapor
type: Concept
alternative label: Aqueous vapor
alternative label: Aqueous vapour
preferred label: Water vapour
broader: Planetary atmospheres
broader: Greenhouse gases
modified: 2021-09-27T15:44:50.307Z
contributor: AAS Frey.Katie Admin
definition: Water in the gaseous state. Atmospheric water in vapor form; one of the most important components of the atmosphere.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T17:02:26.689Z
contributor: AAS Frey.Katie
modified: 2020-11-19T17:02:26.722Z

Waveband photometry
type: Concept
broader: Photometry
narrower: Ultraviolet photometry
narrower: X-ray photometry
narrower: Infrared photometry

WC stars
type: Concept
broader: Wolf-Rayet stars
alternative label: WC-type stars
definition: A Wolf-Rayet star whose spectrum is dominated by emission lines of ionized carbon: C III 5696 Å, C III / C IV 4650 Å, C IV 5801-12 Å. This type is divided in sub-types WC4 to WC9.
modified: 2020-11-04T21:08:47.082Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-04T21:09:02.394Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T21:09:02.424Z

Weak-line T Tauri stars
type: Concept
alternative label: WTTS
broader: T Tauri stars
alternative label: Weak-emission T Tauri stars
alternative label: Weak Emission T Tauri stars
definition: A T Tauri star that lacks strong emission lines in its optical spectrum, and lacks both strong stellar wind and infrared excess. These objects are believed to be pre-main sequence stars without obvious signs for disk accretion. Weak-line T Tauri stars result from the evolution of classical T Tauri stars.
modified: 2020-11-04T19:47:48.745Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T19:47:58.983Z
modified: 2020-11-04T19:47:59.018Z

Weak G band stars
type: Concept
broader: Giant stars

Weak gravitational lensing
type: Concept
broader: Gravitational lensing
contributor: AAS Frey.Katie
definition: A gravitational bending of light by structures in the Universe that distorts the images of distant galaxies. The distortion allows the distribution of dark matter and its evolution with time to be measured, thereby probing the influence of dark energy on the growth of structures. Weak gravitational lensing is generally difficult to identify in individual images, in contrast to strong gravitational lensing.
modified: 2020-11-19T17:03:39.701Z
modified: 2020-11-19T17:03:50.815Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T17:03:50.780Z

White dwarf stars
broader: Stellar evolutionary types
type: Concept
alternative label: White dwarfs
narrower: DC stars
narrower: ZZ Ceti stars
narrower: DZ stars
narrower: DQ stars
narrower: DA stars
narrower: DB stars
narrower: DO stars
related: Supernovae
related: Type Ia supernovae
related: Chandrasekhar limit
broader: Compact objects
contributor: AAS Frey.Katie Admin
alternative label: Degenerate dwarf stars
alternative label: Degenerate dwarf
definition: A compact star of high surface temperature, low luminosity, and high density (10^5 - 10^8 g cm^-3), with roughly the mass of the Sun (mean mass ~ 0.6 M_sun) and the radius of the Earth (R ~ 0.01 R_sun), representing the end-point of the evolution of all stars with masses less then ~ 5-9 solar masses. A white dwarf is what remains after the central star of a planetary nebula fades and becomes cool. The Chandrasekhar limit of 1.43 solar masses is the highest mass that a white dwarf can achieve before electron degeneracy pressure is unable to support it. In the Hertzsprung-Russell diagram, white dwarfs form a well-defined sequence around 8 magnitudes fainter than the main sequence. They are composed of a core of carbon and oxygen nuclei and degenerate electrons surrounded by a thin shell of helium and an outer skin of hydrogen. White dwarf's radiation is the leftover heat from the star's past when its core was an active nuclear reactor. The star slowly cools as heat escapes through the non-degenerate envelope. The first white dwarf to be discovered was Sirius B, the companion of Sirius. White dwarfs are divided into several types, according to their spectral features, which depend on the type of shell burning that dominated as it became a planetary nebula: DA white dwarf; DB white dwarf; DC white dwarf; DO white dwarf; DZ white dwarf; DQ white dwarf.
modified: 2020-11-04T21:11:39.147Z
modified: 2020-11-04T21:11:51.581Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:11:51.552Z

Chandrasekhar limit
related: White dwarf stars
type: Concept
broader: Gravitational collapse
scope note: Not to be confused with the Schonberg-Chandrasekhar limit.
related: Type II supernovae
definition: A limiting mass of about 1.44 Solar masses that the theory predicts a non-rotating white dwarf can attain without collapsing to become a neutron star or a black hole. Over this critical mass, the degeneracy pressure will be unable to bear the load of the bulk mass.
contributor: AAS Frey.Katie Admin
modified: 2021-03-30T14:12:17.972Z
modified: 2020-11-03T19:10:03.342Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:10:03.310Z
  creator: AAS Frey.Katie

Active sun
type: Concept
broader: Solar cycle
contributor: AAS Frey.Katie
related: Quiet sun
definition: The Sun during its 11-year cycle of activity when spots, flares, prominences, and variations in radiofrequency radiation are at a maximum.
modified: 2020-11-02T15:26:33.351Z
editorial note: Definition Provenance
  created: 2020-11-02T15:27:06.321Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-02T15:27:06.351Z

Bright nebulae
type: Concept
alternative label: Bright nebula
broader: Nebulae
definition: In contrast to a dark nebula, a bright cloud of interstellar gas and dust. The term designates both emission nebulae and reflection nebulae.
modified: 2020-11-02T16:28:38.476Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:28:50.363Z
modified: 2020-11-02T16:28:50.398Z

Wide-field telescopes
type: Concept
alternative label: Wide field telescopes
broader: Telescopes
narrower: Baker-Nunn cameras
narrower: All-sky cameras

Wide binary stars
type: Concept
broader: Binary stars
definition: A binary system with semi-major axis as large as 10,000 astronomical units.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:09:47.096Z
modified: 2020-11-04T21:09:57.836Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:09:57.807Z

Wilson effect
type: Concept
broader: Sunspots
contributor: AAS Frey.Katie
definition: A phenomenon in which the shape of sunspots flattens as they approach the Sun's limb due to the solar rotation. More specifically, when a sunspot approaches the solar limbs the width of the penumbra, relative to the umbra, on the side facing the center of the Sun seems to become narrower than on the side facing the limb. This phenomenon arises from a projection effect, and is due to a geometrical depression (the Wilson depression) in the layers of constant optical depth in sunspots.
modified: 2020-11-19T17:05:24.953Z
modified: 2020-11-19T17:05:35.122Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T17:05:35.088Z

Winter solstice
type: Concept
broader: Solstice
contributor: AAS Frey.Katie
definition: The moment in the northern hemisphere when the Sun attains its lowest declination of -23°26' (or -23°.44) with respect the equator plane. It happens when the Earth's axis is orientated directly away from the Sun, on 21 or 22 December. During the northern winter solstice the Sun appears to be directly overhead at noon for places situated at latitude 23.44 degrees south, known as the tropic of Capricorn. The winter solstice can occur at any moment during the day. Two successive winter solstices are shifted in time by about 6 h. The winter solstice in the northern hemisphere is the summer solstice in the southern hemisphere.
modified: 2020-11-19T17:06:06.191Z
modified: 2020-11-19T17:06:16.609Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-19T17:06:16.577Z

WN stars
type: Concept
broader: Wolf-Rayet stars
alternative label: WN-type stars
definition: A Wolf-Rayet star whose spectrum is dominated by emission lines of ionized nitrogen: N II 3995 Å, N III 4634-4661 Å, N III 5314 Å, N IV 3479-3484 Å, N IV 4058 Å, N V 4603 Å, N V 4619 Å, and N V 4933-4944 Å. This type is divided in sub-types WN2 to WN11.
modified: 2020-11-04T21:07:55.107Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:08:13.957Z
editorial note: Definition Provenance
  created: 2020-11-04T21:08:13.926Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Wolf-Rayet stars
type: Concept
alternative label: WR stars
alternative label: Wolf Rayet stars
broader: Early-type emission stars
narrower: WC stars
narrower: WCN stars
narrower: WN stars
related: Stellar classification
definition: A type of very luminous, very hot (as high as 50,000 K) stars whose spectrum is characterized by broad emission lines (mainly He I and He II), which are presumed to originate from material ejected from the star at very high (~ 2000 km s^-1) velocities. The most massive O stars (M > 25 solar masses for solar metallicity) become W-R stars around 2 and 3 million years after their birth, spending only some few hundreds of thousands of years (≤ 10^6 years) in this phase until they explode as type Ib and type Ic supernovae. The minimum stellar mass that an O star needs to reach the W-R phase and its duration is dependent on metallicity.
modified: 2020-11-04T21:07:25.897Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:44:29.445Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-24T16:44:29.409Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Wolf diagram
type: Concept
broader: Astrometry

Wormholes
type: Concept
alternative label: Einstein-Rosen Bridge
broader: Gravitational singularities
related: Kerr black holes
definition: A hypothetical topological feature, based on general relativity, that connects two different points like a 'tunnel' in space-time. The most common concept of a wormhole is an Einstein-Rosen bridge. A trip through the wormhole could take much less time than a journey between the same starting and ending points in normal space. Wormholes have various types, intra-universe wormholes (connecting two distant regions of our Universe with each other) and inter-universe wormholes (that connect our Universe with another universe).
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:06:10.120Z
editorial note: Definition Provenance
  created: 2020-11-04T21:06:24.923Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T21:06:24.954Z

WZ Sagittae stars
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: WZ Sge stars
broader: Dwarf novae
broader: Cataclysmic variable stars
definition: A subclass of dwarf novae with an extremely long outburst period, comparable with that of a recurrent nova.
modified: 2020-11-04T21:05:08.766Z
modified: 2020-11-04T21:05:21.118Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:05:21.090Z
  creator: AAS Frey.Katie Admin

Cataclysmic variable stars
narrower: WZ Sagittae stars
type: Concept
alternative label: Cataclysmic binaries
alternative label: Cataclysmic binary stars
alternative label: Cataclysmic variables
broader: Intrinsic variable stars
narrower: Nova-like variable stars
narrower: Novae
narrower: SX Arietis variable stars
narrower: UV Persei stars
narrower: AM Herculis stars
broader: Semi-detached binary stars
contributor: AAS Frey.Katie Admin
narrower: AM Canum Venaticorum stars
definition: A variable star that shows a sudden and dramatic change in brightness, including flare stars, novae, and some types of symbiotic stars. They are believed to be very close binary systems consisting of an accreting white dwarf primary and an evolved late-type secondary star that has filled its Roche lobe. For systems with an accretion disk, it is believed that a thermal instability is the cause of repetitive outbursts observed in cataclysmic variables called dwarf novae.
modified: 2020-11-04T22:17:50.694Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T22:18:05.098Z
modified: 2020-11-04T22:18:05.132Z

Brightest cluster galaxies
type: Concept
broader: Giant galaxies

X-ray astronomy
type: Concept
alternative label: X-ray galaxies
broader: Astronomical methods
narrower: X-ray bright point
narrower: X-ray identification
related: X-ray sources
contributor: AAS Frey.Katie
definition: The study of celestial bodies using their X-ray emission. X-ray astronomy deals mainly with Galactic and extragalactic phenomena involving very high-energy photon emissions, covering a band of energies between 0.1 keV and 500 keV. The research field includes: X-ray binaries, cataclysmic variables, pulsars, black holes, dark matter, active galaxies, galactic clusters X-ray transients. The Earth's atmosphere absorbs most X-rays coming from outer space. X-ray astronomy therefore requires observations to be done above atmosphere.
modified: 2024-06-20T13:12:03.020Z
modified: 2020-11-19T17:08:23.203Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-19T17:08:23.172Z

X-ray binary stars
type: Concept
alternative label: X-ray binaries
broader: Compact binary stars
narrower: X-ray bursters
narrower: High mass x-ray binary stars
narrower: Low-mass x-ray binary stars
related: X-ray sources
broader: Semi-detached binary stars
definition: A binary star system where one of the stars has evolved and collapsed into an extremely dense body such as a white dwarf, a neutron star, or a black hole. The enormous gravitational attraction of the massive, dense, but dim component pulls material from the brighter, less massive star in an accretion disk. The gravitational potential energy of the accreted matter is converted to heat by viscosity and eventually to high-energy photons in the X-ray range. The brightest X-ray binary is Scorpius X-1.
modified: 2020-11-04T21:00:04.593Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:00:30.363Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:00:30.333Z

X-ray bright point
type: Concept
broader: X-ray astronomy

X-ray bursts
type: Concept
broader: Burst astrophysics
broader: X-ray sources
related: X-ray bursters
related: X-ray transient sources
definition: A rapid and intense surge of X-ray emission from some sources. They often last less than one second followed by an exponential decrease of typically a few seconds to a minute. Most X-ray bursts are believed to arise in X-ray binary systems due to nuclear fusion of material accreted onto a compact companion.
modified: 2020-11-04T21:00:55.123Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:01:09.788Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T21:01:09.823Z

X-ray detectors
type: Concept
broader: Astronomical detectors

X-ray identification
type: Concept
broader: X-ray astronomy

X-ray novae
type: Concept
broader: Novae

X-ray observatories
type: Concept
broader: Observatories

Brightness temperature
type: Concept
broader: Radio astronomy
broader: Astrometry
contributor: AAS Frey.Katie
definition: In radio astronomy, the temperature of a source calculated on the assumption that it is a blackbody emitting radiation of the observed intensity at a given wavelength.
modified: 2020-11-03T18:54:12.656Z
editorial note: Definition Provenance
  created: 2020-11-03T18:54:24.072Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:54:24.102Z

X-ray photometry
type: Concept
broader: Waveband photometry
narrower: Hardness ratio

X-ray quasars
type: Concept
broader: Quasars

X-ray sources
type: Concept
broader: Astronomical radiation sources
narrower: X-ray point sources
narrower: Cool cores
narrower: Diffuse x-ray background
related: X-ray binary stars
related: Solar x-ray flares
narrower: X-ray transient sources
narrower: X-ray bursts
related: X-ray bursters
related: X-ray astronomy
narrower: Ultraluminous x-ray sources
definition: An astronomical object whose dominant mechanism of radiation is through X-ray emission. X-ray sources contain an extremely hot gas at temperatures from 10^6 to 10^8 K. They are generated by various physical processes involving high energies, such as accretion on to a compact object, shock waves from supernovae, stellar winds, hot gas in stellar coronae, or hot spaces between galaxies in a cluster. The first celestial X-ray source, after the Sun, to be detected was Scorpius X-1 by means of rocket flight.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:02:02.977Z
modified: 2020-11-04T21:02:20.228Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:02:20.201Z

X-ray stars
type: Concept
broader: Emission line stars
narrower: Single x-ray stars

X-ray surveys
type: Concept
broader: Surveys

X-ray telescopes
type: Concept
broader: Space telescopes
definition: A telescope designed to focus X-rays from astronomical objects. X-ray telescopes function from orbital satellites because X-rays are absorbed by the Earth's atmosphere. These telescopes require special techniques since the conventional methods used in optical and radio telescopes are not adequate.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:04:02.473Z
modified: 2020-11-04T21:04:16.420Z
editorial note: Definition Provenance
  created: 2020-11-04T21:04:16.388Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Xenobiology
type: Concept
broader: Astrobiology
definition: The study of synthesizing and manipulating biological devices and systems.
contributor: AAS Frey.Katie
modified: 2020-11-19T17:11:22.812Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-19T17:11:32.409Z
  comment: Wikipedia
modified: 2020-11-19T17:11:32.435Z

Yellow hypergiant stars
type: Concept
alternative label: Rho Cassiopeiae
alternative label: Rho cas stars
broader: Hypergiant stars
definition: An evolved, very massive star of spectral type F or G with a very high luminosity (~10^5 times solar) lying near the empirical upper luminosity boundary in the H-R diagram (Humphreys-Davidson limit). Yellow hypergiants have high mass loss rates (10^-5 - 10^-3 solar masses per year) and are in a short, transitional evolutionary stage. Their evolutionary state is thought to correspond to post-red supergiants rapidly evolving in blueward loops in the H-R diagram. In their post-RSG blueward evolution these stars enter a temperature range (6000-9000 K), called yellow void, with increased dynamical instability. Their link to other advanced evolutionary phases of massive stars such as Luminous Blue Variables and Wolf-Rayet stars is still an open issue in stellar evolution theory. The most famous yellow hypergiant is Rho Cassiopeiae.
modified: 2020-11-04T20:56:37.894Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T20:56:59.421Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T20:56:59.388Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Broad-absorption line quasar
type: Concept
alternative label: BALQSO
broader: Quasars

Young star clusters
type: Concept
broader: Open star clusters

Young stellar objects
type: Concept
alternative label: YSO
broader: Protostars
related: Stellar evolution
narrower: T Tauri stars
contributor: AAS Frey.Katie Admin
narrower: FU Orionis stars
narrower: Herbig-Haro objects
related: Pre-main sequence stars
narrower: Herbig Ae/Be stars
alternative label: YSOs
definition: Any star that has evolved past the protostar stage, but has not yet arrived on the main sequence. There is a variety of YSOs depending on their age, mass, and environment, including Herbig stars, T Tauri stars, and, in general, compact infrared sources embedded in molecular clouds.
modified: 2020-11-04T20:54:16.271Z
modified: 2020-11-04T20:54:30.840Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T20:54:30.813Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Z Andromedae stars
type: Concept
broader: Symbiotic binary stars
broader: Close binary stars
broader: Emission line stars

Z Camelopardalis stars
type: Concept
broader: Dwarf novae

Zenith
type: Concept
broader: Horizontal coordinate system
contributor: AAS Frey.Katie
modified: 2020-11-19T17:12:57.134Z
definition: The point on the celestial sphere directly above the observer's head, opposite to the direction in which gravity acts. Opposite of nadir.
modified: 2020-11-19T17:13:09.922Z
editorial note: Definition Provenance
  created: 2020-11-19T17:13:09.897Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Zenith hourly rate
type: Concept
alternative label: ZHR
alternative label: Zenith hour rate
contributor: AAS Frey.Katie Admin
definition: The number of meteors expected to be seen under ideal conditions if the radiant of the meteoroid stream is at the zenith of the observer.
broader: Meteor showers
modified: 2020-11-09T22:12:32.052Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T20:53:03.516Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T20:53:03.542Z

Broad band photometry
type: Concept
alternative label: Broadband photometry
alternative label: Wide-band photometry
broader: Photometric systems
narrower: RGB photometry
narrower: RGU photometry
narrower: Sloan photometry
narrower: Bessel photometry
narrower: BV photometry
narrower: Cape photometry
narrower: Cape RI photometry
narrower: Gunn photometry
narrower: HST photometry
narrower: Johnson photometry
narrower: Kron-Cousins photometry
related: Infrared photometry
narrower: AB photometry
narrower: Vega photometry

Zenith telescopes
type: Concept
alternative label: Zenith sectors
broader: Transit instruments
modified: 2020-11-04T20:51:54.981Z
definition: A telescope that is mounted on a vertical axis or moves only a small amount from the vertical. It is primarily used to determine positional measurement of stars moving near the zenith. The advantage is that there is no atmospheric refraction occurring at the zenith. If a star on one night passes through the center of eyepiece, one must observe it six month later, and see if the star has been offset by the center. A shift would mean a measure of parallax.
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T20:52:09.420Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T20:52:09.462Z

Zenith tubes
type: Concept
alternative label: PZT
alternative label: Photographic zenith tube
alternative label: Zenithal tubes
broader: Transit instruments
broader: Early astronomical instruments

Zero-age horizontal branch stars
type: Concept
alternative label: ZAHB
alternative label: ZAHB stars
broader: Horizontal branch stars
alternative label: Zero age horizontal branch stars
related: Horizontal branch
related: Hertzsprung Russell diagram
definition: A star that has arrived on the horizontal branch after leaving the red giant branch. It begins helium burning in its core.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T20:49:02.035Z
modified: 2020-11-24T16:43:50.666Z
editorial note: Definition Provenance
  created: 2020-11-24T16:43:50.635Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Zirconium stars
type: Concept
broader: S stars
broader: Chemically peculiar stars

Zodiacal cloud
type: Concept
alternative label: Zodiacal dust
alternative label: Zodiacal dust cloud
alternative label: Zodiacal light
broader: Interplanetary dust
related: Exozodiacal dust
narrower: Zodiacal dust bands

Zone of totality
type: Concept
broader: Eclipses

ZZ Ceti stars
type: Concept
broader: Multi-periodic variable stars
broader: White dwarf stars
definition: A member of a class of non-radially pulsating stars that change their brightnesses with periods from 30 seconds to 25 minutes and amplitudes from 0.001 to 0.2 mag in V. Their location on the Hertzsprung-Russell diagram identifies them as white dwarf stars that have entered the instability strip as they evolve along the white dwarf track.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T20:47:50.198Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T20:48:02.844Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T20:48:02.882Z

Burkert profile
type: Concept
broader: Astronomical models

Burst astrophysics
type: Concept
broader: Stellar phenomena
broader: High energy astrophysics
narrower: Optical bursts
narrower: Radio bursts
narrower: Rapid bursts
narrower: X-ray bursts
narrower: Gamma-ray bursts
related: Supernovae

BV photometry
type: Concept
broader: Broad band photometry

BW stars
type: Concept
broader: B stars
contributor: AAS Frey.Katie
alternative label: BW-type stars
broader: Helium-weak stars
modified: 2020-09-09T19:01:45.035Z

Adaptive interferometry
type: Concept
broader: Interferometry

Calendars
type: Concept
broader: Astronomical reference materials
definition: Any of various systems for measuring and recording the passage of time by dividing the year into days, weeks, and months. A table showing the months, weeks, and days in at least one specific year.
modified: 2020-11-04T22:10:14.371Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T22:10:27.544Z
modified: 2020-11-04T22:10:27.578Z

Cape photometry
type: Concept
alternative label: UCBVc BV photometry
broader: Broad band photometry

Cape RI photometry
type: Concept
broader: Broad band photometry

Carbon-nitrogen cycle
type: Concept
alternative label: CNO cycle
alternative label: Carbon cycle
alternative label: Carbon cycling
alternative label: Carbon nitrogen cycle
broader: Hydrogen burning

Carbon burning
type: Concept
broader: Nucleosynthesis
contributor: AAS Frey.Katie Admin
definition: The stage in the evolution of a star after helium burning when the core of the star consists mainly of carbon and oxygen. In stars of mass greater than about 8 solar masses, whose cores reach a temperature above 5 x 10^8 K and density above 3 x 10^9 kg m^-3, carbon burning can begin via reactions such as the following: 12C + 12C → 20Ne + 4He or 12C + 12C → 23Na + p or 12C + 12C → 23Mg + n. The time-scale for this phase of nucleosynthesis is of order of five hundred years.
modified: 2020-11-24T19:33:11.112Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-24T17:08:46.674Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-24T17:08:46.702Z

Carbon dioxide
type: Concept
alternative label: CO2
alternative label: CO_2
broader: Greenhouse gases
contributor: AAS Frey.Katie
definition: CO_2, also called carbonic acid gas. A colorless gas which occurs in the atmosphere playing an essential part in animal respiration and the growth of green plants. It is formed by the oxidation of carbon and carbon compounds. Carbon dioxide is the most important greenhouse gas produced by human activities, primarily through the combustion of fossil fuels. Its concentration in the Earth's atmosphere has risen by more than 30% since the Industrial Revolution. CO_2 forms a solid at -78.5 °C at atmospheric pressure, and is used as a refrigerant in this form as a dry ice for the preservation of frozen foods. As carbon dioxide gas is heavier than air and does not support combustion, it is used in fire extinguishers. CO_2 is present in the interstellar medium and is one of the main molecules in comets.
modified: 2020-11-03T18:56:45.647Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:56:57.918Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:56:57.941Z

Carbon planets
type: Concept
broader: Exoplanets

Carbon stars
type: Concept
broader: Chemically peculiar stars
narrower: N stars
narrower: R stars
related: Late-type giant stars
definition: A class of red giant stars whose spectra show strong molecular bands of carbon compounds.
contributor: AAS Frey.Katie
modified: 2020-10-26T19:30:31.941Z
modified: 2020-10-26T19:30:43.126Z
editorial note: Definition Provenance
  created: 2020-10-26T19:30:43.100Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

53 Persei stars
type: Concept
broader: B stars
broader: Pulsating variable stars

Carbonaceous chondrites
type: Concept
broader: Chondrites
definition: A rare type of stony meteorite having a higher carbon content than other classes of meteorite. They represent only ~5% of the known meteorites. Their bulk composition is mainly silicates, oxides and sulfides, whilst the minerals olivine and serpentine are characteristic. The six classes of carbonaceous chondrites are: CI chondrites, CM chondrites, CV chondrites, CO chondrites, CK chondrites, CR chondrites, CH chondrites, and CB chondrites.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T22:18:58.675Z
modified: 2020-11-04T22:19:11.656Z
editorial note: Definition Provenance
  created: 2020-11-04T22:19:11.625Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Carbonaceous grains
type: Concept
broader: Interstellar dust

Cassegrain telescopes
type: Concept
broader: Reflecting telescopes
narrower: Ritchey-Chrétien telescopes
definition: A reflecting telescope whose primary mirror has a hole bored through the center to allow the reflected light from the convex secondary mirror be focused beyond the back end of the tube.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:35:20.832Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:35:32.758Z
modified: 2020-11-03T21:35:32.785Z

Catadioptric telescopes
type: Concept
broader: Optical telescopes
narrower: Maksutov telescopes
narrower: Baker-Nunn cameras
narrower: Schmidt-Cassegrain telescopes
narrower: Schmidt cameras
narrower: Bouwers telescope

Catalogs
type: Concept
preferred label: Catalogues
broader: Astronomical reference materials
narrower: Radio source catalogs
narrower: Sky surveys
narrower: Celestial objects catalogs
narrower: FK catalog
narrower: Henry Draper catalog
narrower: Astrographic catalogs
definition: A list or record of items systematically arranged with descriptive details.
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:43:14.333Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-10-26T19:32:32.588Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-26T19:32:32.614Z

Caustic crossing
type: Concept
alternative label: Caustic-crossing
broader: Caustic curve
contributor: AAS Frey.Katie
modified: 2019-12-13T14:53:11.074Z

CCD observation
type: Concept
broader: Astronomical techniques

CCD photometry
type: Concept
alternative label: Charge-coupled device photometry
broader: Photometry

cD galaxies
type: Concept
alternative label: Type-cD galaxies
alternative label: cD-type galaxies
broader: D galaxies
broader: Giant galaxies

Aerolites
type: Concept
broader: Meteorites
contributor: AAS Frey.Katie
definition: A stony meteorite consisting of silicate minerals. This alternative name for a stony meteorite, is now largely obsolete.
modified: 2020-11-03T17:51:12.382Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T17:51:26.751Z
modified: 2020-11-03T17:51:26.780Z

Celestial equator
type: Concept
broader: Equatorial coordinate system
contributor: AAS Frey.Katie
definition: An imaginary great circle on the sky half-way between the celestial poles. It is the projection of the equator of the Earth on the sky.
modified: 2020-11-03T18:59:11.170Z
modified: 2020-11-03T18:59:22.274Z
editorial note: Definition Provenance
  created: 2020-11-03T18:59:22.241Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Celestial mechanics
type: Concept
broader: Gravitation
narrower: N-body problem
narrower: Orbits
narrower: Perturbation methods
narrower: Three-body problem
narrower: Two-body problem
narrower: Close encounters
narrower: Apparent superluminal motion
narrower: Astrodynamics
narrower: Lunar theory
contributor: AAS Frey.Katie
definition: The branch of astronomy that deals with the calculation of motions of celestial bodies under the action of their mutual gravitational attractions.
modified: 2020-11-03T19:00:34.397Z
narrower: Kepler's laws
editorial note: Definition Provenance
  created: 2020-11-03T19:00:45.998Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T19:00:46.028Z

Celestial objects catalogs
type: Concept
broader: Catalogs
preferred label: Celestial objects catalogues
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:43:49.515Z

Celestial poles
type: Concept
broader: Equatorial coordinate system
narrower: North celestial pole
narrower: South celestial pole
definition: The point of the sky, north or south, where the projection of the Earth's axis of rotation intersects the celestial sphere. They are at 90° relative to the celestial equator. Because of precession, the celestial poles describe a circle around the ecliptic's poles every 25,800 years.
contributor: AAS Frey.Katie
modified: 2020-10-26T19:39:23.217Z
editorial note: Definition Provenance
  created: 2020-10-26T19:39:43.928Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-26T19:39:43.955Z

Celestial sphere
type: Concept
broader: Equatorial coordinate system
narrower: Constellations
contributor: AAS Frey.Katie
definition: An imaginary sphere, of large but indefinite dimension, used as a basis to define the position coordinates of celestial bodies. The center can be the Earth, the observer, or any other point which plays the role of origin for a given system of coordinates. Seen from the Earth, the celestial sphere rotates around the celestial axis every 23h 56m 04s (the sidereal day), as a result of the Earth's rotation. Two important circles on the celestial sphere are the celestial equator and the ecliptic. The angle between them, about 23.40 degrees, is known as the obliquity of the ecliptic. The celestial equator and the ecliptic intersect at two points, vernal equinox and autumnal equinox. The positions of the celestial poles and therefore that of the celestial equator move gradually on the celestial sphere, due to precession.
modified: 2020-11-03T19:01:57.850Z
narrower: Asterisms
narrower: Star lore
modified: 2020-11-03T19:02:10.664Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:02:10.635Z
  creator: AAS Frey.Katie

Centaur group
type: Concept
scope note: Not to be confused with Centaurus meteor shower.
alternative label: Centaur asteroids
alternative label: Centaurs
definition: An asteroid whose orbit around the Sun lies typically between the orbits of Jupiter and Neptune (5 to 30 astronomical units). The first Centaur, called Chiron, was discovered in 1977, but since then more than 100 roughly similar objects have been found. Three centaurs, Chiron, 60558 Echeclus, and 166P/NEAT 2001 T4, have been found to display cometary comas. Chiron and 60558 Echeclus are now classified as both asteroids and comets. Most of the Centaur asteroids are probably dormant comets from the Kuiper belt which have been pulled in by the gravity of outer planets.
contributor: AAS Frey.Katie Admin
broader: Asteroids
modified: 2020-12-09T15:41:01.983Z
modified: 2020-10-26T19:36:58.140Z
editorial note: Definition Provenance
  created: 2020-10-26T19:36:58.114Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Center of mass
type: Concept
preferred label: Centre of mass
broader: Orbital elements
alternative label: Center of gravity
definition: A fixed point in a body through which the resultant force of gravitational attraction acts.
modified: 2021-08-24T15:25:06.254Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T19:05:13.699Z
editorial note: Definition Provenance
  created: 2020-11-03T19:05:13.668Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Cepheid distance
type: Concept
broader: Stellar distance

Cepheid variable stars
type: Concept
alternative label: Bump cepheid
alternative label: Cepheid stars
alternative label: Cepheid variables
alternative label: Cepheids
alternative label: Classical Cepheid
broader: Pulsating variable stars
narrower: Young disk Cepheid variable stars
narrower: Delta Cepheid variable stars
narrower: Double-mode Cepheid variable stars
narrower: Anomalous Cepheid variable stars
narrower: Type II Cepheid variable stars
definition: A class of luminous, yellow supergiants that are pulsating variables and whose period of variation is a function of their luminosity. These stars expand and contract at extremely regular periods, in the range 1-50 days. Their highest brightness and surface temperature occur when their expansion velocity is greatest. Similarly, their minima in brightness and temperature occur when they are in the contraction phase. The longer the period, the more luminous the star. The process that drives the pulsation of Cepheid variables is the kappa mechanism. In fact, Cepheids provide one of the most powerful tools for measuring distances to other galaxies (period-luminosity relation). However, this method is limited to the distance of the Virgo cluster of galaxies (15-20 Mpc) even with the HST or the largest ground-based telescopes. One particularly special Cepheid is the North Star, Polaris.
contributor: AAS Frey.Katie Admin
modified: 2022-06-24T15:29:40.997Z
editorial note: Definition Provenance
  created: 2020-10-26T19:38:31.623Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-26T19:38:31.650Z
contributor: AAS Frey.Katie

Ceres
type: Concept
broader: Dwarf planets
definition: Once qualified as the largest known asteroid, Ceres is now classified as a dwarf planet (2006 IAU General Assembly). It is approximately 950 km across, and resides with tens of thousands of asteroids in the main asteroid belt; it is the largest body of the belt. Its mass is 9.4 x 10^20 kg, its rotation period 9.074 hours, its orbital period 4.60 years, and its semi-major axis 2.767 AU. NASA's Dawn spacecraft, which was placed in orbit around Ceres in 2015, has mapped its surface in great detail. Dawn discovered very bright spots, which reflect far more light than their much darker surroundings. The most prominent of these spots lie inside the crater Occator and suggest that Ceres may be a much more active world than most of its asteroid neighbors.
contributor: AAS Frey.Katie Admin
alternative label: (1) Ceres
alternative label: Asteroid Ceres
alternative label: 1 Ceres
broader: Main belt asteroids
modified: 2022-06-21T18:30:40.244Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:07:30.011Z
  creator: AAS Frey.Katie
modified: 2020-11-03T19:07:30.038Z

Aeronomy
type: Concept
broader: Atmospheric science
contributor: AAS Frey.Katie
modified: 2020-11-03T17:41:20.275Z
definition: The study of the upper atmosphere, especially of regions of ionized gas.
modified: 2020-11-03T17:41:36.725Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T17:41:36.693Z

CH stars
type: Concept
broader: Giant stars

Charged black holes
type: Concept
broader: Classical black holes
narrower: Reissner-Nordström black holes
narrower: Kerr-Newman black holes

Chemical abundances
type: Concept
alternative label: Chemical abundance
alternative label: Element abundance
broader: Astrochemistry
narrower: Metallicity
narrower: Abundance ratios
narrower: Nuclear abundances
narrower: Overabundances
narrower: Stellar abundances
narrower: Underabundances
narrower: Cosmic abundances
narrower: Frozen in elements
narrower: Galaxy abundances
narrower: Interstellar abundances
narrower: Isotopic abundances
alternative label: Elemental abundances
narrower: Solar abundances
narrower: Galactic abundances
narrower: Intergalactic abundances
alternative label: Elemental composition
alternative label: Chemical composition
definition: The relative amount of a given chemical element or chemical compound with respect to another element or compound in a given sample.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:27:01.920Z
modified: 2020-11-03T19:11:00.863Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:11:00.832Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Chemical enrichment
type: Concept
broader: Galaxy chemical evolution
contributor: AAS Frey.Katie Admin
definition: The process by which the relative abundance of a given chemical element or species in an astrophysical object is increased. For example the increase of the heavy element content of the interstellar medium due to stellar evolution.
modified: 2020-11-24T17:26:16.093Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:12:26.057Z
contributor: AAS Frey.Katie
modified: 2020-11-03T19:12:26.085Z

Chemically peculiar stars
type: Concept
alternative label: CP stars
alternative label: Metal-rich stars
broader: Stellar types
narrower: Manganese stars
narrower: Mercury-manganese stars
narrower: Chemically peculiar giant stars
narrower: Peculiar variable stars
narrower: Strontium stars
narrower: Technetium stars
narrower: Bp stars
narrower: Zirconium stars
narrower: Shell stars
narrower: Carbon stars
narrower: Am stars
narrower: Ap stars
narrower: Heavy metal stars
narrower: Helium-rich stars
narrower: Helium-weak stars
narrower: Hydrogen deficient stars
narrower: Lithium stars
narrower: Magnetic stars
narrower: CEMP stars
contributor: AAS Frey.Katie
definition: Main sequence stars of spectral type A or B identified by the presence of anomalously strong or weak absorption lines of certain elements in their spectra. CP stars have been divided into four main classes on the basis of their spectra: 1) non-magnetic metallic-lined (CP1, Am star), magnetic (CP2, Ap star), non-magnetic mercury-manganese (CP3, HgMn star), and helium-weak (CP4, He-weak star).
modified: 2020-11-03T19:13:44.812Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:14:02.047Z
  creator: AAS Frey.Katie
modified: 2020-11-03T19:14:02.079Z

Chlorofluorocarbons
type: Concept
broader: Greenhouse gases

Chondrites
type: Concept
broader: Meteorites
narrower: Carbonaceous chondrites
narrower: Chondrules
definition: The most common type of meteorites containing chondrules. These stony meteorites make up about 86% of all meteorites. An important feature of the chondrites is that, with the exception of a few highly volatile elements, they have the same composition as the Sun.
modified: 2020-10-26T19:41:31.558Z
contributor: AAS Frey.Katie
modified: 2020-10-26T19:41:46.116Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T19:41:46.091Z

Chondrules
type: Concept
broader: Chondrites
definition: Millimeter-sized grains of silicate sometimes found in large numbers in chondrite meteorites. They are essentially glassy beads made by a violent but brief heating event that caused dust grains to form melt droplets. However, the cause of the heating remains unknown.
modified: 2020-10-26T19:42:51.910Z
contributor: AAS Frey.Katie
modified: 2020-10-26T19:43:02.903Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:43:02.876Z

Alfven waves
type: Concept
alternative label: Alfven surface waves
alternative label: Alfvén surface waves
alternative label: Alfvén waves
broader: Space plasmas
contributor: AAS Frey.Katie
broader: Solar chromosphere
related: Magnetohydrodynamics
modified: 2020-11-03T17:53:03.726Z
definition: A magnetohydrodynamic wave in a magnetized plasma, arising as a result of restoring forces associated with the magnetic field. It is a transverse wave which propagates in the direction of the magnetic field. Also called magnetohydrodynamic wave.
editorial note: Definition Provenance
  created: 2020-11-03T17:53:19.336Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T17:53:19.361Z

Chthonian planets
type: Concept
alternative label: Cthonian planets
broader: Exoplanets

CII region
type: Concept
broader: Astrochemistry

Circumstellar clouds
type: Concept
broader: Circumstellar matter

Circumstellar disks
type: Concept
alternative label: Circumstellar discs
broader: Circumstellar matter
narrower: Protoplanetary disks
narrower: Debris disks
definition: Any concentration of material in the form of a disk orbiting around a star.
contributor: AAS Frey.Katie
modified: 2020-10-26T19:48:08.473Z
modified: 2020-10-26T19:48:22.382Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T19:48:22.353Z

Circumstellar dust
type: Concept
broader: Circumstellar matter
contributor: AAS Frey.Katie
definition: Interstellar dust grains localized around various types of stars, such as asymptotic giant branch stars. Circumstellar dust occurs in the form of a spherical shell or a disk and is at the origin of an infrared excess for the central star.
modified: 2020-11-03T19:15:42.469Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:15:53.171Z
modified: 2020-11-03T19:15:53.206Z

Circumstellar envelopes
type: Concept
alternative label: Expanding circumstellar envelope
alternative label: Stellar envelope
broader: Circumstellar matter
definition: A very extensive envelope of cold gaseous materials surrounding evolved cool stars, notably red giants, red supergiants (Mira variables), or asymptotic giant branch stars. The typical size of such envelopes is several thousand times that of the stellar radius and their temperature ranges from 1000 to 10 K. Circumstellar envelopes result from mass loss from the central star (10-7 to 10-4 solar masses per year) and expand with moderate velocities (10 to 15 km sec^-1). The low temperature of the envelope is at the origin of the formation of molecules, which in certain conditions provide maser emission (H_{2}O, OH, SiO). Similarly, dust grains form in the envelope produce an infrared excess emission.
modified: 2020-12-17T16:52:12.444Z
contributor: AAS Frey.Katie Admin
modified: 2020-10-26T19:46:27.617Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T19:46:27.591Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie

Circumstellar gas
type: Concept
broader: Circumstellar matter

Circumstellar grains
type: Concept
broader: Circumstellar matter

Circumstellar masers
type: Concept
broader: Circumstellar matter
definition: Maser emission from molecules in the circumstellar envelopes of red giants, and also from regions around protostars.
modified: 2020-10-26T19:47:18.545Z
contributor: AAS Frey.Katie
modified: 2020-10-26T19:47:31.134Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T19:47:31.104Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Circumstellar matter
type: Concept
broader: Stellar astronomy
narrower: Circumstellar clouds
narrower: Circumstellar disks
narrower: Circumstellar dust
narrower: Circumstellar envelopes
narrower: Circumstellar gas
narrower: Circumstellar grains
narrower: Circumstellar masers
narrower: Circumstellar shells
contributor: AAS Frey.Katie
definition: Dust, gas and plasma around stars, generally present in the form of stellar winds or nebulae ejected by the stars.
modified: 2020-11-03T19:18:34.564Z
editorial note: Definition Provenance
  created: 2020-11-03T19:18:49.383Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:18:49.415Z

Circumstellar shells
contributor: AAS Frey.Katie
type: Concept
broader: Stellar structures
broader: Circumstellar matter
narrower: Rotating shells
narrower: Shell burning
narrower: Dust shells
definition: A shell of dust, molecules, and neutral gas around an evolved star resulting from an intensive mass loss phase, such as the asymptotic giant branch phase for low- and intermediate mass stars and LBVs or supernovae for massive stars.
modified: 2020-10-26T19:48:53.059Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:49:06.917Z
modified: 2020-10-26T19:49:06.945Z

Classical black holes
type: Concept
broader: Black holes
narrower: Nonrotating black holes
narrower: Rotating black holes
narrower: Uncharged black holes
narrower: Charged black holes

All-sky cameras
type: Concept
alternative label: All sky camera
broader: Wide-field telescopes
narrower: Cloud monitors

Classical Kuiper belt objects
type: Concept
alternative label: Classical Kuiper-belt objects
alternative label: Cubewanos
alternative label: cubewanos
broader: Trans-Neptunian objects
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:25:49.948Z
modified: 2020-12-16T20:21:11.177Z

Classical novae
type: Concept
alternative label: Classical nova
broader: Novae

Classical T Tauri stars
type: Concept
alternative label: C tt s
broader: T Tauri stars
definition: A T Tauri star in which accretion from a circumstellar disk is responsible for ultraviolet and infrared excess emission and for a moderate to strong emission line spectrum superimposed on the photospheric spectrum. Classical T Tauri stars probably evolve into weak-line T Tauri stars when their disks are fully accreted by the stars.
modified: 2020-10-26T19:53:42.225Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T19:53:55.363Z
modified: 2020-10-26T19:53:55.392Z

Classification systems
type: Concept
broader: Astronomical research
narrower: Stellar classification
narrower: Galaxy classification systems
narrower: Luminosity classification
definition: Systems for the grouping of astronomical objects into categories on the basis of physical, morphological, or evolutionary characteristics.
modified: 2020-12-04T02:45:15.161Z
contributor: AAS Frey.Katie Admin
modified: 2020-10-26T20:03:02.062Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T20:03:02.029Z
contributor: AAS Frey.Katie

Close binary stars
type: Concept
alternative label: Close binaries
broader: Binary stars
narrower: Z Andromedae stars
narrower: Compact binary stars
narrower: Ellipsoidal variable stars
narrower: Interacting binary stars
definition: A binary system in which the separation of the component stars is comparable to their diameters, so that they influence each other's evolution most commonly by the tidal forces.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:00:01.649Z
editorial note: Definition Provenance
  created: 2020-10-26T20:05:41.467Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-26T20:05:41.497Z
contributor: AAS Frey.Katie

Close encounters
type: Concept
broader: Celestial mechanics
narrower: Opik theory
related: Near-Earth objects
definition: In a star cluster, coming across of two stars so closely that their orbits alter by their mutual gravitational attractions. As regards an asteroid or comet, a situation when it crosses the Moon's orbit and approaches the Earth with a risk of collision.
contributor: AAS Frey.Katie
modified: 2020-10-26T20:06:31.917Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T20:06:47.512Z
  creator: AAS Frey.Katie
modified: 2020-10-26T20:06:47.541Z

Closed universe
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
definition: A cosmological model, first formulated by Friedmann and Lemaître, in which the Universe has a finite size and lifetime and space has a positive curvature, e.g. a Universe with a density greater than the critical density.
modified: 2020-11-03T19:25:11.726Z
modified: 2020-11-03T19:25:23.855Z
editorial note: Definition Provenance
  created: 2020-11-03T19:25:23.827Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Cloud monitors
type: Concept
broader: All-sky cameras

Earth's clouds
type: Concept
broader: Earth atmosphere
definition: A visible mass of water droplets and/or ice particles in the atmosphere above the Earth's surface.
contributor: AAS Frey.Katie Admin
alternative label: Clouds
broader: Atmospheric clouds
modified: 2020-12-16T19:54:05.427Z
modified: 2020-10-26T20:07:30.473Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T20:07:30.433Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

CMBR detectors
type: Concept
alternative label: Cosmic microwave background radiation detectors
broader: Astronomical detectors
related: Cosmic microwave background radiation

Almanacs
type: Concept
alternative label: Almanachs
broader: Astronomical reference materials
narrower: Nautical almanacs
definition: A book of tables, usually covering a period of one calendar year, that lists the future positions of the Moon, planets, and other prominent celestial objects, together with other useful astronomical data.
modified: 2020-11-04T22:11:03.874Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-04T22:11:15.153Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T22:11:15.186Z

CN stars
type: Concept
alternative label: Carbon-nitrogen stars
broader: Giant stars

CNO anomaly
type: Concept
broader: Solar physics

CO line emission
type: Concept
broader: Interstellar line emission

Cocoon stars
type: Concept
broader: Protostars
related: OH/IR stars
related: Red giant stars
related: Red supergiant stars
related: Hydroxyl sources
related: Infrared sources
definition: A star hidden in a dense envelope of gas and dust which is a strong source of infrared emission.
modified: 2020-10-26T20:07:57.538Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T20:08:09.076Z
  creator: AAS Frey.Katie
modified: 2020-10-26T20:08:09.101Z

Coelostats
type: Concept
broader: Stellar tracking devices
definition: A flat mirror with a clock-drive mounted in such a way that it moves from east to west to compensate for the apparent rotation of the Earth in order that the image of a particular area of sky remains fixed in the focal plane.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:09:25.582Z
modified: 2020-11-02T16:09:41.278Z
editorial note: Definition Provenance
  created: 2020-11-02T16:09:41.236Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Cold dark matter
type: Concept
broader: Dark matter
contributor: AAS Frey.Katie
definition: Any hypothetical non-baryonic dark matter that is non-relativistic at the point of decoupling in the early Universe. CDM plays a key role in cosmic structure formation.
modified: 2020-11-03T19:27:45.013Z
editorial note: Definition Provenance
  created: 2020-11-03T19:27:58.142Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:27:58.170Z

Cold neutral medium
type: Concept
alternative label: CNM
broader: Interstellar phases

Collapsing clouds
type: Concept
alternative label: Cloud collapse
broader: Molecular clouds

Collimation
type: Concept
alternative label: Collimated light
broader: Astronomical optics
contributor: AAS Frey.Katie
definition: To pack and align photons or atomic particles parallel to a particular direction.
modified: 2020-11-03T19:28:29.531Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T19:28:39.395Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:28:39.429Z

Color equation
type: Concept
broader: Photometric systems
contributor: AAS Frey.Katie Admin
preferred label: Colour equation
modified: 2021-08-24T15:19:22.667Z

Rapidly oscillating Ap star
type: Concept
broader: Magnetic variable stars
alternative label: roAp stars
alternative label: Alpha2 Canum Venaticorum stars
broader: Ap stars
alternative label: Alpha2 CVn stars
contributor: AAS Frey.Katie
definition: A chemically peculiar star characterized by the presence of high-frequency non-radial oscillations, with periods that range between about 4 and 16 min. These variations have periods from about 5 to 20 minutes and low amplitudes (B < 10 mmag). They are consistent with acoustic (p mode) pulsations of low degree and high radial overtone.
modified: 2020-11-17T20:15:27.851Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-17T20:15:37.803Z
modified: 2020-11-17T20:15:37.829Z

Coma Cluster
type: Concept
broader: Galaxy clusters
contributor: AAS Frey.Katie
alternative label: Abell 1656
definition: The nearest rich cluster of galaxies which contains more than a thousand known galaxies, is about 20 million light-years in diameter, and lies about 280 million light-years away in the constellation Coma Berenices.
modified: 2020-11-03T19:29:10.928Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T19:29:21.982Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:29:22.014Z

Comae
type: Concept
broader: Comets
editorial note: Needs disambiguation or creation of at least two separate terms. Wikipedia, Coma (cometary): "In astronomy, a coma (from the Greek κόμη, "hair") is the nebulous envelope around the nucleus of a comet." WIkipedia, Coma (optics): "In optics (especially telescopes), the coma (aka comatic aberration) in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components which results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration." -BG
definition: The nebulous envelope around the nucleus of a comet, formed when the comet passes close to the Sun.
alternative label: Comas
narrower: Ionized coma gases
narrower: Neutral coma gases
narrower: Coma dust
alternative label: Cometary atmospheres
alternative label: Comet atmospheres
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:41:01.110Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T19:32:04.654Z
modified: 2020-11-03T19:32:04.684Z

Comet interiors
type: Concept
contributor: AAS Frey.Katie
alternative label: Cometary interiors
broader: Comet nuclei
modified: 2019-12-13T21:38:51.536Z

Comet tail streamers
type: Concept
broader: Comet tails

Comet tails
type: Concept
broader: Comets
narrower: Comet tail streamers
definition: A formation of gas and/or dust that streams away from the coma of many comets under the influence of the Sun's radiation pressure and the solar wind.
contributor: AAS Frey.Katie
modified: 2020-10-26T20:12:21.840Z
narrower: Comet dust tails
narrower: Comet ion tails
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T20:12:37.249Z
modified: 2020-10-26T20:12:37.273Z

Cometary globules
type: Concept
broader: Dark interstellar clouds
definition: A relatively small cloud of dust and gas in the interstellar medium shaped like a comet with a bright-rimmed head. Cometary globules are situated near young massive stars with a strong stellar wind. The wind ionizes gases on the side facing the O stars and sweep away the low-density gas toward the tail. Cometary globules are believed to be molecular cloud condensations, which are so dense that they are not disrupted when an H II region expands into the molecular cloud surrounding it. The Rosette nebula is a good example of an H II region which shows an abundance of cometary globules.
modified: 2020-11-05T15:36:05.939Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-05T15:36:20.330Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-05T15:36:20.378Z

Ionized coma gases
type: Concept
contributor: AAS Frey.Katie Admin
alternative label: Cometary ionospheres
broader: Comae
preferred label: Ionised coma gases
modified: 2021-09-27T15:43:43.457Z

Cometary nebulae
type: Concept
alternative label: Cometary nebulas
broader: Nebulae
broader: Protostars

Alt-azimuth mounts
type: Concept
alternative label: Alt-azimuth mounting
alternative label: Altazimuth
alternative label: Altazimuth mountings
alternative label: Altazimuth mounts
alternative label: Altitude-azimuth
alternative label: Altitude-elevation mounts
alternative label: Azimuth mounting
broader: Telescope mounts
related: Azimuth
contributor: AAS Frey.Katie
definition: A telescope mounting which has its two axes of movement aligned with the horizon and the zenith.
modified: 2020-11-03T17:49:53.013Z
modified: 2020-11-03T17:50:06.785Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T17:50:06.760Z

Comets
type: Concept
broader: Small Solar System bodies
narrower: Short period comets
narrower: Comae
narrower: Comet tails
narrower: Long period comets
related: Astrophysical masers
related: Interplanetary medium
narrower: Dirty snowball model
narrower: Main-belt comets
narrower: Comet nuclei
definition: A small body of gas and dust which revolves around the Sun in a usually very elliptical or even parabolic orbit. It is seen to be composed of a head and often with a spectacular gaseous tail extending a great distance from the head. The rocky-icy head is called the comet nucleus. As the comet nears the Sun, the increased temperature causes the ice in the nucleus to sublimate and form a gaseous halo around the nucleus, called the coma. Comets often possess two tails, a dust tail that lies in the orbit behind the comet generated by surface activity, and a brighter, ionized gas tail, that points away from the Sun, driven by solar wind. Cometary reservoirs are thought to represent primordial solar system material. A comet with a dust coating on its surface that inhibits gas production might be classified as an asteroid. Because of this ambiguity, objects such as Chiron, Centaur asteroid, have been reclassified as comets. Comets are primarily composed of amorphous water ice, but also contain carbon dioxide, carbon monoxide, formaldehyde, methanol, methane at a few percent level (with respect to water), and many other molecules at a lower level.
narrower: Comet Halley
contributor: AAS Frey.Katie Admin
related: Near-Earth objects
example: 109P/Swift-Tuttle
example: P/Shoemaker-Levy 9
narrower: Near-sun comets
related: Interstellar objects
related: Comet origins
related: Comet dynamics
related: Exocomets
modified: 2022-06-24T15:13:49.760Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-10-26T20:16:23.802Z
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-26T20:16:23.830Z

Compact binary stars
type: Concept
alternative label: Compact object binaries
broader: Close binary stars
narrower: Binary pulsars
narrower: X-ray binary stars
broader: Interacting binary stars
definition: A binary star system which is composed of a collapsed object (degenerate dwarf, neutron star, or black hole) in orbit with a low-mass (≤ 0.5 M_sol) secondary star, wherein the collapsed star accretes matter from its companion. These two objects form a binary system of overall dimensions 10^6 km with an orbital period of only hours or less.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T18:55:27.225Z
contributor: AAS Frey.Katie
modified: 2020-10-26T20:17:53.114Z
editorial note: Definition Provenance
  created: 2020-10-26T20:17:53.088Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

AM Canum Venaticorum stars
broader: Cataclysmic variable stars
type: Concept
broader: Hydrogen deficient stars
related: DQ Herculis stars
alternative label: AM CVn stars
contributor: AAS Frey.Katie
definition: A binary system that has very short orbital period (less than one hour) and helium dominated spectrum. The prototype, AM Canum Venaticorum, with a period of 17 minutes, was discovered in 1967. AM CVn stars are semidetached binary systems in which accretion is going on. The donor star is hydrogen deficient and the accretor is usually a white dwarf. To fit within their Roche lobes, the donor stars must be dense, suggesting they may be degenerate too. It is at present thought that AM CVn stars represent three possible evolutionary phases in 1) double white dwarf systems, 2) white dwarf and helium star binaries, and 3) cataclysmic variables with evolved donors.
modified: 2020-10-26T18:33:44.144Z
modified: 2020-12-15T19:44:09.581Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-12-15T19:44:06.665Z
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin

Compact galaxies
type: Concept
broader: Galaxies
narrower: N galaxies
definition: A galaxy with no disk or nebulous background and a high surface brightness that appears only barely larger than a star-like point on a sky survey photograph.
contributor: AAS Frey.Katie
modified: 2020-10-26T20:21:07.643Z
editorial note: Definition Provenance
  created: 2020-10-26T20:21:36.212Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-26T20:21:36.236Z

Compact H II region
type: Concept
broader: H II regions
contributor: AAS Frey.Katie
definition: A Galactic H II region with an electron density ≥ 10^3 cm^-3 and of a linear dimension ≤ 1 pc.
modified: 2020-11-03T19:35:39.354Z
modified: 2020-11-03T19:35:52.066Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T19:35:52.034Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Compact nebulae
type: Concept
alternative label: Compact nebula
broader: Nebulae

Compact objects
type: Concept
alternative label: Compact stars
broader: Stellar remnants
narrower: Black holes
related: Compact radiation sources
contributor: AAS Frey.Katie
narrower: White dwarf stars
narrower: Neutron stars
definition: An astronomical object that is substantially denser or more compact than most objects of its class. More specifically, a neutron star or a stellar black hole.
modified: 2020-10-26T20:22:20.514Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T20:22:46.915Z
modified: 2020-10-26T20:22:46.951Z

Compact radiation sources
type: Concept
broader: Astronomical radiation sources
related: Compact objects

Alternatives to cosmic inflation
type: Concept
alternative label: Alternatives to inflation
broader: Cosmic inflation

Companion galaxies
type: Concept
broader: Galaxies

Companion stars
type: Concept
alternative label: Secondary stars
broader: Binary stars
narrower: Substellar companion stars
narrower: Tertiary stars
definition: The fainter of the two stars in a binary star system.
contributor: AAS Frey.Katie
modified: 2020-10-26T20:23:37.333Z
modified: 2020-10-26T20:23:50.660Z
editorial note: Definition Provenance
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T20:23:50.631Z

Comparison stars
type: Concept
broader: Standard stars
definition: A non-variable star used to monitor the variations of another nearby star.
modified: 2020-10-26T20:24:37.379Z
contributor: AAS Frey.Katie
modified: 2020-10-26T20:24:50.288Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T20:24:50.253Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Conical singularities
type: Concept
broader: Gravitational singularities

Conjunction
type: Concept
broader: Astronomical location
scope note: Refers to planet position
contributor: AAS Frey.Katie
definition: A position of two bodies in the solar system when they have the same celestial longitude, seen from the Earth. The bodies can be a planet and the Sun, two planets or the Moon and a planet. The superior planets are in conjunction with the Sun, when, seen from the Earth, they are right behind the Sun. The inferior planets, such as Mercury and Venus, have two conjunctions with the Sun: inferior conjunction, when they are between the Earth and the Sun, and superior conjunction, when they are on the other side of the Sun.
modified: 2020-11-03T19:39:03.840Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:39:14.771Z
  creator: AAS Frey.Katie
modified: 2020-11-03T19:39:14.798Z

Constellations
type: Concept
broader: Celestial sphere
definition: A grouping of conspicuous stars that, when seen from Earth, form an apparent pattern. The sky is divided into 88 constellations.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:20:09.273Z
modified: 2020-10-27T13:20:24.407Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-27T13:20:24.361Z
  creator: AAS Frey.Katie

Contact binary stars
type: Concept
narrower: W Ursae Majoris variable stars
contributor: AAS Frey.Katie
broader: Interacting binary stars
definition: A binary star system in which the two components are so close that they exchange gases in a complex manner. Their overlapping gravitational fields form a 'peanut' shaped equipotential surface.
modified: 2020-10-27T13:21:07.406Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-27T13:21:27.708Z
  creator: AAS Frey.Katie
modified: 2020-10-27T13:21:27.738Z

A dwarf stars
type: Concept
alternative label: A dwarfs
broader: A stars
alternative label: A-type dwarf stars
alternative label: A-type dwarfs
broader: Dwarf stars
modified: 2020-10-26T18:21:20.519Z
contributor: AAS Frey.Katie
modified: 2020-10-26T18:21:24.999Z

Altitude angle
type: Concept
alternative label: Elevation angle
broader: Horizontal coordinate system

Cool cores
type: Concept
broader: X-ray sources

Cool intergalactic medium
type: Concept
broader: Intergalactic medium phases
narrower: Cooling flows

Core-collapse supernovae
type: Concept
alternative label: Core collapse supernova
alternative label: Core collapse supernovae
alternative label: Core-collapse supernova
broader: Supernovae
narrower: Type Ib supernovae
narrower: Type Ic supernovae
narrower: Type II supernovae
definition: A supernova arising from the core collapse of a massive star.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T20:32:02.882Z
editorial note: Definition Provenance
  created: 2020-11-05T20:32:20.062Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-05T20:32:20.099Z

Stellar coronae
type: Concept
alternative label: Coronas
broader: Stellar atmospheres
narrower: Stellar coronal dimming
narrower: Stellar coronal holes
narrower: Stellar coronal lines
narrower: Stellar coronal loops
narrower: Stellar coronal plumes
narrower: Stellar E corona
narrower: Stellar F corona
narrower: Stellar K corona
contributor: AAS Frey.Katie
alternative label: Coronae
related: Solar corona
modified: 2019-11-26T18:03:18.151Z

Stellar coronal holes
type: Concept
broader: Stellar coronae
related: Solar coronal holes
alternative label: Stellar M coronal regions
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:45:32.238Z

Solar coronal mass ejections
type: Concept
alternative label: CME
related: Stellar mass loss
related: Ejecta
related: Stellar coronal mass ejections
broader: Solar storm
contributor: AAS Frey.Katie Admin
definition: A huge eruption of material from regions of the solar corona in which the magnetic field is closed, but which suffer an extremely energetic disruption. Over the course of several hours up to 10,000 billion kg of this material is ejected into interplanetary space with a speed of as high as 3000 km/s. CMEs are most spectacularly observed by a white light coronagraph located outside Earth's atmosphere. Such observations from Skylab in the early 1970's were the first to reveal this phenomenon. CME's disrupt the flow of the solar wind and can produce intense electromagnetic disturbances that can severely damage satellites and disrupt power grids on Earth. When these ejections reach the Earth, they give rise to geomagnetic storms. The frequency varies with the solar cycle; during solar minimum they come at a rate of about one per week, and during maximum there is an average of about two or three per day.
modified: 2020-11-24T17:35:36.922Z
editorial note: Definition Provenance
  created: 2020-11-04T15:08:40.350Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T15:08:40.381Z

Coronagraphic imaging
type: Concept
alternative label: Coronographic detection
broader: Astronomical techniques
modified: 2022-06-30T15:03:47.511Z
alternative label: Coronographic imaging
alternative label: Coronagraphic detection
broader: High contrast techniques
contributor: AAS Frey.Katie Admin

Corotating streams
type: Concept
alternative label: Interplanetary co-rotating streams
alternative label: Interplanetary corotating streams
broader: Interplanetary physics

Cosmic anisotropy
type: Concept
broader: Cosmic microwave background radiation

Cosmic electrodynamics
type: Concept
alternative label: Cosmical electrodynamics
broader: Plasma astrophysics

Cosmic inflation
type: Concept
alternative label: Cosmological inflation
alternative label: Inflation (cosmology)
broader: Cosmology
narrower: Alternatives to cosmic inflation
narrower: E-folding time
narrower: Gravitational waves
definition: A brief exponential expansion of the Universe postulated to have occurred 10-35 seconds after the Big Bang, in response to the separation of the strong interaction from the electroweak interaction. This idea aims at explaining the flatness problem, the horizon problem, and the magnetic monopole problem.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:27:21.235Z
editorial note: Definition Provenance
  created: 2020-10-27T13:27:32.952Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-27T13:27:32.993Z

Cosmic isotropy
type: Concept
broader: Cosmic microwave background radiation

Cosmic magnetic fields theory
type: Concept
broader: Astrophysical magnetism

Cosmic ray astronomy
type: Concept
broader: Astronomical methods
related: Cosmic rays

Cosmic ray detectors
type: Concept
broader: Astronomical detectors

Cosmic ray nucleosynthesis
type: Concept
broader: Nucleosynthesis

Cosmic ray showers
type: Concept
alternative label: Air shower
alternative label: Auger shower
broader: Cosmic rays

Cosmic ray sources
type: Concept
alternative label: Cosmic ray objects
broader: Cosmic rays

Cosmic rays
type: Concept
alternative label: Cosmic radiation
alternative label: Primary cosmic ray
broader: Astronomical radiation sources
broader: Particle astrophysics
narrower: Secondary cosmic rays
narrower: Ultra-high-energy cosmic radiation
narrower: Cosmic ray showers
narrower: Cosmic ray sources
narrower: Forbush effect
narrower: Galactic cosmic rays
narrower: High-energy cosmic radiation
related: Cosmic ray astronomy
definition: Extremely energetic atomic nuclei which travel through the Universe at practically the speed of light and strike the Earth from all direction. Almost 90% of all the incoming primary cosmic rays are protons, about 9% are helium nuclei (alpha particles) and about 1% are electrons (beta minus particles). Some cosmic rays come from the Sun (mainly due to solar flares), most come from galactic supernovae, and a few with the highest energy are suspected to originate from outside the Milky Way. As for their flux, about 1 charged particle per second per cm^2 impacts the Earth. The typical kinetic energy of these particles is about 10 MeV/nucleon to several GeV/nucleon, although there are some at higher energies. In fact, the cosmic ray with the highest energy has been measured above x 10^20 eV. These ultra-high energy cosmic rays are suspected to be extragalactic, as there is no plausible mechanism of acceleration to these energies by a supernova, for example. Again, compare these energies to those of solar neutrinos that have only 0.26 MeV. Cosmic rays may be divided into primary cosmic rays and secondary cosmic rays. Their energy ranges from 10^9 to 10^20 electron-volts.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:16:35.629Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:42:05.763Z
  creator: AAS Frey.Katie
modified: 2020-11-03T19:42:05.791Z
contributor: AAS Frey.Katie

Am stars
type: Concept
alternative label: Metallic line stars
alternative label: Metallic-line stars
broader: Chemically peculiar stars
broader: A stars
broader: Magnetic stars
broader: Magnetic variable stars
contributor: AAS Frey.Katie
alternative label: Am-type stars
definition: A chemically peculiar A- or early F-type star showing an overabundance of heavy elements and an underabundance of calcium and scandium. An Am star cannot receive a unique spectral type, as different methods (using the metallic lines, the hydrogen Balmer lines, and the calcium Ca II K-lines) yield three different spectral types. Contrarily to Ap stars, Am stars do not have significant external magnetic fields. Their rotational velocities are about 100-120 km s-1 smaller than those of Ap stars.
modified: 2020-11-03T17:57:19.707Z
modified: 2020-11-03T17:57:39.528Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T17:57:39.501Z

Cosmic web
type: Concept
broader: Large-scale structure of the universe
narrower: Galaxy cluster counts
narrower: Voids
contributor: AAS Frey.Katie
definition: The entire, large-scale structure of the Universe in which galaxy clusters are connected by cosmic filaments (made up of dark matter and baryons) in a spongelike geometry, while the low-density voids are connected to each other by low-density tunnels.
modified: 2020-11-03T19:44:02.483Z
editorial note: Definition Provenance
  created: 2020-11-03T19:44:14.539Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T19:44:14.568Z

Cosmochemistry
type: Concept
alternative label: Chemical cosmology
alternative label: Cosmic chemistry
broader: Astrochemistry
broader: Cosmology
narrower: Cosmochronology
related: Cosmic abundances
contributor: AAS Frey.Katie
definition: The study of the chemical composition of the universe and the processes that produced those compositions. Cosmochemistry is an interdisciplinary science that overlaps with geochemistry, geology, astronomy, astrophysics, and geophysics.
modified: 2020-11-03T19:46:54.568Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:47:04.617Z
  creator: AAS Frey.Katie
modified: 2020-11-03T19:47:04.641Z

Cosmogony
type: Concept
alternative label: Cosmogeny
broader: Cosmology
related: Solar system
contributor: AAS Frey.Katie
definition: A philosophical, religious, or mythical story of the creation or origin of the Universe, usually referring to the solar system.
modified: 2020-11-03T19:47:31.736Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T19:47:42.770Z
modified: 2020-11-03T19:47:42.797Z

Cosmological constant
type: Concept
alternative label: Lambda
broader: Observational cosmology
broader: Dark energy
narrower: Cosmological constant experiments
contributor: AAS Frey.Katie
definition: A term introduced by Einstein into his gravitational field equations in order to allow a solution corresponding to a static Universe. The cosmological constant is physically interpreted as due to the vacuum energy of quantized fields.
modified: 2020-11-03T19:48:11.470Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T19:48:20.987Z
modified: 2020-11-03T19:48:21.016Z

Cosmological constant experiments
type: Concept
broader: Cosmological constant

Cosmological evolution
type: Concept
alternative label: Astronomical evolution
broader: Cosmology
narrower: Orbital evolution
narrower: Dynamical evolution
narrower: Galaxy evolution

Cosmological neutrinos
type: Concept
broader: Particle astrophysics

Cosmological parameters
type: Concept
broader: Cosmology
narrower: Sigma8
narrower: Cosmological parameters from large-scale structure
narrower: Curved space
narrower: Dark energy
narrower: Deceleration parameter
narrower: Density parameters
narrower: Flat space
narrower: Hubble constant
narrower: Hubble time

Amateur astronomers
type: Concept
broader: Astronomical research
related: Amateur astronomy
contributor: AAS Frey.Katie
definition: A person who engages in astronomy as a pastime rather than as a profession.
modified: 2020-10-26T18:38:05.301Z
modified: 2020-10-26T18:38:17.565Z
editorial note: Definition Provenance
  created: 2020-10-26T18:38:17.538Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Cosmological parameters from large-scale structure
type: Concept
alternative label: Cosmological parameters from LSS
alternative label: Cosmological parameters from large scale structure
broader: Cosmological parameters

Cosmological perturbation theory
type: Concept
broader: Big Bang theory
related: Perturbation methods

Cosmological phase transitions
type: Concept
broader: Cosmology

Cosmology
type: Concept
alternative label: Physical cosmology
narrower: Non-Gaussianity
narrower: Observational cosmology
narrower: Origin of the universe
narrower: Plasma astrophysics
narrower: Quantum cosmology
narrower: Radiative transfer
narrower: Redshifted
narrower: Relativistic cosmology
narrower: Bianchi cosmology
narrower: Big Bang theory
narrower: Brane cosmology
narrower: Cosmic inflation
narrower: Cosmogony
narrower: Cosmological evolution
narrower: Cosmological models
narrower: Cosmological parameters
narrower: Cosmological phase transitions
narrower: Anthropic principle
narrower: Hierarchical cosmology
narrower: Astronomical radiation sources
narrower: Large-scale structure of the universe
narrower: Astrophysical dust processes
related: Protogalaxies
related: Dark matter
top concept of: The Unified Astronomy Thesaurus
narrower: Cosmochemistry
definition: The science of the origin, structure, and evolution of the Universe including the origin of galaxies, the chemical elements, and matter.
contributor: AAS Frey.Katie Admin
modified: 2020-12-03T21:01:18.958Z
narrower: Cosmological principle
contributor: AAS Frey.Katie
modified: 2020-11-03T19:49:02.325Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T19:49:02.294Z

Curvature singularities
type: Concept
broader: Gravitational singularities

Curved space
type: Concept
broader: Cosmological parameters

D galaxies
type: Concept
broader: Elliptical galaxies
narrower: cD galaxies

D layer
type: Concept
alternative label: D region
broader: Earth ionosphere

DA stars
type: Concept
broader: White dwarf stars
alternative label: DA white dwarf
contributor: AAS Frey.Katie Admin
alternative label: DA white dwarf stars
definition: A white dwarf whose spectrum shows the Balmer lines of hydrogen only, with no helium or metals.
modified: 2020-11-04T21:12:50.781Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:14:20.292Z
modified: 2020-11-04T21:14:20.320Z

Damped Lyman-alpha systems
type: Concept
broader: Intergalactic clouds

Amateur astronomy
type: Concept
alternative label: Backyard astronomy
alternative label: Stargazing
broader: Astronomical methods
narrower: Night vision
narrower: Purkinje effect
contributor: AAS Frey.Katie
related: Amateur astronomers
definition: The astronomical activities carried out by amateur astronomers.
modified: 2020-10-26T18:38:34.386Z
modified: 2020-10-26T18:38:44.540Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T18:38:44.517Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Dark adaption
type: Concept
alternative label: Dark adaptation
alternative label: Retinal adaption
broader: Astronomical optics
contributor: AAS Frey.Katie
definition: The automatic adjustment of the iris and retina of the eye to allow maximum vision in the dark, following exposure of the eye to a relatively brighter illumination.
modified: 2020-11-03T19:49:33.479Z
editorial note: Definition Provenance
  created: 2020-11-03T19:49:47.785Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:49:47.815Z

Dark energy
type: Concept
broader: Cosmological parameters
narrower: Quintessence
narrower: Cosmological constant
contributor: AAS Frey.Katie Admin
modified: 2020-11-06T02:02:15.493Z
definition: A hypothetical form of energy that fills all the space and tends to increase the rate of expansion of the Universe. Assuming the existence of dark energy is a way to explain recent observations that the Universe appears to be expanding at an increasing rate. Dark energy seems to be a kind of anti-gravity force and is supposed to be related to vacuum energy. Where gravity pulls things together at the more local level, dark energy tears them apart on the grander scale. The acceleration equation, one of Einstein's equations for the homogeneous Universe, indicates that if the Universe is accelerating, the pressure of the driving component should be strongly negative. The first indication of dark energy was provided by the observation of Type Ia supernovae. Other probes of dark energy are: baryon acoustic oscillations, weak gravitational lensing, and clusters of galaxies. In the standard model of cosmology, dark energy currently accounts for almost 74% of the total mass-energy of the Universe. Two proposed forms for dark energy are the cosmological constant and exotic component such as quintessence.
modified: 2020-11-03T19:51:11.129Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T19:51:11.102Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Dark interstellar clouds
type: Concept
alternative label: Absorption nebula
alternative label: Absorption nebulae
alternative label: Dark clouds
alternative label: Dark nebula
alternative label: Dark nebulae
broader: Nebulae
broader: Interstellar clouds
narrower: Bok globules
narrower: Cometary globules
narrower: Infrared dark clouds

Dark matter
type: Concept
broader: High energy astrophysics
broader: Intergalactic medium
narrower: Baryonic dark matter
narrower: Warm dark matter
narrower: Cold dark matter
narrower: Hot dark matter
related: Navarro-Frenk-White profile
related: Cosmology
related: Particle astrophysics
contributor: AAS Frey.Katie
modified: 2020-11-03T19:51:46.777Z
definition: Matter that has no radiation and therefore cannot be detected directly, but whose presence can be inferred from dynamical phenomena produced by its gravitational influence. The existence of dark matter is deduced mainly from the rotational speeds of galaxies, velocities of galaxies in clusters, gravitational lensing by galaxy clusters, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter plays also a central role in cosmic structure formation. There exists a large number of non-baryonic dark matter candidates. They include, the hypothetical stable particles WIMPs, neutralinos, axions, gravitinos, etc. Among unstable candidates are gravitinos with mild R-parity violation and sterile neutrinos.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T19:51:56.811Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:51:56.838Z

Dark matter density
type: Concept
broader: Density parameters

Dark matter detectors
type: Concept
broader: Astronomical detectors

Dark matter distribution
type: Concept
broader: Large-scale structure of the universe

DB stars
type: Concept
broader: White dwarf stars
broader: Helium-rich stars
definition: A white dwarf whose spectrum shows strong He I in the absence of hydrogen or metal lines.
contributor: AAS Frey.Katie Admin
alternative label: DB white dwarf
modified: 2020-11-04T21:13:27.898Z
alternative label: DB white dwarf stars
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:13:38.662Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T21:13:38.692Z

DDO classification
type: Concept
alternative label: Van den Bergh classification
alternative label: Van den Bergh classification of galaxies
broader: Galaxy classification systems

Amor group
type: Concept
alternative label: Amor asteroids
broader: Near-Earth objects
definition: A near-Earth asteroid (NEA) with perihelion distances between 1.017 and 1.3 astronomical units. The Amor asteroids approach the orbit of the Earth from beyond, but do not intersect it. Most Amors do cross the orbit of Mars. It is estimated that 32% of the total number of NEAs are Amors. One of the larger Amors is Eros.
narrower: Eros
contributor: AAS Frey.Katie Admin
modified: 2020-12-03T17:23:52.817Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-26T18:37:33.837Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-26T18:37:33.864Z
contributor: AAS Frey.Katie

DDO photometry
type: Concept
broader: Medium band photometry
alternative label: DDO photometric system
modified: 2020-10-21T18:32:00.695Z
contributor: AAS Frey.Katie

de Sitter universe
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
definition: A solution to Einstein's field equations of general relativity which contains no ordinary matter (Ω_M = 0) or radiation (Ω_R = 0), is Euclidean (k = 0), but has a cosmological constant (Ω_Λ > 0). The Universe expands exponentially forever. This solution was the first model expanding of expanding Universe.
modified: 2020-11-03T19:52:34.711Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:52:45.267Z
modified: 2020-11-03T19:52:45.296Z

De Vaucouleurs Sandage classification
type: Concept
alternative label: De Vaucouleurs system
alternative label: De Vaucouleurs-Sandage classification
broader: Galaxy classification systems
related: Spiral arms
related: Spiral galaxies
related: Elliptical galaxies
related: Irregular galaxies
related: Lenticular galaxies

Debris disks
type: Concept
alternative label: Debris discs
broader: Circumstellar disks
narrower: Planetesimals
narrower: Exozodiacal dust

Deceleration parameter
type: Concept
alternative label: Q-parameter
broader: Cosmological parameters
narrower: Accelerating universe
contributor: AAS Frey.Katie
definition: A parameter designating the rate at which the expansion of the Universe would slow down owing to the braking gravitational effect of the matter content of the Universe.
modified: 2020-11-03T19:53:17.374Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T19:53:32.012Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T19:53:32.051Z

Declination
type: Concept
alternative label: Celestial latitude
broader: Equatorial coordinate system
contributor: AAS Frey.Katie
definition: Angular distance (symbol δ) from the celestial equator. One of the coordinates, with right ascension, that defines the position of a heavenly body in the equator system. Declination is measured positively (+) north or negatively (-) south of the celestial equator from 0° to 90°.
modified: 2020-11-03T19:54:18.279Z
modified: 2020-11-03T19:54:27.957Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T19:54:27.930Z

Deep space probes
type: Concept
alternative label: Deep-space probes
broader: Space probes

Degenerate matter
type: Concept
broader: Stellar remnants
contributor: AAS Frey.Katie
definition: Highly compressed matter in which the normal atomic structure has broken down and which, because of quantum-mechanical effects, exerts a pressure that is independent of temperature. Bodies with masses less than Chandrasekhar's limit (1.4 solar masses) are supported by electron degeneracy pressure and have densities of about 10^6 kg/m^3. In collapsed stars of mass above 1.4 solar masses, gravity will overwhelm electron degeneracy and further collapse ensues. Electrons combine with protons to form neutrons, so producing a neutron star. Because neutrons, like electrons, are fermions and therefore subject to the Pauli exclusion principle, at high enough densities, about 10^14 kg/m^3, neutron degeneracy pressure prevents further collapse of the star. For masses larger than 2-3 solar masses, even neutron degeneracy cannot prevent further collapse, and a black hole is formed.
modified: 2020-11-03T20:04:27.018Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T20:04:37.173Z
modified: 2020-11-03T20:04:37.202Z

Delta Cepheid variable stars
type: Concept
broader: Cepheid variable stars
alternative label: Delta Cephei stars
alternative label: Delta Cepheids
alternative label: Delta Cephei variables
alternative label: Population I Cepheids
alternative label: Type I Cepheids
definition: The prototype of classical Cepheid variables, which is a pulsating yellow supergiant. John Goodricke was the first in 1784 to discover its variability. The star shows a quick and sharp rise from minimum to maximum, and slowly declines to its minimum again. The changes in brightness are accompanied by and principally caused by changes in stellar temperature and also by changes in radius. δ Cephei was actually the second Cepheid variable to be discovered. The first one, Eta Aquilae, had been discovered earlier the same year by Edward Pigott. δ Cephei varies with a period of 5.366341 days (or 5 days 8 hours 37.5 minutes) from magnitude 3.48, spectral type F5 Ib in its maximum to magnitude 4.37, spectral type G2 Ib in its minimum. It lies at a distance of 1,340 light-years.
modified: 2020-11-05T15:47:55.117Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T15:48:14.073Z
editorial note: Definition Provenance
  created: 2020-11-05T15:48:14.045Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Delta Scuti variable stars
type: Concept
alternative label: Al Velorum stars
alternative label: Delta Scuti variables
alternative label: Dwarf Cepheids
broader: Multi-periodic variable stars
broader: Pulsating variable stars
broader: Short period variable stars
contributor: AAS Frey.Katie Admin
definition: A member of a class of pulsating stars with periods less than 0.3 days, spectral types A or F, and visual light amplitudes in the range from a few thousands of a magnitude to about 0.8 mag. On the H-R diagram, δ Scuti stars form a group which lies in an instability strip which includes the classical Cepheids at its brightest end and the pulsating white dwarfs at its faintest limit. These stars can show very complex light variations since, while some of them are pulsating in one radial mode only, others may be pulsating simultaneously in several radial and non-radial modes.
modified: 2020-11-05T15:48:57.109Z
modified: 2020-11-05T15:49:10.009Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-05T15:49:09.979Z

Density parameters
type: Concept
broader: Cosmological parameters
narrower: Matter density
narrower: Baryon density
narrower: Dark matter density
narrower: Lambda density

Density wave model
type: Concept
alternative label: Density wave theory
broader: Galaxy formation

Descending node
type: Concept
alternative label: South node
broader: Orbital nodes
contributor: AAS Frey.Katie
definition: The point in an orbit where the orbiting body crosses a reference plane, such as the ecliptic or the celestial equator, going from north to south.
modified: 2020-11-03T20:09:09.006Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:09:18.439Z
  creator: AAS Frey.Katie
modified: 2020-11-03T20:09:18.472Z

Detached binary stars
type: Concept
broader: Binary stars
definition: A binary star system whose components are not in contact and in which no significant mass exchange is occurring.
modified: 2020-10-27T13:37:04.501Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-10-27T13:37:20.006Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-27T13:37:20.041Z

Detached objects
type: Concept
broader: Trans-Neptunian objects

Diamond ring effect
type: Concept
broader: Solar eclipses
contributor: AAS Frey.Katie
definition: An intense flash of light that happens a few seconds before and after totality during a solar eclipse. The effect is caused by the last rays of sunlight before totality (or the first rays of sunlight after totality) shining through valleys on the edge of the Moon.
modified: 2020-11-03T20:11:10.469Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T20:11:20.436Z
modified: 2020-11-03T20:11:20.466Z

Diffuse interstellar bands
type: Concept
broader: Astrochemistry
broader: Interstellar absorption
definition: Absorption features in the spectrum of stars identified in the ultraviolet, visible, and infrared regions. They have an interstellar origin, but despite extensive efforts, their carrier(s) have not yet been clearly identified.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:38:01.457Z
modified: 2020-10-27T13:38:17.664Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-27T13:38:17.624Z

Diffuse interstellar clouds
type: Concept
alternative label: Translucent interstellar clouds
broader: Interstellar clouds
definition: An interstellar cloud in which hydrogen is completely dissociated and which is less dense and dusty than molecular clouds. In diffuse interstellar clouds photoabsorption of the background ultraviolet (UV) radiation field is an important dissociating and ionizing process. Typical densities and temperatures of diffuse clouds are 10^2 to 10^3 cm^-3 and 20 to 100 K respectively. Because of modest extinctions (≤ 1 mag), photodissociation processes are important in diffuse clouds preventing the formation of larger molecules.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:39:05.772Z
modified: 2020-10-27T13:39:16.375Z
editorial note: Definition Provenance
  created: 2020-10-27T13:39:16.346Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Diffuse molecular clouds
type: Concept
broader: Molecular clouds
definition: A type of molecular cloud in which the interstellar radiation field is sufficiently attenuated, so that the local fraction of molecular hydrogen becomes substantial (> 0.1). However, enough interstellar radiation is still present to photoionize any atomic carbon, or to photodissociate carbon monoxide (CO) such that carbon is predominantly still in the form of C+ (> 0.5). In steady state, diffuse molecular clouds must necessarily be surrounded by diffuse atomic gas, in order to provide the shielding of radiation. This means that most sightlines that cross a diffuse molecular cloud will also cross diffuse atomic gas.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:40:31.904Z
editorial note: Definition Provenance
  created: 2020-10-27T13:40:42.969Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-27T13:40:42.993Z

Diffuse nebulae
type: Concept
alternative label: Diffuse nebula
broader: Nebulae
definition: An irregularly shaped and low density interstellar cloud visible in the optical wavelengths.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:41:06.585Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-27T13:41:17.567Z
  creator: AAS Frey.Katie
modified: 2020-10-27T13:41:17.595Z

Diffuse radiation
type: Concept
alternative label: Diffuse sky radiation
alternative label: Skylight
modified: 2019-12-12T21:44:23.913Z
broader: Earth atmosphere
contributor: AAS Frey.Katie
alternative label: Sky radiation
alternative label: Diffuse skylight
editorial note: Diffuse radiation
  comment: "Diffuse radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. Also called sky radiation, diffuse skylight, or just skylight, it is the determinative process for changing the colors of the sky." https://en.wikipedia.org/wiki/Diffuse_sky_radiation
  created: 2019-12-12T21:42:47.390Z
  creator: AAS Frey.Katie
modified: 2019-12-12T21:42:47.417Z

Diffuse x-ray background
type: Concept
broader: X-ray sources

Dirac cosmology
type: Concept
broader: Cosmological models

Direct detection interferometry
type: Concept
alternative label: Direct-detection interferometry
broader: Interferometry

Direct imaging
type: Concept
broader: Exoplanet detection methods
broader: Astronomical techniques
contributor: AAS Frey.Katie Admin
narrower: High contrast techniques
narrower: Far infrared interferometry
modified: 2022-06-30T15:03:59.704Z

Dirty snowball model
type: Concept
alternative label: Dirty snowball theory
broader: Comets
definition: A model for a cometary nucleus proposed by Fred Whipple (1950-51), according to which the nucleus is a solid body (a few kilometers across) made up of various ices (frozen water, methane, ammonia, carbon dioxide, and hydrogen cyanide) in which dust is embedded. Dust particles are liberated when the ices vaporize as the comet approaches the Sun, and they get blown away by solar radiation pressure, often forming impressive, gently curved dust tails.
contributor: AAS Frey.Katie Admin
alternative label: Dirty iceball model
modified: 2020-11-05T15:40:10.914Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T15:40:22.092Z
modified: 2020-11-05T15:40:22.120Z

Discrete radio sources
type: Concept
broader: Radio sources

Andromeda Galaxy
type: Concept
alternative label: M31
alternative label: Messier 31
alternative label: NGC 224
broader: Spiral galaxies
broader: Local Group
contributor: AAS Frey.Katie
definition: The nearest spiral galaxy to our own and a major member of the Local Group. It lies in the constellation Andromeda and is the most remote object normally visible to the naked eye. The earliest known reference to this galaxy is by the Iranian astronomer Sufi who called it 'the little cloud' in his Book of Fixed Stars (A.D. 964).
modified: 2020-11-03T17:40:10.991Z
modified: 2020-10-26T18:40:03.344Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:40:03.314Z

Disk flaring
type: Concept
alternative label: Disc flaring
broader: Stellar flares

Disk galaxies
type: Concept
alternative label: Disc galaxies
broader: Galaxies
narrower: Ring galaxies
narrower: Spiral galaxies
narrower: Lenticular galaxies
contributor: AAS Frey.Katie Admin
scope note: Refers to the specific shape and form of a particular classification of galaxies. Does not refer to the disk part of a galaxy (see "Galaxy disk").
definition: A galaxy consisting of a thin disk of stars and interstellar matter which may include spiral arms and bar.
modified: 2020-11-05T15:38:24.039Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T15:38:38.508Z
modified: 2020-11-05T15:38:38.539Z

Distance indicators
type: Concept
broader: Stellar distance

Distance measure
type: Concept
broader: Astrometry
narrower: Parsec
narrower: Light year
narrower: Astronomical unit

Diurnal parallax
type: Concept
broader: Parallax
narrower: Horizontal parallax
contributor: AAS Frey.Katie
alternative label: Geocentric parallax
definition: The apparent difference between the position of a celestial object measured from the Earth's surface and the position that would be recorded by a hypothetical observer at the center of the Earth.
modified: 2020-11-03T20:14:11.057Z
modified: 2020-11-03T20:14:27.019Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T20:14:26.987Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

DO stars
type: Concept
broader: White dwarf stars
narrower: PG 1159 stars
definition: A white dwarf whose spectrum shows strong lines of singly ionized helium He II; He I or H may be present. As a DO star cools, the He II will recombine with free electrons to form He I, eventually changing the DO type into a DB white dwarf.
contributor: AAS Frey.Katie Admin
alternative label: DO white dwarf
alternative label: DO white dwarf stars
modified: 2020-11-04T21:15:28.753Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:15:40.251Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T21:15:40.280Z

Dobsonian telescopes
type: Concept
broader: Newtonian telescopes

Domes
type: Concept
alternative label: Telescope dome
broader: Observatories
scope note: Excluding lunar dome
contributor: AAS Frey.Katie
definition: A vault, having a circular plan and usually in the form of a portion of a sphere, that shelters an optical telescope.
modified: 2020-11-03T20:15:04.500Z
modified: 2020-11-03T20:15:16.307Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:15:16.280Z
  creator: AAS Frey.Katie

Angular separation
type: Concept
alternative label: Angular distance
alternative label: Apparent distance
alternative label: Apparent separation
broader: Astronomical location
contributor: AAS Frey.Katie Admin
definition: Between two points A and B, the angle subtended by lines drawn from an observing point O to A and B.
modified: 2020-11-24T17:20:08.801Z
modified: 2020-11-24T17:20:20.689Z
editorial note: Definition Provenance
  created: 2020-11-24T17:20:20.653Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Doppler imaging
type: Concept
alternative label: Doppler-imaging
broader: Astronomical techniques
narrower: Zeeman-Doppler imaging

Doppler shift
type: Concept
alternative label: Doppler effect
broader: Astronomical techniques
narrower: Redshifted
narrower: Blueshifted
contributor: AAS Frey.Katie
definition: Effect of the relative motion of a wave source (light, sound) and the observer. If the source is moving away, the wavelength is stretched (shifted toward lower frequencies). If the source is approaching, the wavelength is compressed (shifted toward higher frequencies). These effects, known as Doppler shifts, are in the case of light waves called redshift and blueshift, respectively.
modified: 2020-11-03T20:18:43.377Z
modified: 2020-11-03T20:18:56.967Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:18:56.942Z

Double-mode Cepheid variable stars
contributor: AAS Frey.Katie
type: Concept
alternative label: Double-mode Cepheid stars
alternative label: Double-mode Cepheid variables
alternative label: Double-mode Cepheids
broader: Cepheid variable stars
broader: Double-mode variable stars
modified: 2019-12-03T17:56:24.774Z

Double-mode pulsation
type: Concept
alternative label: Double mode pulsation
broader: Multi-periodic pulsation

Double-mode variable stars
type: Concept
alternative label: Double mode variable stars
broader: Multi-periodic variable stars
broader: Pulsating variable stars
narrower: Double-mode Cepheid variable stars
narrower: UU Herculis stars
narrower: RRd variable stars
scope note: Not to be confused with "Double periodic variable stars."
contributor: AAS Frey.Katie
modified: 2019-12-03T17:56:31.693Z

Double galaxies
type: Concept
alternative label: Binary galaxies
broader: Galaxies
narrower: Dumbbell galaxies

Double quasars
type: Concept
broader: Quasars

Draco dwarf galaxy
type: Concept
broader: Dwarf galaxies
definition: A dwarf elliptical galaxy that is a satellite of our Galaxy and lies at a distance of about 250,000 light-years from the Galactic center. Its diameter is only about 3,500 light-years, and its absolute magnitude -8.6, making it the least luminous galaxy known.
modified: 2020-11-05T15:41:42.012Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T15:41:54.081Z
editorial note: Definition Provenance
  created: 2020-11-05T15:41:54.048Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Dredge-up
type: Concept
alternative label: Dredge up
broader: Late stellar evolution
contributor: AAS Frey.Katie
definition: A process by which the nucleosynthesis products inside a star are drawn to upper layers of the star.
modified: 2020-11-03T20:20:50.881Z
editorial note: Definition Provenance
  created: 2020-11-03T20:21:01.916Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T20:21:01.947Z

Annual equation
type: Concept
broader: Lunar theory
definition: An irregularity in the Moon's orbit, which can amount to 11 degrees in a period of one year. It results from the Sun's disturbing effect on the motion of the Moon due to varying distance between them.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T22:23:35.302Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T22:22:33.452Z
modified: 2020-11-04T22:22:33.478Z

Drift scan imaging
type: Concept
alternative label: Drift scans
broader: Astronomical techniques

Dumbbell galaxies
type: Concept
broader: Double galaxies

Dust continuum emission
type: Concept
alternative label: Infrared cirrus
broader: Interstellar emissions

Dust nebulae
type: Concept
alternative label: Dust nebula
broader: Nebulae

Dwarf elliptical galaxies
type: Concept
alternative label: Dwarf ellipticals
broader: Dwarf galaxies
narrower: Sculptor dwarf elliptical galaxy
alternative label: dEs
alternative label: dE
definition: A galaxy that is much smaller than other members of the elliptical class; it is designated as dE. A subtype of dwarf ellipticals is called a dwarf spheroidal galaxy (dSph). The basic characteristics of the class are low surface brightness and smooth light distribution. They range in luminosity from that of the faintest dSph galaxies M_V ~ -9 to about -17. In the Local Group there are 19 known dEs. They are very common in galaxy clusters.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:36:04.817Z
editorial note: Definition Provenance
  created: 2020-10-27T13:48:13.796Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-27T13:48:13.827Z
contributor: AAS Frey.Katie

Dwarf galaxies
contributor: AAS Frey.Katie
type: Concept
broader: Galaxies
narrower: Nucleated dwarf galaxies
narrower: Compact dwarf galaxies
narrower: Draco dwarf galaxy
narrower: Dwarf elliptical galaxies
narrower: Dwarf irregular galaxies
narrower: Dwarf spheroidal galaxies
definition: A small, low luminosity galaxy that is associated with a larger spiral galaxy and may make up part of a galactic halo. There are many of them in the Local Group, and often orbit around larger galaxies such as the Milky Way and the Andromeda Galaxy. There are three main types of them: dwarf elliptical galaxy (dE), dwarf irregular galaxy (dI), and dwarf spiral galaxy (dSA).
modified: 2020-10-27T13:46:03.564Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-27T13:46:15.256Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-27T13:46:15.284Z

Dwarf irregular galaxies
contributor: AAS Frey.Katie
type: Concept
alternative label: Dwarf irregular galaxy
alternative label: Dwarf irregulars
alternative label: Irregular dwarf galaxies
broader: Dwarf galaxies
broader: Irregular galaxies
definition: An irregular galaxy that is much smaller than other irregulars. Dwarf irregulars are generally metal poor and have relatively high fractions of gas. They are thought to be similar to the earliest galaxies that populated the Universe, and are therefore important to understand the overall evolution of galaxies.
modified: 2020-10-27T13:46:43.065Z
modified: 2020-10-27T13:46:56.025Z
editorial note: Definition Provenance
  created: 2020-10-27T13:46:55.991Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Dwarf novae
type: Concept
alternative label: Dwarf nova
alternative label: U Geminorum-type variable stars
broader: Novae
narrower: SU Ursae Majoris stars
narrower: SX Arietis variable stars
narrower: U Geminorum stars
narrower: WZ Sagittae stars
narrower: Z Camelopardalis stars
modified: 2020-11-05T15:43:28.710Z
definition: A class of novae and cataclysmic variables that have multiple observed eruptions. Their prototype is U Geminorum star. Optically, dwarf nova eruptions have amplitudes of 2-6 mag in V, a duration of a few to 20 days and a recurrence time-scale of weeks to years. Dwarf novae are thought to be semidetached binary stars consisting of a white dwarf primary accreting via Roche lobe overflow from a companion which is usually a late-type, generally main-sequence star. DN outbursts are usually attributed to the release of gravitational energy resulting from an instability in the accretion disk or by sudden mass transfers through the disk.
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T15:43:40.426Z
modified: 2020-11-05T15:43:40.454Z

Dwarf planets
type: Concept
alternative label: Solar system dwarf planets
narrower: Pluto
narrower: Ceres
alternative label: Dwarf planets (Solar system)
definition: A new category of astronomical objects in the solar system introduced in a resolution by the 26th General Assembly of the International Astronomical Union (IAU) on August 24, 2006. The characterizing properties are as follows: 1) It is in orbit around the Sun; 2) It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape; 3) It has not 'cleared the neighbourhood' around its orbit; and 4) It is not a satellite of a planet, or other non-stellar body. The property 3 reclassified Pluto from a planet to a dwarf planet because it has not cleared the neighborhood of its orbit (the Kuiper Belt). The largest known dwarf planets are: Eris, Pluto, Ceres, Makemake, and 2015 RR245.
contributor: AAS Frey.Katie Admin
example: Eris
example: Makemake
broader: Solar system
modified: 2020-12-16T20:28:20.647Z
modified: 2020-10-27T13:51:27.409Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-27T13:51:27.379Z
  creator: AAS Frey.Katie

Annual parallax
type: Concept
alternative label: Heliocentric parallax
broader: Parallax
contributor: AAS Frey.Katie Admin
definition: The difference in position of a star as seen from the Earth and Sun, i.e. the angle subtended at a star by the mean radius of the Earth's orbit around the Sun. Same as heliocentric parallax. Because the Earth revolves around the Sun, we observe the sky from a constantly moving position in space. Therefore, we should expect to see an annual effect, in which the positions of nearby objects appear to oscillate back and forth in response to our motion around the Sun. This does in fact happen, but the distances to even the nearest stars are so great that we need to make careful observations with a telescope to detect it. The annual parallax of the nearest star, Proxima Centauri, is 0.762 arcsec, which is too small for our acuity of vision.
modified: 2020-11-04T22:22:58.071Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T22:23:14.668Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T22:23:14.695Z

Dwarf spheroidal galaxies
type: Concept
alternative label: Dwarf spheroidals
broader: Dwarf galaxies
narrower: Sagittarius dwarf spheroidal galaxy
narrower: Ursa Minor dwarf spheroidal galaxy
narrower: Fornax dwarf spheroidal galaxy
definition: A subtype of dwarf ellipticals (dwarf elliptical galaxy), which are companion to the Milky Way and other similar galaxies. The first example of such objects was discovered by Harlow Shapley (1938) in the constellation Sculptor. 22 such galaxies are known currently to orbit the Milky Way and at least 36 exist in the Local Group of galaxies. Nearby galaxy clusters such as the Virgo, Fornax, Centaurus, and Coma clusters contain hundreds to thousands of individual dSph galaxies. These galaxies have very low surface brightnesses, as low as only 1% that of the sky background. They are also among the smallest, least luminous galaxies known. Most of the radiation from dSph galaxies is emitted by stars in the optical portion of the electromagnetic spectrum. The lack of strong emission lines, infrared, or radio emission suggests that these galaxies are generally devoid of interstellar medium. The velocities of stars within dSph galaxies are so high that them must be disrupting. However, the bulk of mass in these galaxies might be undetected. Dynamical models that include dark matter do adequately explain the velocity dispersion of the stars in all dSph systems. In the most extreme cases, only 1% of the mass of the galaxy is visible. Many of the Local Group dSph galaxies show evidence for star formation more recent than 10 Gyr.
contributor: AAS Frey.Katie
modified: 2020-10-27T13:49:52.859Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-27T13:50:05.491Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-27T13:50:05.519Z

Dynamical evolution
type: Concept
broader: Cosmological evolution

Dynamical friction
type: Concept
alternative label: Gravitational drag
broader: Gravitational interaction
contributor: AAS Frey.Katie
definition: The gravitational interaction between a relatively massive body and a field of much less massive bodies through which the massive body travels. As a result, the moving body loses momentum and kinetic energy. An example of dynamical friction is the sinking of massive stars to the center of a star cluster, a process called mass segregation. Dynamical friction plays an important role in stellar dynamics. It was first quantified by Chandrasekhar (1943).
modified: 2020-11-03T20:27:00.842Z
editorial note: Definition Provenance
  created: 2020-11-03T20:27:16.302Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T20:27:16.328Z

Dynamical parallax
type: Concept
broader: Parallax
modified: 2020-11-03T20:27:55.554Z
contributor: AAS Frey.Katie
definition: A method for deriving the distance to a binary star. The angular diameter of the orbit of the stars around each other and their apparent brightness are observed. By applying Kepler's laws and the mass-luminosity relation, the distance of the binary star can be calculated.
modified: 2020-11-03T20:28:10.562Z
editorial note: Definition Provenance
  created: 2020-11-03T20:28:10.537Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

E+A galaxies
type: Concept
broader: Early-type galaxies
broader: Post-starburst galaxies
contributor: AAS Frey.Katie Admin
definition: E+A galaxies have strong Balmer absorption lines typical of young stars, but lack optical emission features (e.g. O III 5007) typical of star-forming regions and have metallic absorption lines (e.g. Ca H and K) indicative of an older population of dwarf stars. The presence of two distinct stellar populations and morphological observations suggest that E+A galaxies are the product of a gas-rich galaxy merger.
modified: 2020-11-24T17:28:29.043Z
modified: 2020-11-12T20:12:35.102Z
editorial note: Definition Provenance
  comment: Astrobites Guide to Classification of Galaxies and AGNs
  creator: AAS Frey.Katie Admin
  created: 2020-11-12T20:12:35.066Z

E-folding time
type: Concept
broader: Cosmic inflation
contributor: AAS Frey.Katie
definition: The time within which the amplitude of an oscillation increases or decreases by a factor e (= 2.71828...).
modified: 2020-11-03T20:46:28.061Z
modified: 2020-11-03T20:46:47.160Z
editorial note: Definition Provenance
  created: 2020-11-03T20:46:47.131Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Stellar E corona
type: Concept
alternative label: E components
broader: Stellar coronae
contributor: AAS Frey.Katie
related: Solar E corona
alternative label: Stellar E coronal regions
modified: 2019-11-26T18:05:44.747Z

Early-type emission stars
type: Concept
alternative label: Early type emission stars
broader: Early-type stars
broader: Emission line stars
narrower: Oe stars
narrower: Oef stars
narrower: Of stars
narrower: Be stars
narrower: Wolf-Rayet stars
narrower: Ae stars

Early-type galaxies
type: Concept
alternative label: Early type galaxies
broader: Galaxies
narrower: E+A galaxies
contributor: AAS Frey.Katie
definition: In the Hubble classification, galaxies on the left part of the Hubble sequence. Early-type galaxies tend to have redder colors, higher average surface brightnesses, and lower neutral hydrogen content than late-type galaxies. This terminology is based on the obsolete and erroneous idea that elliptical and lenticular galaxies might be evolutionary precursors to spiral and barred spiral galaxies.
modified: 2020-10-30T19:03:54.677Z
editorial note: Definition Provenance
  created: 2020-10-30T19:15:35.452Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-30T19:15:35.496Z

Annular eclipses
type: Concept
broader: Eclipses
definition: A solar eclipse in which the Moon is close the apogee and is, therefore, too small to cover the whole disk of the Sun, leaving a visible edge or ring of sunlight. An annular eclipse can last for 12m 30s at the most.
contributor: AAS Frey.Katie
modified: 2020-10-26T18:40:43.142Z
modified: 2020-10-26T18:40:57.283Z
editorial note: Definition Provenance
  created: 2020-10-26T18:40:57.253Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Early astronomical instruments
type: Concept
alternative label: Early astronomical instrumentation
broader: Astronomical instrumentation
narrower: Orreries
narrower: Photoheliographs
narrower: Ptolemy stones
narrower: Stone circles
narrower: Zenith tubes
narrower: Armillary spheres
narrower: Astronomical sextants
related: Archaeoastronomy
narrower: Planispheres
narrower: Sundials
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:56:51.250Z

Early stellar evolution
type: Concept
broader: Stellar evolution

Early universe
type: Concept
broader: Origin of the universe
narrower: Neutrino decoupling
narrower: Photon decoupling
narrower: Primordial galaxies
narrower: Recombination (cosmology)
narrower: Baryogenesis
narrower: Baryon acoustic oscillations
narrower: Reionization
narrower: Inflationary universe
narrower: Initial conditions of the universe
narrower: Leptogenesis
contributor: AAS Frey.Katie
definition: A qualitative term used to describe a phase in the history of the Universe, from the Big Bang event to the apparition of the first structures (seeds of future galaxies), at a redshift around 30.
modified: 2020-11-03T20:28:49.332Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:29:00.092Z
modified: 2020-11-03T20:29:00.119Z

Earth-moon system
type: Concept
alternative label: Earth moon system
broader: Solar system astronomy
contributor: AAS Frey.Katie
definition: A physical system composed on the Earth and the Moon in which both objects directly influence each other. The total energy in the Earth-Moon system is conserved. The most notable influence that the two objects have on each other is tides.
modified: 2020-11-03T20:34:33.704Z
editorial note: Definition Provenance
  created: 2020-11-03T20:34:50.990Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T20:34:51.022Z

Earth atmosphere
type: Concept
alternative label: Terrestrial atmosphere
broader: Planetary atmospheres
narrower: Mesopause
narrower: Mesosphere
narrower: Atmospheric circulation
narrower: Ocean-atmosphere interactions
narrower: Atmospheric tides
narrower: Ozone layer
narrower: Stratopause
narrower: Stratosphere
narrower: Thermosphere
narrower: Tropopause
narrower: Troposphere
narrower: Earth's clouds
narrower: Exosphere
narrower: Humidity
narrower: Earth ionosphere
narrower: Land-atmosphere interactions
related: Atmospheric extinction
modified: 2022-06-21T18:19:17.357Z
narrower: Diffuse radiation
narrower: Earth's seasons
narrower: Greenhouse effect
contributor: AAS Frey.Katie Admin

Earth trojans
type: Concept
broader: Near-Earth objects
broader: Trojan asteroids

Earth (planet)
type: Concept
alternative label: Planet Earth
broader: Solar system terrestrial planets
related: The Moon
contributor: AAS Frey.Katie Admin
definition: The third planet from the Sun. At perihelion, it is 147,099,590 km from the Sun, and at aphelion it is 152,096.150 km, whereas its mean distance from the Sun (astronomical unit) is 149,598 x 10^6 km. Its orbital period is 365.2563 days (sidereal year) and its eccentricity 0.017. Other characteristics: axial inclination 23.44°; rotation period 23.934 h (sidereal day); mean density 5.52 g/cm^3; mass 5.974 x 10^24 kg; escape velocity 11.18 km/s; average albedo 0.37. The Earth's atmosphere consists of 78% nitrogen, 21% oxygen and 0.9% argon, plus carbon dioxide, hydrogen, and other gases in much smaller quantities. The atmospheric pressure at sea level is about 1,000 mbar. The surface average temperature is 15° C, but it varies, on the average, between -50° C (winter, Siberia) and up to + 40° C (summer, Sahara). Liquid water covers 71% of the surface. Over 5,000 active volcanoes have been registered throughout man's known history. The outer layer of the planet, the lithosphere, is covered with the crust. In the upper mantle and beneath the lithosphere, lies asthenosphere. Convection in the asthenosphere has caused plate tectonics motions and continent drifts. The densest layer of the Earth is its core, about 3000 km to 6400 km beneath the surface, consisting primarily of iron and nickel. This core is believed to be at the origin of the magnetic field, which reaches about 3 x 10^-5 tesla near the equator. It has only one natural satellite, the Moon.
modified: 2020-11-24T19:31:48.280Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:33:58.375Z
contributor: AAS Frey.Katie
modified: 2020-11-03T20:33:58.419Z

Anomalistic month
type: Concept
broader: Lunar theory
definition: The time interval of 27.554551 days (27d 13h 18m 33.2s), on average, between two successive passages of the Moon through the perigee of its orbit.
modified: 2020-11-04T22:24:16.219Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T22:24:28.977Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T22:24:28.945Z

Eccentric anomaly
type: Concept
broader: Orbital anomalies
contributor: AAS Frey.Katie
definition: Of a planetary orbit, the angle measured from the perihelion position, to the center of the circumscribing auxiliary circle, to the projected position of the planet on the circle.
modified: 2020-11-03T20:35:29.483Z
modified: 2020-11-03T20:35:39.276Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T20:35:39.246Z

Eccentricity
type: Concept
broader: Orbital elements
contributor: AAS Frey.Katie
definition: The amount by which the orbit deviates from circularity: e = c/a, where c is the distance from the center to a focus and a the semi-major axis. If e = 0, the orbit is a circle. If e < 1, the orbit is an ellipse, if e > 1 it is a hyperbola, and if e = 1 it is a parabola. The eccentricity is one of the six orbital elements that define a Keplerian orbit.
modified: 2020-11-03T20:36:11.071Z
modified: 2020-11-03T20:36:22.349Z
editorial note: Definition Provenance
  created: 2020-11-03T20:36:22.315Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Eclipses
type: Concept
broader: Syzygy
narrower: Partial eclipses
narrower: Penumbra
narrower: Baily's beads
narrower: Solar eclipses
narrower: Total eclipses
narrower: Umbra
narrower: Zone of totality
narrower: Annular eclipses
narrower: Antumbra
narrower: Lunar eclipses
definition: The passage of the shadow of a celestial body over the surface of another. The maximum number of solar and lunar visible eclipses occurring annually is seven; the minimum number is two, both being solar. Solar eclipses take place when the new Moon is close to an orbital node and on the same longitude with the Sun. At that moment either the umbra, antumbra, or the penumbra touches the Earth's surface. For an observer located in the umbra the eclipse is total, while for one placed in the antumbra it is annular. Annular eclipses occur around lunar apogee. An observer situated in the penumbra sees only a partial eclipse. A total or annular eclipse can be seen from a band with a width of 270 km at the most, around which, the much larger partiality zone extends. The Moon's shadow crosses the Earth from west to east at about 3,200 km/h. During total eclipses the Sun's disk is entirely covered and the solar corona can be seen. A solar eclipse can last up to 3h (between the first and the fourth contacts). Totality has a theoretical maximum duration of 7m 31s, but it is usually shorter. A lunar eclipse can be seen from any place on Earth where the Moon is above the horizon; it occurs when the full Moon passes through the central dark shadow of the Earth. The Earth's shadow is much wider than the Moon and this is why the lunar eclipses can last up to four hours (between the first and the fourth contact).
contributor: AAS Frey.Katie
modified: 2020-10-30T19:19:12.185Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:19:23.634Z
modified: 2020-10-30T19:19:23.665Z

Eclipsing binary minima timing method
type: Concept
broader: Timing variation methods

Eclipsing binary stars
type: Concept
alternative label: Eclipsing binaries
alternative label: Eclipsing stars
alternative label: Eclipsing variable stars
alternative label: Photometric binary stars
broader: Binary stars
broader: Extrinsic variable stars
narrower: Beta Lyrae stars
narrower: Upsilon Sagittarii stars
narrower: Algol variable stars
narrower: W Ursae Majoris variable stars
definition: A binary star in which one of the two stars passes in front of the other so that the system's total light periodically fades. The most famous eclipsing binary is Algol.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T15:45:03.900Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-05T15:45:14.379Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-05T15:45:14.407Z

Ecliptic coordinate system
type: Concept
contributor: AAS Frey.Katie Admin
broader: Astronomical coordinate systems
narrower: Ecliptic latitude
narrower: Ecliptic longitude
narrower: Ecliptic poles
alternative label: Ecliptic system
modified: 2022-06-21T19:56:15.906Z
definition: Coordinate system with the ecliptic as the fundamental plane.
narrower: Ecliptic
narrower: Zodiac
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:23:37.309Z
modified: 2020-10-30T19:23:37.338Z

Ecliptic latitude
type: Concept
broader: Ecliptic coordinate system
contributor: AAS Frey.Katie
definition: One of the two coordinates in the ecliptic system; the angle measured from the ecliptic, positive toward the north.
modified: 2020-11-03T20:38:29.461Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T20:38:41.417Z
modified: 2020-11-03T20:38:41.446Z

Ecliptic longitude
type: Concept
broader: Ecliptic coordinate system
contributor: AAS Frey.Katie
definition: One of the two coordinates in the ecliptic system; the angle measured eastwards along the ecliptic from 0° to 360°, with the origin at the vernal equinox.
modified: 2020-11-03T20:42:04.985Z
modified: 2020-11-03T20:42:15.552Z
editorial note: Definition Provenance
  created: 2020-11-03T20:42:15.514Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Ecliptic poles
type: Concept
broader: Ecliptic coordinate system
narrower: North ecliptic pole
narrower: South ecliptic pole
definition: Either of the two points on the celestial sphere that are 90° above and below the plane of ecliptic. The north ecliptic pole lies in Draco, and the south ecliptic pole in Dorado. Due to precession, the celestial pole moves in a circle around the ecliptic poles once every 25,800 years.
modified: 2020-10-30T19:24:10.405Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:24:22.356Z
modified: 2020-10-30T19:24:22.384Z

Effective temperature
type: Concept
broader: Astrometry
contributor: AAS Frey.Katie
definition: A measure of the surface temperature of a star derived from the total emitted energy, assuming that the star is a blackbody emitter.
modified: 2020-11-03T20:43:09.848Z
modified: 2020-11-03T20:43:19.177Z
editorial note: Definition Provenance
  created: 2020-11-03T20:43:19.144Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Ansae
type: Concept
alternative label: Ansa
broader: Planetary rings
definition: The 'handles,' or extremities, of planetary rings, especially Saturn's, as viewed from Earth.
modified: 2020-10-26T18:42:01.843Z
contributor: AAS Frey.Katie
modified: 2020-10-26T18:42:23.848Z
editorial note: Definition Provenance
  created: 2020-10-26T18:42:23.823Z
  creator: AAS Frey.Katie
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Einstein field equations
type: Concept
broader: General relativity

Einstein rings
type: Concept
broader: Gravitational lensing
narrower: Luminous arcs
contributor: AAS Frey.Katie
alternative label: Chwolson ring
alternative label: Einstein-Chwolson ring
definition: The apparent shape of a background source undergoing the effect of gravitational lensing as seen from Earth, provided that the source, the intervening lens, and the observer are in perfect alignment through Einstein radius.
modified: 2020-10-30T19:21:05.374Z
modified: 2020-10-30T19:21:17.094Z
editorial note: Definition Provenance
  created: 2020-10-30T19:21:17.062Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Einstein universe
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
alternative label: Einstein static Universe
definition: A cosmological model in which a static (neither expanding nor collapsing) Universe is maintained by introducing a cosmological repulsion force (in the form of the cosmological constant) to counterbalance the gravitational force.
modified: 2020-10-30T19:22:18.674Z
modified: 2020-10-30T19:22:31.112Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:22:31.087Z

Elliptical galaxies
type: Concept
alternative label: E galaxies
broader: Galaxies
narrower: D galaxies
narrower: Giant elliptical galaxies
related: De Vaucouleurs Sandage classification
related: Galaxy classification systems
related: Hubble classification scheme
definition: A galaxy whose structure is smooth without spiral arms and ellipsoidal in shape. Ellipticals are redder than spirals of similar mass. Giant ellipticals contain over 1012 solar masses, whereas dwarf ellipticals have masses as low as 107 solar masses.
modified: 2020-10-30T19:25:32.402Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:25:45.187Z
modified: 2020-10-30T19:25:45.221Z

Emerging flux tubes
type: Concept
broader: Astrophysical magnetism

Emission line galaxies
type: Concept
broader: Galaxies
narrower: Markarian galaxies
narrower: Seyfert galaxies
narrower: LINER galaxies

Antapex
type: Concept
broader: Solar motion
contributor: AAS Frey.Katie
alternative label: Solar antapex
definition: The direction in the sky (in the constellation Columba) away from which the Sun seems to be moving (at a speed of 19.4 km/s) relative to general field stars in the Galaxy.
modified: 2020-11-03T17:59:53.711Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:00:11.294Z
modified: 2020-11-03T18:00:11.321Z

Emission line stars
type: Concept
broader: Stellar types
narrower: Me stars
narrower: Mira variable stars
narrower: S Doradus stars
narrower: Symbiotic binary stars
narrower: T Tauri stars
narrower: X-ray stars
narrower: Z Andromedae stars
narrower: Early-type emission stars
narrower: Flash stars
narrower: Gamma Cassiopeiae stars
narrower: H-alpha stars
narrower: Luminous blue variable stars
contributor: AAS Frey.Katie Admin
narrower: Be stars
narrower: FU Orionis stars
modified: 2020-12-16T19:05:30.954Z

Emission nebulae
type: Concept
broader: Nebulae
narrower: Planetary nebulae
narrower: H II regions
related: Gaseous nebulae
related: Herbig-Haro objects
definition: An ionized nebula whose spectrum consists of emission lines.
contributor: AAS Frey.Katie
modified: 2020-10-30T19:27:34.836Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:27:47.783Z
modified: 2020-10-30T19:27:47.812Z

Ephemerides
type: Concept
broader: Astronomical reference materials
contributor: AAS Frey.Katie
definition: A table of computed positions occupied by a celestial body over successive intervals of time such as daily; plural ephemerides.
modified: 2020-11-03T20:50:48.668Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T20:50:59.119Z
modified: 2020-11-03T20:50:59.151Z

Equation of the center
type: Concept
alternative label: Equation of the centre
broader: Orbital motion
contributor: AAS Frey.Katie Admin
preferred label: Equation of centre
modified: 2021-08-24T15:25:45.815Z

Equator position
type: Concept
broader: Astrometry

Equatorial coordinate system
type: Concept
alternative label: Celestial coordinate
alternative label: Equatorial system
broader: Astronomical coordinate systems
narrower: Right ascension
narrower: Solstice
narrower: Celestial equator
narrower: Celestial poles
narrower: Celestial sphere
narrower: Declination
narrower: Equatorial zone
narrower: Equinox
narrower: Hour angle
definition: An astronomical coordinate system for indicating the positions of celestial objects on the celestial sphere. The system consists of two components, right ascension and declination. Right ascension is the angle between the vernal equinox and the point where the hour circle intersects the celestial equator. The right ascension is always measured eastward from the vernal equinox, in the units of hours, minutes, and seconds. Declination is the angle between the celestial equator and the position of the star measured along the star's hour circle. It is measured in degrees, minutes, and seconds north or south of the celestial equator. By definition, the vernal equinox is located at right ascension 0h and declination 0°. Equatorial coordinates change with time due to the precession of the Earth's rotation axis.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T18:58:04.073Z
narrower: Circumpolar
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T20:52:11.152Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie
modified: 2020-11-03T20:52:11.183Z

Equatorial mounts
type: Concept
alternative label: Equatorial mountings
broader: Telescope mounts
definition: A telescope mounting consisting of a polar axis pointed toward the celestial pole, and a declination axis supporting the instrument at right angles to the polar axis.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:51:26.738Z
contributor: AAS Frey.Katie
modified: 2020-10-30T19:36:43.162Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:36:43.125Z

Equatorial zone
type: Concept
broader: Equatorial coordinate system

Antarctic observatories
type: Concept
broader: Observatories

Equinox
type: Concept
broader: Equatorial coordinate system
narrower: Autumnal equinox
narrower: Vernal equinox
definition: One of the two points on the celestial sphere where the celestial equator intersects the ecliptic, that is when the apparent ecliptic longitude of the Sun is 0° or 180°. At equinox, the length of the day and the night are equal all over the globe. The equinox is not a fixed point; it moves due to precession and nutation. If only precession is considered, we deal with the mean equinox of date. If nutation is also taken into account, then we are concerned with the true equinox.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:23:08.874Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-03T20:56:19.057Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T20:56:19.087Z

Ergosphere
type: Concept
broader: Black hole physics
contributor: AAS Frey.Katie
modified: 2020-11-03T20:56:54.821Z
definition: The region between the event horizon and the stationary limit of a rotating Kerr black hole. It is possible for a particle falling inside the ergosphere to break into two parts, one of which will fall into the black hole and the other will come out.
modified: 2020-11-03T20:57:14.026Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T20:57:13.993Z

Eruptive phenomena
type: Concept
broader: Stellar evolution

Ethnoastronomy
type: Concept
definition: The study of the beliefs, interpretations, and practices of specific cultures regarding celestial objects or phenomena. Ethnoastronomy uses the tools and methodologies of ethnology in the study of astronomical conceptions.
broader: Cultural astronomy
narrower: Indigenous astronomy
alternative label: Sociology of astronomy
alternative label: Astrosociology
modified: 2024-06-20T13:23:24.763Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T20:59:43.913Z
contributor: AAS Frey.Katie
modified: 2020-11-03T20:59:43.943Z

Evaporating gaseous globules
type: Concept
broader: Interstellar clouds

Event horizons
type: Concept
broader: Black hole physics
broader: Gravitational singularities
definition: The surface surrounding a black hole with the property that any light ray emitted inside it cannot escape to the outer space because of the strength of the gravitational field. The radius of the event horizon is called the Schwarzschild radius.
modified: 2020-10-30T19:38:39.808Z
contributor: AAS Frey.Katie
modified: 2020-10-30T19:38:54.980Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:38:54.951Z

Anthropic principle
type: Concept
broader: Cosmology
contributor: AAS Frey.Katie
definition: The idea that the existence of life and, in particular, our presence as intelligent observers, constrains the nature of the Universe. It is an attempt to explain the observed fact that the fundamental constants of nature are just right or fine-tuned to allow the Universe and life to exist.
modified: 2020-11-03T18:01:00.689Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:01:12.686Z
  creator: AAS Frey.Katie
modified: 2020-11-03T18:01:12.716Z

Evolution equation
type: Concept
broader: General relativity

Evolved stars
type: Concept
alternative label: Post-main sequence stars
narrower: Subgiant stars
narrower: Supergiant stars
narrower: Giant stars
narrower: Hypergiant stars
broader: Stellar evolutionary types
related: Hertzsprung Russell diagram
definition: A star that has left the main sequence.
modified: 2020-10-30T19:39:27.494Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:39:43.696Z
modified: 2020-10-30T19:39:43.731Z

Natural satellites (Extrasolar)
type: Concept
broader: Exoplanet astronomy
contributor: AAS Frey.Katie
alternative label: Exomoons
related: Exoplanets
narrower: Irregular natural satellites (Extrasolar)
related: Natural satellites (Solar system)
definition: A natural satellite orbiting an extrasolar planet.
modified: 2020-11-10T19:38:58.530Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T19:39:08.145Z
  creator: AAS Frey.Katie
modified: 2020-11-10T19:39:08.170Z

Exoplanet astronomy
type: Concept
narrower: Planet hosting stars
narrower: Natural satellites (Extrasolar)
narrower: Exoplanet systems
narrower: Exoplanet catalogs
narrower: Exoplanet detection methods
narrower: Exoplanet dynamics
narrower: Exoplanet evolution
narrower: Exoplanet formation
narrower: Exoplanet structure
narrower: Exoplanets
top concept of: The Unified Astronomy Thesaurus
narrower: Exoplanet migration
narrower: Exocomets

Exoplanet catalogs
type: Concept
broader: Exoplanet astronomy
preferred label: Exoplanet catalogues
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:44:04.508Z

Exoplanet detection methods
type: Concept
alternative label: Exoplanet detection
alternative label: Extrasolar planet detection
alternative label: Extrasolar planetary system detection
broader: Exoplanet astronomy
narrower: Timing variation methods
narrower: Transit photometry
narrower: Direct imaging
narrower: Polarimetry
narrower: Radial velocity
narrower: Magnetospheric radio emissions
narrower: Astrometric exoplanet detection
contributor: AAS Frey.Katie
narrower: Gravitational microlensing exoplanet detection
modified: 2019-12-13T14:48:36.536Z

Antumbra
type: Concept
broader: Eclipses
contributor: AAS Frey.Katie
definition: That part of the Moon's shadow that extends beyond the umbra. It is similar to the penumbra in that the Sun is only partially blocked by the Moon. From within the antumbra, the Sun appears larger than the Moon which is seen in complete silhouette. An annular eclipse is seen when an observer passes through the antumbra.
modified: 2020-11-03T18:01:53.179Z
editorial note: Definition Provenance
  created: 2020-11-03T18:02:06.075Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T18:02:06.100Z

Exoplanet evolution
type: Concept
broader: Exoplanet astronomy

Exoplanet formation
type: Concept
broader: Exoplanet astronomy

Exoplanet plate tectonics
type: Concept
broader: Exoplanet structure
related: Plate tectonics
modified: 2020-10-26T21:44:30.639Z
contributor: AAS Frey.Katie

Exoplanet rings
type: Concept
broader: Exoplanet structure
related: Planetary rings
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T17:43:27.480Z

Exoplanet surface characteristics
type: Concept
narrower: Exoplanet surface composition
narrower: Exoplanet surface variability
broader: Exoplanet surfaces
contributor: AAS Frey.Katie
modified: 2019-12-02T19:12:55.520Z

Exoplanet tides
type: Concept
broader: Exoplanet dynamics

Exoplanets
type: Concept
alternative label: Extrasolar planets
alternative label: Planets
broader: Exoplanet astronomy
narrower: Mini Neptunes
narrower: Ocean planets
narrower: Pulsar planets
narrower: Super Earths
narrower: Trojan planets
narrower: Carbon planets
narrower: Chthonian planets
narrower: Extrasolar rocky planets
narrower: Free floating planets
narrower: Habitable planets
narrower: Hot Jupiters
narrower: Hot Neptunes
scope note: Specifically planets and related bodies found orbiting stars that are not the Sun.
alternative label: Planets (Extrasolar)
related: Solar system planets
narrower: Extrasolar ice giants
related: Natural satellites (Extrasolar)
narrower: Cold Neptunes
definition: A planet which belongs to a star other than Sun, and therefore does not belong to our solar system; same as exoplanet.
narrower: Extrasolar gaseous planets
modified: 2020-11-09T21:31:25.673Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T21:03:45.737Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:03:45.706Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Exosphere
type: Concept
broader: Earth atmosphere
narrower: Geocorona
contributor: AAS Frey.Katie
definition: The outermost portion of the Earth's atmosphere. Extremely tenuous, it lies above the ionosphere from a height of about 500 km, to the edge of interplanetary space. Since the mean free path is much greater than the atmospheric scale height, the atoms or molecules never collide with each other.
modified: 2020-11-03T21:04:25.421Z
modified: 2020-11-03T21:04:36.503Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:04:36.477Z
  creator: AAS Frey.Katie

A stars
type: Concept
alternative label: A-type stars
alternative label: Class A stars
alternative label: Type A stars
broader: Early-type stars
narrower: Ae stars
narrower: A dwarf stars
narrower: Am stars
narrower: A giant stars
narrower: Ap stars
narrower: A subdwarf stars
narrower: A subgiant stars
narrower: A supergiant stars
related: Stellar classification
alternative label: A type stars
broader: Stellar spectral types
definition: A star whose spectrum shows strong hydrogen Balmer lines accompanied by many faint to moderately strong metallic lines. In contrast to B and O stars, the lines of He I and He II are absent. Their surface temperature ranges from 7,500 to 10,000 K. The main metallic lines seen in A-type stars are those of Fe I and Fe II, Cr I and II, Ti I and II, and account for about two-thirds of all lines. Some famous examples of A star are Sirius, Deneb, Altair, and Vega. Also known as A-type star.
contributor: AAS Frey.Katie
modified: 2020-10-26T18:21:38.213Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:21:50.135Z
  creator: AAS Frey.Katie
modified: 2020-10-26T18:21:50.162Z

Ap stars
type: Concept
alternative label: Peculiar A-type stars
broader: Chemically peculiar stars
broader: A stars
narrower: Manganese stars
narrower: Silicon stars
narrower: Holmium stars
alternative label: Peculiar A stars
alternative label: Ap-type stars
narrower: Rapidly oscillating Ap star
contributor: AAS Frey.Katie
definition: Stars of spectral type A in which lines of ionized metals and rare-earth elements are abnormally enhanced. Such stars have unusually strong magnetic fields, thousands of times stronger than the Sun's typical surface field. Ap stars are generally slow rotators because of magnetic braking.
modified: 2020-11-03T18:02:57.207Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:03:15.954Z
modified: 2020-11-03T18:03:15.990Z

Exozodiacal dust
type: Concept
alternative label: Exo-zodiacal dust
broader: Debris disks
related: Zodiacal cloud

Expanding stellar envelopes
type: Concept
broader: Stellar properties

Expanding universe
type: Concept
broader: Cosmological models
contributor: AAS Frey.Katie
modified: 2020-11-03T21:05:10.682Z
definition: The deduction based on the observational fact that the greater the distance to a galaxy, the greater the redshift in its spectral lines (Doppler effect). The observations strongly indicate that galaxies appear to be moving away from us with speeds proportional to their distance. This is in agreement with the overall expansion of the Universe.
modified: 2020-11-03T21:05:26.674Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:05:26.648Z
  creator: AAS Frey.Katie

Explosive nucleosynthesis
type: Concept
broader: Nucleosynthesis
related: Supernova dynamics
definition: The explosive processes that are believed to occur in supernovae. Explosive carbon burning occurs at a temperature of about 2 x 10^9 degrees and produces the nuclei from neon to silicon. Explosive oxygen burning occurs near 4 x 10^9 degrees and produces nuclei between silicon and calcium in atomic weight. At higher temperatures, still heavier nuclei are produced.
modified: 2020-11-24T17:11:02.138Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T21:06:42.259Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T21:06:42.288Z
contributor: AAS Frey.Katie

Extended radiation sources
type: Concept
broader: Astronomical radiation sources

Extinction
type: Concept
broader: Astronomical optics
narrower: Atmospheric extinction
narrower: Reddening law
narrower: Interstellar extinction
contributor: AAS Frey.Katie
definition: Dimming of light by an intervening medium (the Earth's atmosphere or the interstellar medium). It is usually due to both scattering and absorption.
modified: 2020-11-03T21:08:10.240Z
editorial note: Definition Provenance
  created: 2020-11-03T21:08:22.779Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T21:08:22.814Z

Extragalactic astronomy
type: Concept
broader: Galactic and extragalactic astronomy
narrower: Astrophysical masers
narrower: Extragalactic magnetic fields
narrower: Intergalactic medium
contributor: AAS Frey.Katie
narrower: Circumgalactic medium
narrower: Galaxy environments
definition: The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars.
modified: 2020-11-03T21:08:47.690Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:08:59.747Z
modified: 2020-11-03T21:08:59.771Z

Extragalactic magnetic fields
type: Concept
broader: Extragalactic astronomy

Extragalactic radio sources
type: Concept
broader: Radio sources

Extrasolar gaseous giant planets
type: Concept
broader: Extrasolar gaseous planets
contributor: AAS Frey.Katie Admin
alternative label: Extrasolar gas giants
related: Solar system gas giant planets
modified: 2020-11-09T21:34:48.885Z

Apastron
type: Concept
broader: Apsides
contributor: AAS Frey.Katie
definition: The point at which a binary star is furthest from its companion.
modified: 2020-11-03T18:03:54.448Z
modified: 2020-11-03T18:04:15.145Z
editorial note: Definition Provenance
  created: 2020-11-03T18:04:15.115Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Extrasolar radiation
type: Concept
alternative label: Unidentified sources of radiation outside the Solar System
broader: Astronomical radiation sources

Extrasolar rocky planets
type: Concept
alternative label: Rocky planets
broader: Exoplanets
related: Solar system terrestrial planets
contributor: AAS Frey.Katie Admin
modified: 2020-11-09T21:34:23.822Z

Extreme carbon stars
type: Concept
broader: Giant stars
related: Infrared sources

Extrinsic variable stars
type: Concept
broader: Variable stars
narrower: Eclipsing binary stars
narrower: Ellipsoidal variable stars
definition: A star whose variation in apparent brightness is not due to changes in the star itself but to some external cause, such as eclipsing by a companion.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:15:11.646Z
modified: 2020-11-03T16:15:25.549Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:15:25.517Z

Stellar F corona
type: Concept
alternative label: F components
modified: 2019-11-26T18:05:20.581Z
broader: Stellar coronae
contributor: AAS Frey.Katie
related: Solar F corona
alternative label: Stellar F coronal regions

Interstellar objects
type: Concept
contributor: AAS Frey.Katie Admin
alternative label: Aperiodic comets
alternative label: Interstellar comets
related: Comets
broader: Small Solar System bodies
example: 2I/Borisov
definition: A body other than a star or substellar object not gravitationally bound to a star. Its hyperbolic orbit would indicate an object not bound to the Sun. The first known ISO is 1I/'Oumuamua. ISOs are icy planetesimals that are expected to behave like the long-period comets of the solar system; volatile ices sublimate when the ISO approaches the Sun, developing a coma and a dust tail -- features that should make them bright and therefore easy to spot. The rocky ISOs, on the other hand, only reflect sunlight. As their albedo is expected to be extremely low they become dark (after eons of bombardment by high-energy cosmic rays), they would be extremely faint and hard to detect.
example: 1I/'Oumuamua
scope note: Not to be confused with Exocomets.
related: Exocomets
modified: 2022-06-24T15:14:32.957Z
modified: 2020-12-04T20:47:14.694Z
editorial note: Definition Provenance
  created: 2020-12-04T20:47:14.664Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Fabry-Perot interferometers
type: Concept
alternative label: Etalons
alternative label: FPI
broader: Interferometers

Faint blue stars
type: Concept
broader: Early-type stars

Fanaroff-Riley radio galaxies
type: Concept
alternative label: Fanaroff Riley class I
alternative label: Fanaroff Riley class II
alternative label: Fanaroff-Riley class I
alternative label: Fanaroff-Riley class II
broader: Radio galaxies
contributor: AAS Frey.Katie
definition: Analyzing a sample of 57 radio galaxies from the 3CR catalogue, which were clearly resolved at 1.4 GHz or 5 GHz, Fanaroff & Riley (1974) discovered that the relative positions of regions of high and low surface brightness in the lobes of extragalactic radio sources are correlated with their radio luminosity. They divided the sample into two classes using the ratio RFR of the distance between the regions of highest surface brightness on opposite sides of the central galaxy or quasar, to the total extent of the source up to the lowest brightness contour in the map. Fanaroff-Riley Class I (FR-I) , Fanaroff-Riley Class II (FR-II). The boundary between the two classes is not very sharp, and there is some overlap in the luminosities of sources classified as FR-I or FR-II on the basis of their structures. The physical cause of the FR-I/II dichotomy probably lies in the type of flow in the radio jets.
modified: 2020-11-03T21:09:54.522Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:10:13.531Z
modified: 2020-11-03T21:10:13.562Z

Far infrared interferometry
type: Concept
contributor: AAS Frey.Katie Admin
alternative label: Far-infrared interferometry
broader: Far infrared astronomy
broader: Direct imaging
modified: 2022-06-30T15:04:29.868Z

Far infrared astronomy
narrower: Far infrared interferometry
type: Concept
alternative label: FIR astronomy
alternative label: Far infrared astronomical observations
alternative label: Far ir astronomical observations
alternative label: Far ir astronomy
alternative label: Far-infrared astronomical observations
alternative label: Far-ir astronomical observations
alternative label: Far-ir astronomy
broader: Infrared astronomy
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:38:16.862Z

Aperture synthesis
type: Concept
alternative label: Synthesis imaging
alternative label: Synthetic aperture
broader: Interferometry
contributor: AAS Frey.Katie
modified: 2020-11-03T18:05:27.537Z
definition: The method of combining the signals received by several smaller telescopes distributed over a very large area or baseline to provide the high angular resolution of a much large telescope.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:05:44.265Z
modified: 2020-11-03T18:05:44.291Z

Fast novae
type: Concept
broader: Novae

Few-body systems
type: Concept
broader: N-body problem

Solar fibrils
type: Concept
alternative label: Fibrills
broader: Solar spicules
definition: A linear pattern in the chromosphere of the Sun, as seen through an H-alpha filter, occurring near strong sunspots and plages or in filament channels. They are magnetically confined tubes of hot plasma. Individually, they are about 10,000 km long and last for 10 to 20 minutes.
modified: 2020-11-04T15:19:48.006Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T15:19:59.252Z
editorial note: Definition Provenance
  created: 2020-11-04T15:19:59.227Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Field galaxies
type: Concept
broader: Galaxies
related: Field of view
definition: A galaxy that lies in the direction of a cluster of galaxies, but is not a member of the cluster. Field galaxies are rare, less than about 5% of all galaxies.
contributor: AAS Frey.Katie
modified: 2020-11-03T21:10:54.244Z
editorial note: Definition Provenance
  created: 2020-11-03T21:11:05.080Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T21:11:05.117Z

Field of view
type: Concept
alternative label: FOV
alternative label: Field of vision
alternative label: Fields of view
alternative label: Fields of vision
broader: Astronomical techniques
narrower: Parallel field
narrower: Blank fields
narrower: High latitude field
scope note: At telescope' foci
related: Field galaxies
related: Field stars
contributor: AAS Frey.Katie
definition: The entire angular expanse of the sky viewed by an optical instrument.
modified: 2020-11-03T21:11:37.940Z
modified: 2020-11-03T21:11:51.415Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T21:11:51.384Z

Filamentary nebulae
type: Concept
alternative label: Filamentary nebula
broader: Nebulae
scope note: This concept does not refer specifically to the Filamentary Nebula, a named nebula that is part of the Western Veil (also known as Caldwell 34), consisting of NGC 6960.
contributor: AAS Frey.Katie
related: Interstellar filaments
definition: A type of nebula, generally ionized, consisting of filament-like structures of gas, such as the Veil Nebula (NGC 6960) or the supernova remnant IC 443.
modified: 2020-10-30T19:45:00.276Z
modified: 2020-10-30T19:45:15.882Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:45:15.857Z
  creator: AAS Frey.Katie

Finding charts
type: Concept
broader: Astronomical reference materials
definition: A sketch or image used to recognize objects in the field of view of a telescope.
contributor: AAS Frey.Katie
modified: 2020-10-30T19:45:48.986Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-30T19:46:04.790Z
  creator: AAS Frey.Katie
modified: 2020-10-30T19:46:04.816Z

Finding lists
type: Concept
broader: Astronomical reference materials

Fireballs
type: Concept
broader: Meteors
narrower: Bolides

FK catalog
type: Concept
alternative label: Fundamental Katalog
broader: Catalogs
preferred label: FK catalogue
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:44:20.365Z

Apex
type: Concept
broader: Solar motion
alternative label: Solar apex
contributor: AAS Frey.Katie
definition: The point on the celestial sphere toward which the Sun is apparently moving relative to the local standard of rest. Its position, in the constellation Hercules, is approximately R.A. 18h, Dec. +30°, close to the star Vega. The velocity of this motion is estimated to be about 19.4 km/sec (about 4 AU/year). As a result of this motion, stars seem to be converging toward a point in the opposite direction, the solar antapex.
modified: 2020-11-03T18:06:25.985Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:06:38.881Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:06:38.909Z

Flare stars
type: Concept
broader: Eruptive variable stars
narrower: R Coronae Borealis variable stars
narrower: Red dwarf flare stars
narrower: RS Canum Venaticorum variable stars
narrower: UV Ceti stars
narrower: FU Orionis stars
definition: A member of a class of dwarf stars that undergoes sudden, intense outbursts of light (mean amplitude about 0.5-0.6 mag).
contributor: AAS Frey.Katie Admin
modified: 2020-12-03T20:40:14.356Z
contributor: AAS Frey.Katie
modified: 2020-10-30T19:47:07.290Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:47:07.260Z

Flash spectra
type: Concept
alternative label: Flash spectrum
broader: Solar eclipses
definition: The spectrum of the solar chromosphere obtained during a solar eclipse in the instant before or after totality. In the flash spectrum the usual solar absorption lines are replaced with bright emission lines. This is because in that very short interval only the photosphere is eclipsed by the Moon, and not the chromosphere. The American astronomer Charles A. Young was the first to observe it during the solar eclipse of 1870 (December 22) in Spain.
modified: 2020-11-24T17:25:19.555Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:48:49.278Z
contributor: AAS Frey.Katie
modified: 2020-10-30T19:48:49.317Z

Flash stars
type: Concept
broader: Emission line stars

Flat space
type: Concept
broader: Cosmological parameters

Flux calibration
type: Concept
broader: Spectrophotometry
definition: The calibration of the flux received by a detector in terms of absolute units.
modified: 2020-12-03T20:04:16.397Z
broader: Calibration
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T21:16:10.475Z
  creator: AAS Frey.Katie
modified: 2020-11-03T21:16:10.501Z
contributor: AAS Frey.Katie

Flyby missions
type: Concept
broader: Space probes
definition: A mission in which a trajectory takes a space probe close to a Solar System body (planet, satellite, asteroid, comet) but does not permit it to enter an orbit about the body.
contributor: AAS Frey.Katie
modified: 2020-10-30T19:50:38.255Z
editorial note: Definition Provenance
  created: 2020-10-30T19:50:58.303Z
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-30T19:50:58.333Z

Forbush effect
type: Concept
alternative label: Forbush decrease
broader: Cosmic rays

Fornax dwarf spheroidal galaxy
type: Concept
broader: Dwarf spheroidal galaxies

Free floating planets
type: Concept
alternative label: Free-floating planets
alternative label: Interstellar planets
alternative label: Nomad planets
alternative label: Orphan planets
alternative label: Rogue planets
broader: Exoplanets
related: Gravitational microlensing
related: Gravitational microlensing exoplanet detection
contributor: AAS Frey.Katie
definition: A population of substellar objects which are not bound to stars; they are detected in young star clusters. Their masses, estimated from their fluxes, is several Jupiter masses, lower than those of brown dwarfs. Their formation is not yet explained. Among the envisaged possibilities: 1) These objects form like stars, from protostellar core collapse and subsequent accretion; 2) they form as low-mass members of small groups, and are ejected from the group; 3) they form like planets within circumstellar disks of higher-mass objects, but are ejected either due to internal dynamics or external interactions.
modified: 2020-10-30T19:53:06.007Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T19:53:20.234Z
modified: 2020-10-30T19:53:20.259Z

Aphelion
type: Concept
broader: Apsides
contributor: AAS Frey.Katie
definition: The point in the orbit of a planet, or other object in the solar system, which is furthest from the Sun.
modified: 2020-11-03T18:07:12.712Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:07:26.573Z
modified: 2020-11-03T18:07:26.611Z

Friedmann-Robertson-Walker metric
type: Concept
broader: Spacetime metric

Friedmann universe
type: Concept
broader: Cosmological models

Frozen in elements
type: Concept
alternative label: Frozen-in elements
broader: Chemical abundances

Fundamental parameters of stars
type: Concept
alternative label: Fundamental properties of stars
broader: Astrometry

G stars
type: Concept
alternative label: Class G stars
alternative label: G-type stars
broader: Intermediate-type stars
narrower: G dwarf stars
narrower: G giant stars
narrower: G subdwarf stars
narrower: G subgiant stars
narrower: G supergiant stars
related: Stellar classification
broader: Stellar spectral types
definition: A member of a class of stars to which the Sun belongs. The G-type stars on the main sequence have surface temperatures of 5,300-6,000 K and therefore appear yellow in color. G type giant stars (such as Capella) are almost 100-500 K colder than the corresponding main sequence stars. G type supergiants have temperatures of 4,500-5,500 K. The spectrum of early type G stars, such as the Sun (G2), is dominated by ionized lines of calcium (H and K lines, mainly) and neutral metals. In later type G stars the molecular bands of CH molecules and CN molecules become visible. The main sequence and giant stars have masses of ~ 1 solar mass, while the supergiants are of ~ 10 solar masses. The luminosities of G-type giants are almost 30-60 times greater than that of the Sun, whereas the supergiants are 10,000-30,000 times more luminous.
modified: 2020-10-30T19:55:49.273Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-10-30T19:56:09.430Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-30T19:56:09.460Z

Apocenter
type: Concept
alternative label: Apapsis
alternative label: Apoapsis
preferred label: Apocentre
broader: Apsides
definition: The point on an elliptic orbit at the greatest distance from the principal focus or center of attraction.
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:24:47.291Z
modified: 2020-11-03T18:08:10.230Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:08:10.202Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie

Galactic and extragalactic astronomy
type: Concept
narrower: Extragalactic astronomy
narrower: Galaxies
narrower: Galaxy clusters
narrower: Galaxy groups
narrower: Galaxy physics
top concept of: The Unified Astronomy Thesaurus
contributor: AAS Frey.Katie
modified: 2020-10-21T21:19:40.609Z

Galactic anticenter
type: Concept
broader: Milky Way Galaxy physics
related: Galaxy anticenters
definition: The point in the Galactic plane that lies directly opposite the Galactic center. It lies in the constellation Auriga at approximately R.A. 05h 46m, Dec. +28° 56'.
modified: 2021-08-24T15:26:02.978Z
preferred label: Galactic anticentre
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T21:18:44.860Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie
modified: 2020-11-03T21:18:44.897Z

Galactic center
type: Concept
alternative label: Center of the Milky Way
alternative label: Galactic Centre
alternative label: Milky Way Galaxy nucleus
alternative label: Milky Way center
broader: Milky Way Galaxy physics
related: Oort constants
definition: The rotational center of the Milky Way galaxy located in the direction of the Sagittarius constellation at a distance of 7.62 ± 0.32 kpc. Its equatorial coordinates (J2000 epoch) are: R.A. 17h45m40.04s, Dec. -29° 00' 28.1''. The Sun orbits around the Galactic center once every 200 million years at a speed of 220 km per second. It is believed that there is a supermassive black hole at the Galactic center.
preferred label: Galactic centre
contributor: AAS Frey.Katie Admin
modified: 2021-08-24T15:26:26.383Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T14:51:42.463Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie
modified: 2020-11-09T14:51:42.496Z

Galactic coordinate system
type: Concept
broader: Astronomical coordinate systems
narrower: Quadrants
narrower: Galactic latitude
narrower: Galactic longitude
narrower: Galactic poles

Galactic cosmic rays
type: Concept
broader: Cosmic rays

Galactic latitude
type: Concept
broader: Galactic coordinate system
contributor: AAS Frey.Katie
definition: In the Galactic coordinate system, the angle between the line of sight to an object and the Galactic equator. Galactic latitude ranges from +90 degrees to -90 degrees.
modified: 2020-11-09T14:54:35.999Z
modified: 2020-11-09T14:54:48.238Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T14:54:48.204Z
  creator: AAS Frey.Katie

Galactic longitude
type: Concept
broader: Galactic coordinate system
contributor: AAS Frey.Katie
definition: In the Galactic coordinate system, the angle between the Galactic Center and the projection of the object on the Galactic plane. Galactic longitude ranges from 0 degrees to 360 degrees.
modified: 2020-11-09T14:55:21.112Z
editorial note: Definition Provenance
  created: 2020-11-09T14:55:32.445Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T14:55:32.470Z

Apogee
type: Concept
broader: Apsides
contributor: AAS Frey.Katie
modified: 2020-11-03T18:08:40.752Z
definition: The point in the orbit of the moon or an artificial satellite that is farthest from the terrestrial center and at which the body's velocity is at a minimum.
modified: 2020-11-03T18:08:55.588Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:08:55.552Z

Galactic poles
type: Concept
broader: Galactic coordinate system
narrower: North galactic pole
narrower: South galactic pole

Galactic radio sources
type: Concept
broader: Radio sources
scope note: Radio sources which pertain to the Milky Way galaxy

Galactic winds
type: Concept
alternative label: Galactic winds in the Milky Way
alternative label: Milky Way Galaxy winds
alternative label: Milky Way galactic winds
broader: Milky Way Galaxy physics
related: Galaxy winds
scope note: Includes galactic winds in the Milky Way.
contributor: AAS Frey.Katie
modified: 2020-10-30T20:00:22.243Z

Galaxies
contributor: AAS Frey.Katie Admin
narrower: Quenched galaxies
type: Concept
broader: Galactic and extragalactic astronomy
narrower: Primordial galaxies
narrower: Protogalaxies
narrower: Quasar-galaxy pairs
narrower: Radio jets
narrower: Starburst galaxies
narrower: Active galaxies
narrower: Compact galaxies
narrower: Companion galaxies
narrower: Disk galaxies
narrower: Double galaxies
narrower: Dwarf galaxies
narrower: Early-type galaxies
narrower: Elliptical galaxies
narrower: Emission line galaxies
narrower: Field galaxies
narrower: Giant galaxies
narrower: High-redshift galaxies
narrower: High-velocity stars
narrower: Infrared excess galaxies
narrower: Interacting galaxies
narrower: Irregular galaxies
narrower: Late-type galaxies
narrower: Low surface brightness galaxies
narrower: Lyman-alpha galaxies
narrower: Lyman-break galaxies
related: Galaxy classification systems
related: Galaxy photometry
related: Galaxy spectroscopy
definition: Generally, a large body of gas, dust, and stars held together by their mutual gravitational attraction and ranging in mass from about 10^6 to 10^13 M_sun. If a galaxy also contains dark matter its mass will be much larger. Galaxies are grouped into three main categories: spiral galaxies, elliptical galaxies, and irregular galaxies.
modified: 2020-11-02T16:14:21.035Z
narrower: Post-starburst galaxies
editorial note: Definition Provenance
  created: 2020-11-02T16:14:38.856Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-02T16:14:38.887Z

Galaxy abundances
type: Concept
broader: Chemical abundances
broader: Galaxy physics
related: Galactic abundances
alternative label: Galaxy chemical composition
broader: Galaxy properties
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:03:19.964Z

Galaxy accretion
type: Concept
broader: Accretion
broader: Galaxy processes
narrower: Galaxy infall
related: Galaxy accretion disks

Galaxy ages
type: Concept
alternative label: Ages of galaxies
alternative label: Galactic age
alternative label: Galactic ages
broader: Galaxy properties

Galaxy anticenters
type: Concept
alternative label: Anticenter
broader: Galaxy kinematics
related: Galactic anticenter
preferred label: Galaxy anticentres
modified: 2021-08-24T15:41:21.177Z
contributor: AAS Frey.Katie Admin

Galaxy bulges
type: Concept
related: Galactic bulge
contributor: AAS Frey.Katie
broader: Galaxy structure
modified: 2020-10-30T20:08:33.835Z
definition: A spheroidal region at the center of a spiral galaxy which mostly contains old stars. Galactic bulges are generally classified into two types: classical bulges and pseudo-bulges.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-30T20:09:00.619Z
modified: 2020-10-30T20:09:00.653Z

Apollo group
type: Concept
alternative label: Apollo asteroids
broader: Near-Earth objects
definition: A member of a class of near-Earth asteroids (NEAs) that have orbital semi-major axes greater than that of the Earth (> 1 astronomical unit) but perihelion distances less than the Earth's aphelion distance (less than 1.017 AU); thus, they cross the Earth's orbit when near the perihelia of their orbits. They are named for the prototype Apollo.
modified: 2020-10-26T18:43:15.170Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-10-26T18:43:26.280Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-10-26T18:43:26.311Z

Galaxy chemical evolution
type: Concept
broader: Galaxy evolution
narrower: Chemical enrichment

Galaxy circumnuclear disk
type: Concept
alternative label: Circumnuclear matter
alternative label: Galactic circumnuclear matter
broader: Galaxy nuclei

Galaxy classification systems
type: Concept
alternative label: Classification of galaxies
alternative label: Galactic morphology
alternative label: Galaxy classification
alternative label: Galaxy morphological classification
alternative label: Galaxy morphology
broader: Classification systems
narrower: DDO classification
narrower: De Vaucouleurs Sandage classification
narrower: Hubble classification scheme
related: Elliptical galaxies
related: Galaxies
related: Galaxy physics

Galaxy cluster counts
type: Concept
alternative label: Galaxy cluster counting
broader: Cosmic web
broader: Galaxy physics

Galaxy clusters
type: Concept
alternative label: Cluster of galaxies
alternative label: Galaxy clustering
broader: Galactic and extragalactic astronomy
narrower: Perseus Cluster
narrower: Bautz-Morgan type
narrower: Superclusters
narrower: Virgo Cluster
narrower: Coma Cluster
narrower: Intracluster medium
narrower: Abell clusters
narrower: Rich galaxy clusters
narrower: Poor galaxy clusters
narrower: High-redshift galaxy clusters
alternative label: Groups of galaxies
definition: An aggregation of galaxies, made up of a few to a few thousand members, which may or may not be held together by its own gravity.
modified: 2020-11-02T16:18:47.571Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:19:02.162Z
editorial note: Definition Provenance
  created: 2020-11-02T16:19:02.129Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Galaxy collisions
type: Concept
alternative label: Galactic collisions
broader: Interacting galaxies

Galaxy colors
type: Concept
alternative label: Galactic colors
alternative label: Galactic colours
broader: Galaxy properties
narrower: Red sequence galaxies
narrower: Blue cloud galaxies
narrower: Green valley galaxies
contributor: AAS Frey.Katie Admin
preferred label: Galaxy colours
modified: 2021-08-20T13:42:57.543Z

Galaxy counts
type: Concept
broader: Surveys

Apparent magnitude
type: Concept
alternative label: Visual magnitude
broader: Magnitude
narrower: Period determination
narrower: Photoelectric magnitude
narrower: Photographic magnitude
narrower: Photovisual magnitude
narrower: Pogson scale
narrower: Two-color diagrams
narrower: Variable star period change
narrower: Limiting magnitude
contributor: AAS Frey.Katie
modified: 2020-11-03T18:09:41.442Z
definition: A measure of a star's observed brightness (opposed to absolute magnitude); symbol m. It depends on the star's intrinsic brightness, its distance from the observer, and the amount of interstellar absorption. The brightest star Sirius has an apparent magnitude of -1.46, while the weakest stars visible with the naked eye in the most favorable observation conditions have magnitudes of about +6.5. The stars of magnitudes less than +23 are measured by professional observatories, whereas those of magnitudes less than +30 by a telescope such as the Hubble Space Telescope.
modified: 2020-11-03T18:09:53.877Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:09:53.850Z

Galaxy distances
type: Concept
broader: Galaxy physics
narrower: Holmberg radius
narrower: Hubble radius

Galaxy encounters
type: Concept
broader: Galaxy physics

Galaxy equators
type: Concept
alternative label: Galactic equators
broader: Galaxy kinematics

Galaxy formation
type: Concept
broader: Galaxy physics
narrower: Stellar feedback
narrower: Density wave model
contributor: AAS Frey.Katie
related: Milky Way formation
definition: The study dealing with the processes that gave rise to galaxies in a remarkably early Universe.
modified: 2020-11-09T14:58:24.780Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T14:58:35.579Z
modified: 2020-11-09T14:58:35.610Z

Galaxy fountains
type: Concept
broader: Galaxy processes
broader: Galaxy properties
editorial note: Galactic fountains are considered as both structural features and dynamic processes.
related: Milky Way Galaxy fountains

Galaxy groups
type: Concept
broader: Galactic and extragalactic astronomy
narrower: Hickson compact group
narrower: Local Group
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:46:09.853Z

Galaxy infall
type: Concept
broader: Galaxy accretion

Apparent position
type: Concept
alternative label: Apparent places
broader: Astronomical location
modified: 2020-11-03T18:10:39.462Z
contributor: AAS Frey.Katie
definition: A position given by the coordinates calculated for a star, if it were seen from the Earth's center, relative to the real equator and the real equinox, at a certain date. It includes the displacements from one heliocentric direction, given in a stellar catalogue, due to precession, nutation, aberration, proper motions, annual parallax, and light gravitational deviation.
modified: 2020-11-03T18:10:57.040Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-03T18:10:57.001Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Galaxy interactions
type: Concept
alternative label: Galactic interactions
broader: Galaxy physics
narrower: Galaxy mergers

Galaxy jets
type: Concept
broader: Galaxy properties
broader: Jets
editorial note: Galactic jets are considered as both structural features and dynamic processes.

Galaxy kinematics
type: Concept
broader: Galaxy processes
narrower: Galaxy anticenters
narrower: Galaxy equators
narrower: Galaxy planes
narrower: Galaxy rotation

Galaxy luminosities
type: Concept
alternative label: Galaxy luminosity
broader: Galaxy properties

Galaxy mass distribution
type: Concept
broader: Galaxy masses
narrower: Navarro-Frenk-White profile

Galaxy mergers
type: Concept
broader: Galaxy interactions
broader: Interacting galaxies

Apparent superluminal motion
type: Concept
alternative label: Apparent FTL
alternative label: Effective FTL
alternative label: Fast-than-light
alternative label: Faster than light
alternative label: Superluminal motion
broader: Celestial mechanics

Galaxy pairs
type: Concept
alternative label: Galactic pairs
alternative label: Pair of galaxies
broader: Interacting galaxies

Galaxy photometry
type: Concept
broader: Photometry
contributor: AAS Frey.Katie
related: Galaxies
modified: 2020-10-21T21:19:52.626Z

Galaxy physics
type: Concept
alternative label: Galactic physics
broader: Galactic and extragalactic astronomy
narrower: Milky Way Galaxy physics
narrower: Stellar kinematics
narrower: Galaxy accretion disks
narrower: Galaxy abundances
narrower: Galaxy cluster counts
narrower: Galaxy distances
narrower: Galaxy dynamics
narrower: Galaxy encounters
narrower: Galaxy formation
narrower: Galaxy interactions
narrower: Galaxy processes
narrower: Galaxy properties
narrower: Galaxy spurs
narrower: Galaxy structure
related: Galaxy classification systems
narrower: Voids
contributor: AAS Frey.Katie Admin
modified: 2020-11-25T18:51:48.353Z

Galaxy planes
type: Concept
broader: Galaxy kinematics

Galaxy processes
type: Concept
alternative label: Galactic motion
alternative label: Galactic processes
broader: Galaxy physics
narrower: Galaxy accretion
narrower: Galaxy dynamics
narrower: Galaxy evolution
narrower: Galaxy fountains
narrower: Galaxy kinematics
narrower: Galaxy winds

Galaxy properties
type: Concept
alternative label: Galactic properties
broader: Galaxy physics
narrower: Galaxy ages
narrower: Galaxy colors
narrower: Galaxy fountains
narrower: Galaxy jets
narrower: Galaxy luminosities
narrower: Galaxy magnetic fields
narrower: Galaxy magnitudes
narrower: Galaxy masses
narrower: Galaxy radial velocities
narrower: Galaxy radii
narrower: Galaxy stellar content
narrower: Galaxy abundances
narrower: Scaling relations
contributor: AAS Frey.Katie Admin
modified: 2020-12-03T21:36:57.018Z

Galaxy radial velocities
type: Concept
broader: Galaxy properties

Galaxy radii
type: Concept
alternative label: Galactic radius
broader: Galaxy properties

Galaxy rotation curves
type: Concept
alternative label: Rotation curves
broader: Galaxy rotation

Apsidal motion
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
definition: Rotation of the line of apsides in the plane of the orbit in the same direction as the revolution of the secondary body. The major axis of the Earth's orbit rotates by 11.6 arcseconds per year.
modified: 2020-11-03T18:14:17.413Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:14:29.368Z
modified: 2020-11-03T18:14:29.398Z

Galaxy spurs
type: Concept
broader: Galaxy physics

Galaxy stellar content
type: Concept
alternative label: Galactic stellar populations
broader: Galaxy properties

Galaxy structure
type: Concept
alternative label: Galactic structure
broader: Galaxy physics
narrower: Radio cores
narrower: Spiral pitch angle
narrower: Galaxy disks
narrower: Galaxy bulges
narrower: Galaxy stellar halos
narrower: Galaxy nuclei
narrower: Spiral arms
narrower: Circumgalactic medium
narrower: Galaxy dark matter halos
narrower: Galaxy spheroids
narrower: Galaxy tails
narrower: Stellar streams
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:57:15.419Z

Galaxy tides
type: Concept
alternative label: Galactic tidal interactions
alternative label: Galactic tides
alternative label: Galaxial tidal interactions
alternative label: Galaxial tides
alternative label: Galaxy tidal interactions
broader: Interacting galaxies

Galaxy triplets
type: Concept
alternative label: Galactic triplets
alternative label: Galaxy triples
broader: Interacting galaxies

Galaxy winds
type: Concept
broader: Galaxy processes
related: Galactic winds
definition: An outflow of hot gas, analogous to the solar wind, from a galaxy that has recently undergone a high burst of star formation or has an active galactic nucleus. Galaxy winds are streams of high speed charged particles blowing out of galaxies with speeds of 300 to 3,000 km s^-1. In the case of starbursts, galactic winds are powered by stellar winds driven by massive stars and supernova explosions. Galaxy winds contain a mixture of extremely hot metal-enriched supernova ejecta and cooler entrained gas and dust. Outflowing material has been observed at great distances from galaxies (10 to 100 kpc). In some cases they escape the galaxy potential well and pollute the intergalactic medium with heavy elements. A prominent example is the superwind of the starburst galaxy M82.
modified: 2020-10-30T20:00:55.252Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-10-30T20:01:10.253Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-30T20:01:10.282Z

Galilean satellites
type: Concept
alternative label: Galilean moons
broader: Jovian satellites
definition: The four largest and brightest satellites of Jupiter, that is: Io, Europa, Ganymede, and Callisto.
contributor: AAS Frey.Katie Admin
narrower: Ganymede
narrower: Europa
narrower: Io
modified: 2022-06-15T15:31:01.075Z
narrower: Callisto
modified: 2020-11-09T15:03:39.650Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T15:03:39.619Z
contributor: AAS Frey.Katie

Gamma-ray astronomy
type: Concept
alternative label: Gamma astronomy
alternative label: Gamma ray astronomical observations
alternative label: Gamma ray astronomy
alternative label: Gamma-ray astronomical observations
alternative label: γ-ray astronomy
broader: Astronomical methods
related: Gamma-ray sources
contributor: AAS Frey.Katie
definition: The study of gamma rays from extraterrestrial sources, especially gamma-ray bursts. Gamma-rays are an electromagnetic wave with a typical wavelength less than 10-2Å (10-12 m), corresponding to frequencies above 1019 Hz and photon energies above 100 keV.
modified: 2024-06-20T13:15:01.829Z
editorial note: Definition Provenance
  created: 2024-06-20T13:16:46.551Z
  creator: AAS Frey.Katie
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2024-06-20T13:16:50.636Z

Gamma-ray bursts
alternative label: γ-ray bursts
type: Concept
alternative label: Cosmic gamma ray burst
alternative label: Cosmic gamma-ray burst
alternative label: GRB
alternative label: Gamma ray burst
alternative label: Gamma ray bursts
broader: Gamma-ray sources
broader: Burst astrophysics
related: Gamma-ray bursters
alternative label: Gamma-ray burst
related: Gamma-ray transient sources
contributor: AAS Frey.Katie Admin
definition: An intense discharge of gamma rays, which range in duration from tenth of a second to tens of seconds and occur from sources widely distributed over the sky. The radio wave afterglow from the burst can last more than a year, making long-term observations of the sources possible. The favored hypothesis is that they are produced by a relativistic jet created by the merger of two compact objects (specifically two neutron stars or a neutron star and a black hole). Mergers of this kind are also expected to create significant quantities of neutron-rich radioactive species, whose decay should result in a faint transient, known as a kilonova, in the days following the burst. Indeed, it is speculated that this mechanism may be the predominant source of stable r-process elements in the Universe. Recent calculations suggest that much of the kilonova energy should appear in the near-infrared spectral range, because of the high optical opacity created by these heavy r-process elements.
modified: 2020-11-02T16:24:52.305Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:25:10.150Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-02T16:25:10.182Z

Apsides
type: Concept
alternative label: Apse
broader: Orbital elements
narrower: Periapsis
narrower: Periastron
narrower: Perigee
narrower: Perihelion
narrower: Apastron
narrower: Aphelion
narrower: Apocenter
narrower: Apogee
contributor: AAS Frey.Katie
alternative label: Apsis
definition: The point of greatest or least distance of the orbit of a celestial body from a center of attraction. The closest point is the periapsis, the further point the apoapsis.
modified: 2020-10-26T18:44:18.583Z
modified: 2020-10-26T18:44:31.717Z
editorial note: Definition Provenance
  created: 2020-10-26T18:44:31.680Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Gamma-ray detectors
type: Concept
broader: Astronomical detectors

Gamma-ray observatories
type: Concept
alternative label: Gamma ray observatories
broader: Observatories
broader: Space observatories

Gamma-ray sources
type: Concept
alternative label: Gamma objects
alternative label: Gamma sources
alternative label: Gamma-ray objects
broader: Gamma-rays
broader: Astronomical radiation sources
narrower: Soft gamma-ray repeaters
alternative label: Gamma-ray radiation sources
alternative label: Gamma ray sources
narrower: Gamma-ray bursts
narrower: Gamma-ray transient sources
related: Gamma-ray astronomy
related: Gamma-ray bursters
definition: An astronomical object that emits gamma rays.
modified: 2020-11-02T16:26:21.656Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-02T16:26:36.170Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-02T16:26:36.199Z

Gamma-ray telescopes
type: Concept
alternative label: Gamma telescopes
broader: Space telescopes
alternative label: γ-ray telescopes
alternative label: Gamma ray telescopes
broader: Telescopes
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:51:45.882Z

Gamma-rays
type: Concept
alternative label: Gamma radiation
broader: Particle astrophysics
narrower: Gamma-ray lines
narrower: Gamma-ray sources
alternative label: Gamma rays
contributor: AAS Frey.Katie Admin
definition: An electromagnetic wave with a typical wavelength less than 10^-2 Å (10^-12 m), corresponding to frequencies above 10^19 Hz and photon energies above 100 keV.
modified: 2020-11-02T16:23:30.859Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:23:49.114Z
modified: 2020-11-02T16:23:49.146Z

Gas-to-dust ratio
type: Concept
alternative label: Dust to gas ratio
alternative label: Dust-to-gas ratio
alternative label: Gas to dust ratio
broader: Astronomical models
contributor: AAS Frey.Katie
definition: The mass ratio of gas to dust. It amounts to approximately 100 in the interstellar medium, but may vary in molecular clouds and circumstellar disks due to dust grain evaporation, dust settling, condensation of gas, etc. The gas-to-dust ratio depends on the metallicity. It is larger in galaxies with lower metallicity.
modified: 2020-11-09T15:08:18.274Z
editorial note: Definition Provenance
  created: 2020-11-09T15:08:28.773Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T15:08:28.806Z

Gaseous nebulae
type: Concept
alternative label: Gaseous nebula
broader: Nebulae
related: Emission nebulae
definition: An H II region, a planetary nebula, or a supernova remnant.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:27:22.943Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:27:38.116Z
modified: 2020-11-02T16:27:38.141Z

Archaeoastronomy
type: Concept
alternative label: Ancient astronomy
alternative label: Archeoastronomy
alternative label: Astroarchaeology
alternative label: Astroarcheology
narrower: Megalithic astronomy
related: Early astronomical instruments
definition: The study that deals with the astronomical knowledge of prehistoric peoples (season events, calendars, observing sites, astronomical alignments) and its influence on their cultures and societies (mythologies, religions, life). Archaeoastronomy covers the intersection between astronomy and archaeology.
broader: Cultural astronomy
contributor: AAS Frey.Katie Admin
modified: 2022-06-24T17:23:45.950Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:17:53.434Z
contributor: AAS Frey.Katie
modified: 2020-11-03T18:17:53.459Z

Gegenschein
type: Concept
alternative label: Counterglow
broader: Night sky brightness
contributor: AAS Frey.Katie
modified: 2020-11-09T15:09:44.331Z
definition: A faint glow of light in the night sky seen exactly opposite the Sun. The gegenschein is sunlight back-scattered off millimeter-sized dust particles along the ecliptic. In comparison with zodiacal light (forward-scattered sunlight), which is triangular in shape and found near the horizon, the gegenschein is roughly circular.
modified: 2020-11-09T15:09:56.074Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:09:56.044Z

General relativity
type: Concept
alternative label: General theory of relativity
broader: Relativity
broader: Gravitation
narrower: Spacetime metric
narrower: Einstein field equations
narrower: Evolution equation
narrower: Geodesics
narrower: Gravitational collapse
narrower: Gravitational lensing
narrower: Gravitational singularities
narrower: Gravitational waves
contributor: AAS Frey.Katie
definition: The theory of gravitation developed by Albert Einstein (1916) that describes the gravitation as the space-time curvature caused by the presence of matter or energy. Mass creates a gravitational field which distorts the space and changes the flow of time. In other words, mass causes a deviation of the metric of space-time continuum from that of the 'flat' space-time structure described by the Euclidean geometry and treated in special relativity. General relativity developed from the principle of equivalence between gravitational and inertial forces. According to general relativity, photons follow a curved path in a gravitational field. This prediction was confirmed by the measurements of star positions near the solar limb during the total eclipse of 1919. The same effect is seen in the delay of radio signals coming from distant space probes when grazing the Sun's surface. Moreover, the space curvature caused by the Sun makes the perihelion of Mercury's orbit advance by 43'' per century more than that predicted by Newton's theory of gravitation. The perihelion advance can reach several degrees per year for binary pulsar orbits. Another effect predicted by general relativity is the gravitational reddening. This effect is verified in the redshift of spectral lines in the solar spectrum and, even more obviously, in white dwarfs. Other predictions of the theory include gravitational lensing, gravitational waves, and the invariance of Newton's gravitational constant.
modified: 2020-11-09T15:10:47.707Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:10:59.149Z
modified: 2020-11-09T15:10:59.183Z

Geneva photometry
type: Concept
alternative label: Ubvgri photometry
broader: Medium band photometry
alternative label: Geneva photometric system
contributor: AAS Frey.Katie
modified: 2020-10-21T18:31:08.526Z

Geocentric orbit
type: Concept
broader: Orbital motion

Geocorona
type: Concept
broader: Exosphere
contributor: AAS Frey.Katie
definition: The outermost part of Earth's atmosphere, a tenuous halo of hydrogen and some helium extending out to perhaps 15 Earth radii, which emits Lyman-alpha radiation when it is bombarded by sunlight.
modified: 2020-11-09T15:11:29.268Z
modified: 2020-11-09T15:11:40.554Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T15:11:40.511Z

Geodesics
type: Concept
broader: General relativity
narrower: Penrose limit
narrower: Gravitational deflection
contributor: AAS Frey.Katie
definition: The shortest distance between two points in space (or space-time). A geodesic on a sphere is an arc of a great circle. In the theory of general relativity, freely falling bodies follow geodesic paths in space-time.
modified: 2020-11-09T15:12:12.645Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-09T15:12:25.286Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T15:12:25.319Z

Geomagnetic fields
type: Concept
broader: Magnetic fields

Geostationary satellites
type: Concept
broader: Geosynchronous satellites
definition: A satellite that orbits in the plane of the Earth's equator and 35,880 km above it, at which distance the satellite's period of rotation matches the Earth's and the satellite always remains fixed in the same spot over the Earth.
modified: 2020-11-02T16:32:21.931Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:32:39.422Z
modified: 2020-11-02T16:32:39.445Z

Geosynchronous satellites
type: Concept
broader: Artificial satellites
narrower: Geostationary satellites
definition: A satellite that has a circular orbit around the Earth identical to a geostationary orbit except that the satellite's orbit does not necessarily lie in the Earth's equatorial plane.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:33:10.759Z
modified: 2020-11-02T16:33:28.367Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:33:28.338Z

Argument of perigee
type: Concept
broader: Orbital elements
contributor: AAS Frey.Katie
definition: The angular distance between the ascending node of an object orbiting the Earth and its perigee, measured from the Earth.
modified: 2020-11-03T18:18:23.248Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:18:35.962Z
modified: 2020-11-03T18:18:35.994Z

Giant branch
type: Concept
broader: Hertzsprung Russell diagram
narrower: Red giant branch
alternative label: Giant branches
related: Giant stars
contributor: AAS Frey.Katie
definition: A conspicuous family of stars in the Hertzsprung-Russell diagram composed of red, evolved stars with large sizes.
modified: 2020-11-09T15:45:36.834Z
modified: 2020-11-09T15:45:47.668Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-09T15:45:47.635Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Giant elliptical galaxies
type: Concept
alternative label: Giant ellipticals
broader: Elliptical galaxies
broader: Giant galaxies

Giant galaxies
type: Concept
broader: Galaxies
narrower: Brightest cluster galaxies
narrower: cD galaxies
narrower: Giant elliptical galaxies

Giant molecular clouds
type: Concept
broader: Molecular clouds
alternative label: GMC
contributor: AAS Frey.Katie Admin
definition: A massive complex of interstellar gas and dust, consisting mostly of molecular hydrogen, that typically stretches over 150 light-years and contains several hundred thousand solar masses. Giant molecular clouds are the principal sites of star formation.
modified: 2020-11-05T15:55:01.698Z
modified: 2020-11-05T15:55:14.609Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-05T15:55:14.579Z

Giant radio galaxies
type: Concept
broader: Radio galaxies

Giant stars
type: Concept
alternative label: CS stars
broader: Evolved stars
narrower: O giant stars
narrower: OH/IR stars
narrower: Chemically peculiar giant stars
narrower: B giant stars
narrower: R stars
narrower: Red giant stars
narrower: S stars
narrower: Weak G band stars
narrower: CH stars
narrower: CN stars
narrower: A giant stars
narrower: Extreme carbon stars
narrower: F giant stars
narrower: G giant stars
narrower: Late-type giant stars
narrower: Lb variable stars
related: Giant branch
contributor: AAS Frey.Katie Admin
definition: A high-luminosity star that has evolved off the main sequence and lies above the main sequence on the Hertzsprung-Russell diagram. A member of the giant branch.
modified: 2020-11-02T16:34:45.070Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:35:01.774Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-02T16:35:01.804Z

Globular star clusters
type: Concept
alternative label: Globular clusters
broader: Star clusters
definition: A spherical aggregate of stars made up of thousands to a few million stars which is an orbiting satellite of a galaxy. There are over 150 globular clusters orbiting our galaxy. Globular clusters are gravitationally bound systems, highly concentrated to the center (up to a few 10^3 stars per cubic light-years), with a volume ranging from a few dozen up to more than 300 light-years in diameter. They are generally old and metal-poor and are among the first objects to be formed in a galaxy. There is also strong evidence that they form in major galaxy interactions and mergers. The stars in a globular cluster are thought to have a common origin and thus a single age and chemical abundance; with some exceptions such as Omega Centauri and NGC 2808, which exhibit multiple populations. The presence of various sub-populations within a globular cluster is interpreted as indicating distinct epochs of mass accretion and/or major star formation. The Milky Way hosts about 200 globular clusters. They are spherically distributed about the Galactic Center up to a radius of 350 light-years, with a maximum concentration toward the Galactic center. All but the smallest dwarf galaxies possess globular clusters. Some galaxies, e.g. M87, contain several thousands of them. There are, however, important differences. While all the globular clusters in our Galaxy and in M31 are old (ages of about 10 billion years, at least), there are galaxies, such as the two Magellanic Clouds and M33, that host much younger globular clusters (ages of a few billion years, or less).
modified: 2020-11-04T16:35:33.288Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T16:35:45.814Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T16:35:45.849Z

Gödel universe
type: Concept
alternative label: Constructible universe
alternative label: Godel universe
alternative label: Goedel universe
broader: Cosmological models

Gould Belt
type: Concept
alternative label: Gould's Belt
alternative label: Goulds belt
broader: Milky Way Galaxy physics

Argument of perihelion
type: Concept
broader: Orbital elements
contributor: AAS Frey.Katie
definition: The angular distance between the ascending node of an object orbiting the Sun and its perihelion. Argument of perihelion is measured in the orbital plane with respect to the Sun and in the direction of motion. It is one of the orbital elements and usually shown with the symbol ω.
modified: 2020-11-03T18:19:14.364Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:19:30.494Z
modified: 2020-11-03T18:19:30.524Z

Gravastars
type: Concept
alternative label: Gravitational condensate stars
broader: Quantum gravity

Gravitation
type: Concept
alternative label: Gravitational force
alternative label: Gravity
broader: Astrophysical processes
narrower: Newtonian gravitation
narrower: Non-standard theories of gravity
narrower: Celestial mechanics
narrower: General relativity
related: Relativity
related: Stellar physics
contributor: AAS Frey.Katie
definition: The universal phenomenon of attraction between material bodies.
modified: 2020-11-09T15:48:08.854Z
modified: 2020-11-09T15:48:19.414Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T15:48:19.380Z

Gravitational collapse
type: Concept
broader: General relativity
narrower: Chandrasekhar limit
contributor: AAS Frey.Katie
narrower: Jeans mass
narrower: Schonberg-Chandrasekhar limit
definition: Collapse of a mass of material as a result of the mutual gravitational attraction of all its constituents.
modified: 2020-11-09T15:49:16.479Z
editorial note: Definition Provenance
  created: 2020-11-09T15:49:26.224Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T15:49:26.255Z

Gravitational deflection
type: Concept
broader: Geodesics

Gravitational disruption
type: Concept
broader: Newtonian gravitation
narrower: Tidal disruption

Gravitational energy
type: Concept
broader: Newtonian gravitation
contributor: AAS Frey.Katie
definition: The energy that an object possesses because of its position in a gravitational field, especially an object near the surface of the Earth where the gravitational acceleration can be assumed to be constant, at about 9.8 m s^-2.
modified: 2020-11-09T15:50:02.857Z
modified: 2020-11-09T15:50:14.763Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:50:14.734Z

Gravitational equilibrium
type: Concept
broader: Newtonian gravitation
contributor: AAS Frey.Katie
definition: The condition in a celestial body when gravitational forces acting on each point are balanced by some outward pressure, such as radiation pressure or electron degeneracy pressure, so that no vertical motion results.
modified: 2020-11-09T15:50:44.961Z
modified: 2020-11-09T15:50:56.880Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T15:50:56.847Z

Gravitational fields
type: Concept
alternative label: Gravity field
broader: Newtonian gravitation
definition: The region of space in which gravitational attraction exists.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T15:55:16.775Z
editorial note: Definition Provenance
  created: 2020-11-02T15:55:28.352Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-02T15:55:28.380Z

Gravitational instability
type: Concept
broader: Newtonian gravitation
contributor: AAS Frey.Katie
definition: The process by which fluctuations in an infinite medium of size greater than a certain length scale (the Jeans length) grow by self-gravitation.
modified: 2020-11-09T15:53:21.483Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:53:31.730Z
modified: 2020-11-09T15:53:31.766Z

Gravitational interaction
type: Concept
broader: Newtonian gravitation
narrower: N-body simulations
narrower: Orbital resonances
narrower: Three-body problem
narrower: Tidal interaction
narrower: Two-body problem
narrower: Dynamical friction
contributor: AAS Frey.Katie
definition: Mutual attraction between any two bodies that have mass.
modified: 2020-11-09T15:54:23.607Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:54:33.562Z
modified: 2020-11-09T15:54:33.594Z

Armillary spheres
type: Concept
alternative label: Armil
alternative label: Armilla
alternative label: Spherical astrolabes
broader: Early astronomical instruments
definition: An ancient instrument, used since ancient times until the Middle ages and later, to determine positions of celestial bodies. It consisted of an assemblage of rings, all circles of the same sphere, designed to represent the positions of the important circles of the celestial sphere.
modified: 2020-10-26T18:44:59.166Z
contributor: AAS Frey.Katie
modified: 2020-10-26T18:45:15.929Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:45:15.903Z
  creator: AAS Frey.Katie

Gravitational lensing
type: Concept
alternative label: Gravitational lens
broader: General relativity
narrower: Strong gravitational lensing
narrower: Weak gravitational lensing
narrower: Einstein rings
narrower: Gravitational lensing shear
narrower: Gravitational microlensing
narrower: Caustic curve
narrower: Critical curve
contributor: AAS Frey.Katie
definition: A concentration of matter, such as a galaxy or a cluster of galaxies, that bends light rays from a background object, resulting in production of multiple images. If the two objects and the Earth are perfectly aligned, the light from the distant object appears as a ring from Earth. This is called an Einstein Ring, since its existence was predicted by Einstein in his theory of general relativity.
modified: 2020-11-09T15:56:40.920Z
modified: 2020-11-09T15:56:52.171Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:56:52.144Z

Gravitational lensing shear
type: Concept
broader: Gravitational lensing

Gravitational microlensing
type: Concept
alternative label: Microlensing
broader: Gravitational lensing
narrower: Quasar microlensing
related: Free floating planets
alternative label: Planetary microlensing
narrower: Binary lens microlensing
narrower: Triple lens microlensing
narrower: High-resolution microlensing event imaging
narrower: Astrometric microlensing effect
narrower: Binary source microlensing
narrower: Finite-source photometric effect
narrower: Lens orbital motion
narrower: Microlensing parallax
narrower: Microlensing optical depth
narrower: Microlensing event rate
narrower: Gravitational microlensing exoplanet detection
alternative label: Gravitational microlens
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:15:33.423Z

Gravitational singularities
type: Concept
alternative label: Cosmic singularities
alternative label: Singularity
alternative label: Space-time singularities
alternative label: Spacetime singularities
broader: General relativity
narrower: Naked singularities
narrower: Ring singularities
narrower: Wormholes
narrower: Conical singularities
narrower: Curvature singularities
narrower: Event horizons
related: Black holes

Gravitational wave astronomy
type: Concept
broader: Astronomical methods
related: Gravitational waves

Gravitational wave detectors
type: Concept
broader: Astronomical detectors
related: Gravitational waves

Gravitational wave sources
type: Concept
broader: Gravitational waves

Gravitational waves
type: Concept
broader: Cosmic inflation
broader: General relativity
broader: Particle astrophysics
narrower: pp waves
narrower: Gravitational wave sources
related: Gravitational wave astronomy
related: Gravitational wave detectors
scope note: Not to be confused with a gravity wave.
contributor: AAS Frey.Katie Admin
definition: A space-time oscillation created by the motion of matter, as predicted by Einstein's general relativity. When an object accelerates, it creates ripples in space-time, just like a boat causes ripples in a lake. Gravitational waves are extremely weak even for the most massive objects like supermassive black holes. They had been inferred from observing a binary pulsar in which the components slow down, due to losing energy from emitting gravitational waves. Gravitational waves were directly detected for the first time on September 14, 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Since then several other events have been detected by LIGO and Laser Interferometer Space Antenna (LISA).
modified: 2020-11-02T15:53:54.260Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T15:54:10.549Z
modified: 2020-11-02T15:54:10.582Z

Gravity anomaly
type: Concept
broader: Newtonian gravitation
narrower: Mascon
narrower: Great Attractor

Artificial satellites
type: Concept
broader: Space vehicles
narrower: Geosynchronous satellites
definition: A man-made equipment that orbits around Earth or a solar system body.
contributor: AAS Frey.Katie
modified: 2020-10-26T18:45:44.172Z
modified: 2020-10-26T18:46:00.033Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:46:00.005Z
  creator: AAS Frey.Katie

Gravity darkening
type: Concept
alternative label: Gravity brightening
broader: Stellar rotation
contributor: AAS Frey.Katie
definition: The darkening, or brightening, of a region on a star due to localized decrease, or increase, in the effective gravity. Gravity darkening is explained by the von Zeipel theorem, whereby on stellar surface the radiative flux is proportional to the effective gravity. This means that in rotating stars regions close to the pole are brighter (and have higher temperature) than regions close to the equator. Gravity darkening occurs also in corotating binary systems, where the tidal force leads to both gravity darkening and gravity brightening. The effects are often seen in binary star light curves. Recent theoretical work has shown that gravity darkening is not well represented by the von Zeipel theorem. This is supported by new interferometric observations of some rapidly rotating stars indicating that the von Zeipel theorem seems to overestimate the temperature difference between the poles and equator.
modified: 2020-11-09T15:57:56.988Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T15:58:09.727Z
modified: 2020-11-09T15:58:09.757Z

Grazing incidence telescopes
type: Concept
alternative label: Grazing-incidence telescopes
broader: Telescopes

Great Attractor
type: Concept
broader: Gravity anomaly
broader: Large-scale structure of the universe
contributor: AAS Frey.Katie
definition: A hypothesized large concentration of mass (about 10^16 solar masses), some hundred million light-years from Earth, in the direction of the Centaurus supercluster, that seems to be affecting the motions of many nearby galaxies by virtue of its gravity.
modified: 2020-11-09T15:58:53.317Z
modified: 2020-11-09T15:59:03.480Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T15:59:03.452Z
  creator: AAS Frey.Katie

Green valley galaxies
type: Concept
broader: Galaxy colors

Greenhouse gases
type: Concept
narrower: Methane
narrower: Nitrous oxide
narrower: Water vapor
narrower: Carbon dioxide
narrower: Chlorofluorocarbons
definition: Gases responsible for the greenhouse effect. These gases include: water vapor; carbon dioxide; methane; nitrous oxide; chlorofluorocarbons; and tropospheric ozone.
broader: Greenhouse effect
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:19:17.357Z
modified: 2020-11-09T16:02:41.231Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:02:41.199Z
contributor: AAS Frey.Katie

Gregorian telescopes
type: Concept
broader: Reflecting telescopes

Ground-based astronomy
type: Concept
alternative label: Ground based astronomy
broader: Astronomical methods
contributor: AAS Frey.Katie
definition: Astronomical study carried out using a telescope on Earth, as opposed to that from an orbiting satellite.
modified: 2020-11-09T16:03:16.344Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:03:26.470Z
  creator: AAS Frey.Katie
modified: 2020-11-09T16:03:26.502Z

Ground telescopes
type: Concept
alternative label: Ground based telescopes
alternative label: Ground-based telescopes
broader: Telescopes

Gunn photometry
type: Concept
alternative label: Gunn g,r,i,z photometry
broader: Broad band photometry

H-alpha stars
type: Concept
broader: Emission line stars

Ascending node
type: Concept
alternative label: North node
broader: Orbital nodes
contributor: AAS Frey.Katie
modified: 2020-11-03T18:21:44.908Z
definition: The point in an orbit where the orbiting body crosses a reference plane, such as the ecliptic or the celestial equator, going from south to north. The celestial longitude of the ascending node is one of the elements of the orbit.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:22:01.177Z
  creator: AAS Frey.Katie
modified: 2020-11-03T18:22:01.207Z

H alpha photometry
type: Concept
broader: Narrow band photometry

H beta photometry
type: Concept
broader: Narrow band photometry

H I regions
type: Concept
alternative label: HI regions
broader: Nebulae
narrower: HI shells
related: Astrochemistry
modified: 2020-11-02T15:57:58.504Z
definition: A region of neutral (atomic) hydrogen in interstellar space. At least 95 percent of interstellar hydrogen is H I. It emits radio waves that are 21 cm long.
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T15:58:10.193Z
modified: 2020-11-02T15:58:10.217Z

H II regions
type: Concept
alternative label: H I I clouds
alternative label: H I I regions
alternative label: H II clouds
alternative label: HII clouds
alternative label: HII regions
broader: Emission nebulae
narrower: Bok globules
narrower: Compact H II region
contributor: AAS Frey.Katie
definition: A type of emission nebulae composed of very hot gas (about 10^4 K), mainly ionized hydrogen, created by the ultraviolet radiation of massive stars. H II regions originate when O or early-type stars, born in giant molecular clouds, start heating up the cold gas, causing it to become ionized and 'glow'. The effective temperatures of the exciting stars are in the range 3 x 10^4 to 5 x 10^4 K, and throughout the nebula hydrogen is ionized. Helium is singly ionized, and other elements are mostly singly or doubly ionized. Typical densities in the H II region are of the order 10 to 10^2 cm^-3, ranging as high as 10^4 cm^-3. Internal motions occur in the gas with velocities of order 10 km s^-1. The spectra of H II regions are mainly composed of strong H I recombination lines and forbidden lines such as [O III], [O II], [N II].
modified: 2020-11-09T16:04:53.108Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T15:59:55.369Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T15:59:55.394Z

Habitable planets
type: Concept
broader: Exoplanets

Habitable zone
type: Concept
broader: Planet hosting stars
definition: A zone around a star where the temperature would be in the range 0-100 °C to sustain liquid water on the surface of rocky planets (or sufficiently large moons). Water is thought to be a necessary component to the formation and evolution of Earth-type life. This zone depends on the parent star's luminosity and distance; it will be farther from hotter stars. A more accurate definition of a Habitable Zone needs to include other factors, such as orbital eccentricity, heat sources other than stellar irradiation, and atmospheric properties.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:01:29.462Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:01:45.295Z
modified: 2020-11-02T16:01:45.324Z

Hadron barrier
type: Concept
alternative label: Hadron epoch
broader: Big Bang theory

Hall thrusters
type: Concept
alternative label: Hall current thrusters
alternative label: Hall effect thrusters
broader: Space vehicles

Halo stars
type: Concept
broader: High-velocity stars

Asteroid belt
type: Concept
broader: Solar system
related: Asteroids
definition: The region of the solar system located between Mars and Jupiter where over a million objects bigger than 1 km across orbit the Sun.
related: Main belt asteroids
contributor: AAS Frey.Katie Admin
modified: 2020-12-02T21:49:42.735Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:22:52.514Z
modified: 2020-11-03T18:22:52.543Z
contributor: AAS Frey.Katie

Hardness ratio
type: Concept
broader: X-ray photometry

Haro galaxies
type: Concept
broader: Active galaxies
definition: A type of galaxies characterized by strong emission in the blue and violet regions of the spectrum. They are often elliptical or lenticular.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:05:37.476Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:05:49.645Z
modified: 2020-11-02T16:05:49.676Z

Hawking radiation
type: Concept
alternative label: Black hole evaporation
broader: Black hole physics
contributor: AAS Frey.Katie
definition: The radiation produced by a black hole when quantum mechanical effects are taken into account. According to quantum physics, large fluctuations in the vacuum energy occurs for brief moments of time. Thereby virtual particle-antiparticle pairs are created from vacuum and annihilated. If pair production happens just outside the event horizon of a black hole, as soon as these particles are formed they would both experience drastically different gravitational attractions due to the sharp gradient of force close to the black hole. One particle will accelerate toward the black hole and its partner will escape into space. The black hole used some of its gravitational energy to produce these two particles, so it loses some of its mass if a particle escapes. This gradual loss of mass over time means the black hole eventually evaporates out of existence.
modified: 2020-11-09T16:10:59.094Z
modified: 2020-11-09T16:11:12.113Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:11:12.084Z
  creator: AAS Frey.Katie

Hayashi track
type: Concept
broader: Stellar evolutionary tracks
contributor: AAS Frey.Katie
related: Hertzsprung Russell diagram
modified: 2020-11-09T16:11:44.337Z
definition: The path on the Hertzsprung-Russell diagram that is followed by a fully convective pre-main sequence star to reach the zero-age main sequence. Hayashi tracks for low-mass stars are near vertical. At higher masses, stars become increasingly radiative as they contract and the Hayashi tracks are almost horizontal.
editorial note: Definition Provenance
  created: 2020-11-09T16:11:54.309Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T16:11:54.343Z

Heavy metal stars
type: Concept
alternative label: Heavy-metal stars
broader: Chemically peculiar stars
broader: Late-type giant stars
narrower: Manganese stars
narrower: Barium stars
narrower: S stars
narrower: Strontium stars
narrower: Technetium stars

Heliocentric orbit
type: Concept
broader: Orbital motion

Heliopause
type: Concept
broader: Solar wind
broader: Heliosphere
contributor: AAS Frey.Katie
modified: 2020-11-09T16:12:22.822Z
definition: The edge of the solar system where the pressure of the solar wind balances that of the interstellar medium plasma. In other words, the surface boundary that separates the heliosphere from interstellar space. It is estimated to be situated 100 astronomical units or more from the Sun. A bow shock likely forms as the interstellar medium wind approaches the heliosphere and is deflected around the heliosphere, forcing it into a teardrop-shaped structure with a long, comet-like tail.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:12:33.501Z
modified: 2020-11-09T16:12:33.531Z

Helioseismology
type: Concept
broader: Solar physics
narrower: Solar cycle
narrower: Solar magnetic fields
narrower: Helioseismic pulsations
contributor: AAS Frey.Katie
related: Solar interior
related: Asteroseismology
modified: 2020-11-09T16:13:23.555Z
definition: The branch of astrophysics that investigates the interior structure of the Sun by studying its surface wave oscillations. The surface of the Sun vibrates much like a bell. A piano has 88 keys or musical tones, whereas the Sun has millions of notes. These vibrations are the result of internal pressure waves that reflect off the photosphere and repeatedly cross the solar interior. They are detected through the Doppler shift of absorption lines formed in the photosphere. Because these vibrations make the solar surface move up and down, analysis of the surface patterns is used to study conditions far below the Sun's surface. The mean period of the vibrations is about five minutes, which corresponds to a frequency of about 3 mHz.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:13:36.360Z
modified: 2020-11-09T16:13:36.389Z

Asteroid occultation
type: Concept
broader: Occultation

Heliosheath
type: Concept
broader: Heliosphere
contributor: AAS Frey.Katie
definition: The region located between the termination shock and the heliopause where the turbulent and hot solar wind is compressed as it passes outward against the interstellar wind.
modified: 2020-11-09T16:14:14.801Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:14:29.534Z
modified: 2020-11-09T16:14:29.566Z

Heliosphere
type: Concept
broader: Solar system
broader: Stellar wind bubbles
narrower: Stellar bow shocks
narrower: Termination shock
narrower: Heliopause
narrower: Heliosheath
related: Astrosphere interstellar medium interactions
contributor: AAS Frey.Katie
definition: The vast, three-dimensional region of space around the Sun filled with the solar wind and the remnant of the solar magnetic field carried in it. It is bounded by the heliopause, which is estimated to be 100 astronomical units or more from the Sun. The radius of the heliosphere is expected to vary with the solar cycle. The heliosphere may be very elongated owing to the presence of an interstellar wind of neutral hydrogen flowing from the direction of the Galactic center.
modified: 2020-11-09T16:14:57.453Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-09T16:15:08.012Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T16:15:08.038Z

Heliostats
type: Concept
broader: Stellar tracking devices
definition: An instrument consisting of a mirror moved by clockwork for tracking the movement of the Sun and reflecting the sunlight into a stationary solar telescope. A heliostat is similar to a coelostat.
modified: 2020-11-02T16:08:40.713Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:08:54.644Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-02T16:08:54.676Z

Helium-rich stars
type: Concept
alternative label: Helium rich stars
broader: Chemically peculiar stars
narrower: DB stars
alternative label: Helium strong stars
contributor: AAS Frey.Katie
modified: 2020-10-21T20:21:43.544Z

Helium burning
type: Concept
broader: Nucleosynthesis
broader: Stellar nucleosynthesis
contributor: AAS Frey.Katie
definition: The stage in the evolution of a star, after the exhaustion of hydrogen, when the star produces its energy by the fusion of helium into carbon and oxygen.
modified: 2020-11-09T16:16:36.760Z
editorial note: Definition Provenance
  created: 2020-11-09T16:16:46.626Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T16:16:46.654Z

Helium-weak stars
type: Concept
alternative label: CP4
alternative label: He-weak stars
broader: Chemically peculiar stars
narrower: BW stars
alternative label: Helium poor stars
alternative label: Helium-poor stars
alternative label: Helium weak stars
definition: Chemically peculiar stars with very weak helium lines. Examples include 3 Sco, HD 176582, HD 217833, HR 2949, and HD 21699. The He-weak stars do not form a homogeneous group. Some of them display intense Si, or Ti and Sr lines, and are considered a hot extension of the magnetic Ap/Bp stars. Others show overabundances of P and Ga, typically noted for HgMn stars. The star HD 139160 belongs to the non-magnetic subgroup of He-weak stars.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:32:19.876Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:17:33.370Z
modified: 2020-11-09T16:17:33.394Z

Henry Draper catalog
type: Concept
alternative label: HD catalog
broader: Catalogs
broader: Stellar classification
alternative label: Harvard classification
preferred label: Henry Draper catalogue
alternative label: Henry Draper Catalogue
contributor: AAS Frey.Katie
definition: A catalog of stars in which every star is classified by its stellar spectrum. Though named for the astronomer Henry Draper, it was cataloged by Annie J. Cannon (225,300 stars), and later extended by Margaret W. Mayall.
modified: 2022-01-03T15:50:14.122Z
modified: 2020-11-09T16:34:06.948Z
editorial note: Definition Provenance
  created: 2020-11-09T16:34:06.907Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Asteroids
type: Concept
broader: Small Solar System bodies
narrower: Trojan asteroids
narrower: Hilda group
narrower: Hirayama families
narrower: Hungaria group
related: Asteroid belt
related: Interplanetary medium
narrower: Main belt asteroids
alternative label: Asteroid
definition: A small rocky object orbiting the Sun. There are millions of asteroids moving in orbits in the main asteroid belt, between Mars and Jupiter and in the Kuiper belt. The largest and the first discovered, Ceres, about 1,000 km in size, is now classified as dwarf planet (2006 IAU General Assembly). The largest asteroid in the solar system (Ceres apart), is Pallas, with a size of 582 x 556 x 500 km. On the other hand, the smallest asteroid ever studied is the 2 meters space rock 2015 TC25, which was observed when it made a close flyby of Earth in October 2015.
narrower: Centaur group
related: Near-Earth objects
alternative label: Minor planets
narrower: Asteroid surfaces
related: Asteroid dynamics
narrower: Asteroid satellites
contributor: AAS Frey.Katie Admin
modified: 2022-01-04T19:17:46.187Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T18:47:28.215Z
modified: 2020-10-26T18:47:28.243Z

Henyey track
type: Concept
broader: Stellar evolutionary tracks
contributor: AAS Frey.Katie
related: Hertzsprung Russell diagram
definition: A nearly horizontal path on the Hertzsprung-Russell diagram that a pre-main sequence star of small mass follows in an early stage of evolution after leaving the Hayashi track and before reaching the main sequence. During this stage the pre-main sequence star remains almost wholly in radiative equilibrium.
modified: 2020-11-09T16:34:37.042Z
editorial note: Definition Provenance
  created: 2020-11-09T16:34:48.437Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T16:34:48.469Z

Hertzsprung gap
type: Concept
broader: Hertzsprung Russell diagram
contributor: AAS Frey.Katie
definition: A region of the Hertzsprung-Russell diagram, between the main sequence and the giant branch, occupied by very few stars. It corresponds to a very short period in stellar evolution.
modified: 2020-11-09T16:35:32.989Z
editorial note: Definition Provenance
  created: 2020-11-09T16:35:42.764Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T16:35:42.796Z

Hertzsprung Russell diagram
type: Concept
alternative label: Color-color diagrams of stars
alternative label: Color-magnitude diagrams of stars
alternative label: H-R diagrams
alternative label: HR diagram
alternative label: HRD
alternative label: Hertzsprung-Russell diagram
narrower: Pre-main sequence
alternative label: Hertzsprung/Russell diagrams
alternative label: Hertzsprung–Russell diagram
narrower: Post-asymptotic giant branch
narrower: Blue loop
narrower: Turnoff point
narrower: Giant branch
narrower: Hertzsprung gap
narrower: Instability strip
alternative label: Hertzsprung Russell diagrams
related: Stellar physics
related: Zero-age main sequence stars
related: Evolved stars
alternative label: Hertzsprung-Russell diagrams
narrower: Asymptotic giant branch
related: Stellar evolutionary types
broader: Stellar evolutionary models
narrower: Main sequence
narrower: Horizontal branch
related: Hayashi track
contributor: AAS Frey.Katie
related: Henyey track
related: Zero-age horizontal branch stars
modified: 2020-11-09T16:36:16.164Z
definition: A display of stellar properties using a plot of effective temperature (or instead color or spectral type) along the abscissa versus luminosity (or absolute magnitude). The temperature is plotted in the inverse direction, with high temperatures on the left and low temperatures on the right. On the diagram the majority of stars are concentrated in a diagonal strip running from upper left to lower right, i.e. from high temperature-high luminosity massive stars to low temperature-low luminosity low-mass stars. This feature is known as the main sequence. This is the locus of stars burning hydrogen in their cores (proton-proton chain). The lower edge of this strip, known as the zero age main sequence (ZAMS), designates the positions where stars of different mass first begin to burn hydrogen in their cores. Well below the main sequence there is a group of stars that, despite being very hot, are so small that their luminosity is very small as a consequence. These are the class of white dwarfs. These objects represent old and very evolved stars that have shed their outer layers to reveal a very small but extremely hot inner core. They are no longer generating energy but are merely emitting light as they cool (white dwarf cooling track). Stars with high luminosities but relatively low temperatures occupy a wide region above the main sequence. The majority of them have used up all the hydrogen in their cores and have expanded and cooled as a result of internal readjustment. Called red giants, they are still burning helium in their cores (helium burning, carbon burning). There are also stars with very high luminosities, resulting from their enormous outputs of energy, because they are burning their fuel at a prodigious rate. These are the supergiants. They can be hot or cool, hence blue or red in color.
modified: 2020-11-09T16:36:26.140Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-09T16:36:26.112Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Heterodyne interferometry
type: Concept
broader: Interferometry

Heterodyne receivers
type: Concept
alternative label: Superhet
alternative label: Superheterodyne receivers
broader: Radio telescopes

HI shells
type: Concept
alternative label: H I shells
broader: H I regions

Hickson compact group
type: Concept
alternative label: HCG
broader: Galaxy groups
alternative label: Compact group of galaxies
contributor: AAS Frey.Katie
definition: A list of 100 compact groups of galaxies that were identified by a systematic search of the Palomar Observatory Sky Survey red prints. Each group contains four or more galaxies, has an estimated mean surface brightness brighter than 26.0 magnitude per arcsec2 and satisfies an isolation criterion.
modified: 2024-06-20T12:32:24.578Z
editorial note: Definition Provenance
  created: 2024-06-20T12:32:38.072Z
  creator: AAS Frey.Katie
  comment: Hickson, Paul, 1982, ApJ 255, 382
modified: 2024-06-20T12:32:38.079Z

Asteroseismology
type: Concept
alternative label: Astroseismology
alternative label: Stellar seismology
broader: Stellar astronomy
narrower: Oblique rotators
narrower: Stellar magnetic fields
narrower: Stellar oscillations
contributor: AAS Frey.Katie
related: Helioseismology
definition: The study of the internal structure of stars through the interpretation of their pulsation periods (stellar pulsation). The radial pulsations are the result of sound waves resonating in the stars interior. Different pulsation modes penetrate to different depths inside a star. If a large number of pulsation modes occurs, then the stellar interior, which is not directly observable, can be probed from oscillation studies because the modes penetrate to various depths inside the star. Using a complex mathematical analysis, very detailed investigations of the structure of the star's interior can be carried out. Applied to the Sun, it is called helioseismology.
modified: 2020-11-03T18:24:20.455Z
editorial note: Definition Provenance
  created: 2020-11-03T18:24:33.522Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-03T18:24:33.550Z

Hierarchical cosmology
type: Concept
broader: Cosmology
contributor: AAS Frey.Katie
definition: A cosmology characterized by clustering of galaxy clusters in increasingly larger systems.
modified: 2020-11-09T16:36:55.624Z
modified: 2020-11-09T16:37:09.054Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:37:09.026Z

High-energy cosmic radiation
type: Concept
alternative label: High energy cosmic radiation
alternative label: High energy cosmic rays
alternative label: High-energy cosmic rays
broader: Cosmic rays

High mass x-ray binary stars
type: Concept
alternative label: HMXBs
broader: X-ray binary stars
broader: Massive stars
alternative label: High-mass X-ray binary stars
alternative label: High-mass X-ray binaries
alternative label: HMXB
contributor: AAS Frey.Katie Admin
definition: A member of one of the two main classes of X-ray binary systems where one of the components is a neutron star or a black hole and the other one a massive star. HMXBs emit relatively hard X-rays and usually show regular pulsations, no X-ray bursts, and often X-ray eclipses. Their X-ray luminosity is much larger than their optical luminosity. In our Galaxy HMXBs are found predominantly in the spiral arms and within the Galactic disk in young stellar populations less than 10^7 years old. One of the most famous HMXB is Cygnus X-1 which was the first stellar-mass black hole discovered.
modified: 2020-11-02T16:38:32.319Z
modified: 2020-11-02T16:38:50.422Z
editorial note: Definition Provenance
  created: 2020-11-02T16:38:50.389Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

High-redshift galaxies
type: Concept
broader: Galaxies

High-velocity clouds
type: Concept
alternative label: HVC
alternative label: High velocity clouds
broader: Interstellar clouds
narrower: Magellanic Stream
definition: A population of neutral or partly ionized gas clouds in the Galactic halo which are seen as high-altitude structures in the atomic hydrogen 21 cm emission at high radial velocities (v_LSR > 100 km/sec). They have substantial neutral column densities (> 10^19 cm^-2) and their metallicities range from 0.1 to about 1.0 times solar. The distances to the majority of them remain unknown. They may represent the continuing infall of matter onto the Local Group.
modified: 2020-11-02T16:39:58.316Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-02T16:40:12.759Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-02T16:40:12.792Z

High-velocity stars
type: Concept
alternative label: High velocity stars
broader: Galaxies
narrower: Runaway stars
narrower: Halo stars
narrower: Hypervelocity stars

High altitude balloons
type: Concept
alternative label: High-altitude balloons
broader: Astronomical instrumentation

High energy astrophysics
type: Concept
alternative label: High energy astronomy
alternative label: High energy process
alternative label: High-energy astronomy
alternative label: High-energy astrophysics
alternative label: High-energy process
narrower: Neutrino astronomy
narrower: Plasma astrophysics
narrower: Relativistic binary stars
narrower: Seyfert galaxies
narrower: Black hole physics
narrower: Active galactic nuclei
narrower: Black holes
narrower: Warm-hot intergalactic medium
narrower: Transient sources
narrower: Burst astrophysics
narrower: Dark matter
narrower: Intracluster medium
narrower: Jets
narrower: Particle astrophysics
top concept of: The Unified Astronomy Thesaurus
definition: A branch of astrophysics that deals with objects emitting highly energetic radiation, such as X-ray astronomy, gamma-ray astronomy, and extreme ultraviolet astronomy, as well as neutrinos and cosmic rays.
modified: 2020-11-02T16:36:54.778Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:37:15.256Z
modified: 2020-11-02T16:37:15.291Z

Astrobiology
type: Concept
alternative label: Extraterrestrial life
alternative label: Space biology
broader: Interdisciplinary astronomy
narrower: Xenobiology
narrower: Biosignatures
alternative label: Exobiology
related: Pre-biotic astrochemistry
narrower: Search for extraterrestrial intelligence
definition: The study of life throughout the Universe, also known as exobiology.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:28:18.112Z
modified: 2020-11-03T18:25:14.876Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:25:14.847Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie

Hilda group
type: Concept
broader: Asteroids
alternative label: Hilda asteroids
contributor: AAS Frey.Katie Admin
definition: The asteroids found on the outer edge of the main asteroid belt in a 2:3 orbital resonance with Jupiter. The group is not an asteroid family since the members are not physically related. The group consists of asteroids with semi-major axes between 3.70 AU and 4.20 AU, eccentricities less than 0.30, and inclinations less than 20°. It is dominated by D- and P-type asteroids.
modified: 2020-12-09T15:41:15.849Z
editorial note: Definition Provenance
  created: 2020-11-02T16:43:34.440Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-02T16:43:34.469Z

Hirayama families
type: Concept
broader: Asteroids
modified: 2020-12-09T15:41:24.627Z
contributor: AAS Frey.Katie Admin

Holmberg radius
type: Concept
broader: Galaxy distances

Holmium stars
type: Concept
broader: Ap stars

Holographic interferometry
type: Concept
broader: Interferometry

Horizontal branch stars
type: Concept
alternative label: HB stars
alternative label: Horizontal-branch stars
narrower: Zero-age horizontal branch stars
narrower: Extreme horizontal branch stars
contributor: AAS Frey.Katie Admin
related: Horizontal branch
alternative label: Horizontal branch star
broader: Stellar evolutionary types
definition: A star lying on the horizontal branch.
modified: 2020-11-02T16:46:37.559Z
modified: 2020-11-02T16:46:51.582Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:46:51.554Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Horizontal coordinate system
type: Concept
alternative label: Alt/Az coordinate system
alternative label: Horizon (horizon coordinate system)
alternative label: Horizon coordinate system
alternative label: az/el coordinate system
broader: Astronomical coordinate systems
narrower: Meridian
narrower: Nadir
narrower: Azimuth
narrower: Vertical circle
narrower: Zenith
narrower: Altitude angle
definition: The coordinate system based on the position of the observer. The horizontal plane is the fundamental plane and the coordinates are altitude and azimuth.
modified: 2020-11-02T16:48:41.417Z
contributor: AAS Frey.Katie Admin
narrower: Horizon
narrower: Cardinal directions
narrower: Zenith distance
editorial note: Definition Provenance
  created: 2020-11-02T16:48:54.862Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-02T16:48:54.890Z

Horizontal parallax
type: Concept
broader: Diurnal parallax
contributor: AAS Frey.Katie
modified: 2020-11-09T16:42:57.140Z
definition: The angle under which the radius of the Earth at the place of observation would be seen from a celestial body when it is in the horizon (at the instant of rising or setting). The amount varies with the latitude since the Earth is not exactly spherical, and is greatest at equator.
editorial note: Definition Provenance
  created: 2020-11-09T16:43:08.166Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-09T16:43:08.200Z

Astrochemistry
type: Concept
narrower: Chemical abundances
narrower: CII region
narrower: Cosmochemistry
narrower: Diffuse interstellar bands
related: H I regions
narrower: Polycyclic aromatic hydrocarbons
broader: Interdisciplinary astronomy
narrower: Pre-biotic astrochemistry
narrower: Reaction catalysts
narrower: Reaction rates
narrower: Spectral line lists
contributor: AAS Frey.Katie
modified: 2020-11-03T18:25:39.898Z
definition: The study of the chemical interactions between the gas and dust of the interstellar medium.
modified: 2020-11-03T18:25:50.686Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:25:50.616Z
  creator: AAS Frey.Katie

Hot dark matter
type: Concept
alternative label: HDM
broader: Dark matter
contributor: AAS Frey.Katie
definition: Any form of dark matter which had a significant velocity dispersion (comparable to the velocity of light), when the Universe first became matter-dominated.
modified: 2020-11-09T16:43:34.571Z
modified: 2020-11-09T16:43:44.714Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:43:44.685Z

Hot intergalactic medium
type: Concept
broader: Intergalactic medium phases

Hot ionized medium
type: Concept
alternative label: HIM
broader: Interstellar phases
preferred label: Hot ionised medium
modified: 2021-09-27T15:43:58.312Z
contributor: AAS Frey.Katie Admin

Hot Jupiters
type: Concept
alternative label: Epistellar jovians
alternative label: Pegasean planets
alternative label: Pegasids
alternative label: Roaster planets
broader: Exoplanets
contributor: AAS Frey.Katie
definition: A giant, gaseous, Jupiter-like planet lying too close to its parent star and having an orbital period from a few days to a few weeks. The existence of hot Jupiters is usually interpreted in terms of planetary migration. These planets can, in principle, be formed at larger distances from their stars and migrate to the inner regions due to dynamical interaction with the proto-planetary disk.
modified: 2020-11-09T16:44:20.723Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:44:31.561Z
modified: 2020-11-09T16:44:31.603Z

Hot Neptunes
type: Concept
broader: Exoplanets

Hour angle
type: Concept
broader: Equatorial coordinate system
contributor: AAS Frey.Katie
modified: 2020-11-09T16:44:57.790Z
definition: A telescope based coordinate specifying the angle, in the equatorial plane, from the meridian to a plane containing the celestial object and the north and south celestial poles.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:45:08.166Z
modified: 2020-11-09T16:45:08.193Z

Hubble classification scheme
type: Concept
alternative label: Hubble classification
alternative label: Hubble galaxy classification
alternative label: Hubble sequence
alternative label: Hubble's classification
broader: Galaxy classification systems
related: Spiral galaxies
related: Elliptical galaxies
related: Irregular galaxies
related: Lenticular galaxies
contributor: AAS Frey.Katie
definition: The classification of galaxies according to their visual appearance into four basic types suggested by E. Hubble: ellipticals (E), spirals (S), barred spirals (SB), and irregulars (Ir). Later on a separate class of lenticulars (S0) was appended as an intermediate type between ellipticals and spirals. The sequence starts with round elliptical galaxies (E0). Flatter galaxies are arranged following a number which is calculated from the ratio (a - b)/a, where a and b are the major and minor axes as measured on the sky. Ellipticals are divided into eight categories (E0, E1, ..., E7). Beyond E7 a clear disk is apparent in the lenticular (S0) galaxies. The sequence then splits into two parallel branches of disk galaxies showing spiral structure: ordinary spirals, S, and barred spirals, SB. The spiral and barred types are subdivided into Sa, Sb, Sc, and SBa, SBb, SBc, respectively. Along the sequence from Sa to Sc, the central bulge becomes smaller, while the spiral arms become more and more paramount. The original, erroneous idea that such arrangement of the galaxies might represent an evolutionary sequence led to the ellipticals being referred to as early-type galaxies, and the spirals and Irr I irregulars as late-type galaxies.
modified: 2020-11-09T16:45:49.001Z
modified: 2020-11-09T16:46:01.044Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:46:01.015Z

Hubble constant
type: Concept
broader: Observational cosmology
broader: Cosmological parameters
contributor: AAS Frey.Katie
alternative label: Hubble-Lemaitre constant
definition: The Hubble parameter for the present epoch. It is the constant of proportionality between the recession velocities of galaxies and their distances from each other. The latest determinations using the Hubble Space Telescope observations of Cepheids give H_0 = 72 ± 8 km s^-1 Mpc^-1, the WMAP observations yield 70.4 ± 1.3 km s^-1 Mpc^-1, and the Planck Satellite observations give 67.3 ± 1.2 km s^-1 Mpc^-1. More recently, the Hubble constant was derived by a team of astronomers, using the NASA/ESA Hubble Space Telescope, with a 2.4% accuracy. The new value, 73.2 km s^-1 Mpc^-1, suggests that the Universe is expanding between five and nine percent faster than previously calculated. The Hubble law is only applicable for large distances (> 20 Mpc), when the proper motions of galaxies in groups and clusters cannot confuse the recession due to expansion.
modified: 2020-11-09T16:47:15.548Z
modified: 2020-11-09T16:47:25.946Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:47:25.916Z

Hubble diagram
type: Concept
broader: Hubble-Lemaitre law
contributor: AAS Frey.Katie
definition: A plot of the redshift of galaxies against their distance or against their apparent magnitude.
modified: 2020-11-09T16:47:51.519Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:48:01.361Z
modified: 2020-11-09T16:48:01.391Z

Astrodynamics
type: Concept
alternative label: Orbital mechanics
broader: Celestial mechanics
contributor: AAS Frey.Katie
definition: The science dealing with the motion of satellites, rockets, and spacecrafts. It uses the principles of celestial mechanics.
modified: 2020-11-03T18:26:20.372Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:26:33.319Z
modified: 2020-11-03T18:26:33.349Z

Hubble radius
type: Concept
broader: Galaxy distances
contributor: AAS Frey.Katie
modified: 2020-11-09T16:48:30.659Z
definition: The size of the observable Universe as derived from the ratio c/H_0, where H_0 is the Hubble-Lemaitre constant and c the speed of light.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:48:41.967Z
modified: 2020-11-09T16:48:42.003Z

Hubble Space Telescope
type: Concept
alternative label: HST
broader: Optical observatories
broader: Space observatories
broader: Ultraviolet observatories
definition: A telescope of 2.4 m in diameter, a joint NASA and ESA project, launched in 1990 into a low-Earth orbit 600 km above the ground. It was equipped with a collection of several science instruments that worked across the entire optical spectrum (from infrared, through the visible, to ultraviolet light). During its lifetime Hubble has become one of the most important science projects ever.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T16:53:09.153Z
modified: 2020-11-02T16:53:34.807Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T16:53:34.780Z

Hubble time
type: Concept
alternative label: Expansion timescale
broader: Cosmological parameters
contributor: AAS Frey.Katie
definition: An estimate for the age of the Universe by presuming that the Universe has always expanded at the same rate as it is expanding today. It is the inverse of the Hubble-Lemaitre constant.
modified: 2020-11-09T16:49:42.708Z
editorial note: Definition Provenance
  created: 2020-11-09T16:49:52.940Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T16:49:52.972Z

Hubble-Lemaitre law
type: Concept
alternative label: Hubble law
broader: Origin of the universe
narrower: Hubble diagram
contributor: AAS Frey.Katie Admin
alternative label: Hubble's law
modified: 2020-12-17T16:50:34.706Z
definition: The speed with which a galaxy cluster recedes from us is directly proportional to its distance. It can be stated as v = H_{0}d, where v is the recessional velocity, H_0 the Hubble-Lemaitre constant, and d the distance.
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T16:59:40.828Z
  creator: AAS Frey.Katie Admin
change note: Name change
  comment: The International Astronomical Union (IAU) at its 30th Meeting approved the Resolution B4 proposed by the IAU Executive Committee recommending the use of Hubble-Lemaitre law instead of Hubble's law, after Edwin Hubble (1889-1953), the American astronomer who published his results in 1929 and Georges Lemaître, Belgian priest and astronomer, who published a paper on the expansion of the Universe in 1927. From An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri.
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T17:00:19.047Z
modified: 2020-11-02T17:00:19.079Z

Humidity
type: Concept
broader: Earth atmosphere
contributor: AAS Frey.Katie
definition: Generally, a measure of the water vapor content of the air. Popularly, it is used synonymously with relative humidity.
modified: 2020-11-09T16:50:51.069Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:51:00.544Z
modified: 2020-11-09T16:51:00.574Z

Hungaria group
type: Concept
broader: Asteroids
contributor: AAS Frey.Katie Admin
modified: 2020-12-09T15:41:32.193Z

Hydrogen burning
type: Concept
broader: Nucleosynthesis
broader: Stellar nucleosynthesis
narrower: Proton-proton reaction
narrower: Carbon-nitrogen cycle
definition: A series of thermonuclear reactions, taking place mainly in low-mass stars, such as the Sun, which transforms four hydrogen nuclei (protons) into one helium (Helium-4) nucleus and thereby generates energy in the stellar core. First, two protons (Helium-1) combine to form a deuterium nucleus (Helium-2) with the emission of a positron and a neutrino. The deuterium nucleus then rapidly captures another proton to form a Helium-3 nucleus, while emitting a gamma ray. There are three alternatives for the next step. In the proton-proton chain, occurring in 86% of the cases, two Helium-3 nuclei fuse to a final Helium-4 nucleus while two protons are released. The mass of the resulting Helium-4 nucleus is less than the total mass of the four original protons. The difference, ~ 0.7% of the total mass of the protons, is converted into energy and radiated by the Sun. In this process, the Sun loses some 4 million tons of its mass each second.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T17:06:21.627Z
modified: 2020-11-02T17:06:37.110Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T17:06:37.077Z
  creator: AAS Frey.Katie Admin

Hydrogen deficient stars
type: Concept
broader: Chemically peculiar stars
narrower: AM Canum Venaticorum stars

Astrographic catalogs
type: Concept
preferred label: Astrographic catalogues
broader: Catalogs
modified: 2021-08-24T15:43:01.540Z
contributor: AAS Frey.Katie Admin

Hydrosphere
type: Concept
broader: Planetary structure
modified: 2022-06-15T15:56:36.602Z
contributor: AAS Frey.Katie Admin
definition: A term denoting the water portion of a planet's surface.
modified: 2022-06-15T15:56:21.882Z
editorial note: Definition Provenance
  comment: Adapted from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2022-06-15T15:56:19.107Z
  creator: AAS Frey.Katie Admin

Hydroxyl masers
type: Concept
alternative label: OH masers
broader: Astrophysical masers
related: Hydroxyl sources
definition: A maser phenomenon created by OH molecules with characteristic OH lines. OH masers are detected toward a variety of astronomical environments, including massive star formation regions and evolved late-type stars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:20:44.594Z
modified: 2020-11-04T21:20:57.470Z
editorial note: Definition Provenance
  created: 2020-11-04T21:20:57.437Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Hydroxyl sources
type: Concept
alternative label: OH sources
broader: Astronomical radiation sources
related: OH/IR stars
related: Cocoon stars
related: Hydroxyl masers
definition: An astronomical source emitting microwave radiation characteristic of the hydroxyl OH molecule, especially one showing a maser effect. OH sources are found in molecular clouds in interstellar medium and in the cool envelopes of evolved stars.
modified: 2020-11-04T21:21:42.922Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-04T21:21:56.031Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T21:21:55.997Z

Hyperbolic orbit
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
definition: An orbit that is an open curve whose ends get wider apart at any rate between that of an ellipse and a straight line. Some comets' orbits become hyperbolic through the gravitational influence of a planet the comet passes near.
modified: 2020-11-09T16:54:02.370Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:54:12.206Z
  creator: AAS Frey.Katie
modified: 2020-11-09T16:54:12.237Z

Hypergiant stars
type: Concept
broader: Evolved stars
narrower: Yellow hypergiant stars
contributor: AAS Frey.Katie Admin
definition: A high luminosity star with absolute visual magnitude around -10, about 10^6 times as luminous as the Sun. Hypergiant stars are evolved massive stars belonging to the luminosity class Ia+ or Ia0. Their spectra show very broadened emission and absorption lines resulting from the high luminosity and low surface gravity which favor strong stellar wind.
modified: 2020-11-02T19:20:51.262Z
modified: 2020-11-02T19:21:05.430Z
editorial note: Definition Provenance
  created: 2020-11-02T19:21:05.402Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Hypernovae
type: Concept
alternative label: Hypernova
broader: Supernovae
definition: A highly energetic supernova explosion. This phenomenon, which is more violent than a typical supernova event, is accompanied by a gamma-ray burst.
modified: 2020-11-02T19:21:57.087Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T19:22:10.184Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T19:22:10.157Z

Hypervelocity stars
type: Concept
broader: High-velocity stars
contributor: AAS Frey.Katie Admin
definition: A star whose velocity is so great that it will escape the gravitational potential of our Galaxy. Depending on the location and direction of motion, this criterion typically corresponds to a stellar velocity in the Galactic rest frame larger than 400 km s^-1, and up to about 1200 km s^-1. The nature of the hypervelocity stars (HVSs) spans a wide range of types from OB stars, to metal-poor F-type stars and G/K dwarfs. While there is evidence from many late-type B HVSs in the halo to originate from the Galactic supermassive black hole (SMBH), other HVSs seem to originate from the galactic disk. HVSs can obtain their large velocities from a number of different processes: 1) Tidal disruption of close binary stars by the central SMBH of the Milky Way. In this process one star is captured by the SMBH while the other is ejected at high speed via the gravitational slingshot mechanism. 2) Exchange encounters in other dense stellar environments between hard binaries and massive stars may cause stars to be ejected and escape our Galaxy. 3) Disruption of close binaries via supernova explosions. The runaway velocities of both ejected stars can reach large values when asymmetric supernovae are considered, i.e. when the newborn neutron star receives a momentum kick at birth.
modified: 2020-11-24T19:33:56.776Z
modified: 2020-11-02T19:24:23.145Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T19:24:23.120Z
  creator: AAS Frey.Katie Admin

Hz Herculis x-ray binary stars
type: Concept
broader: Low-mass x-ray binary stars
contributor: AAS Frey.Katie
alternative label: Hz Herculis x-ray binaries
modified: 2019-12-13T21:25:22.394Z

Impact phenomena
type: Concept
related: Meteorites
related: Lunar impacts
contributor: AAS Frey.Katie Admin
narrower: Craters
narrower: Impact gardening
broader: Planetary surfaces
modified: 2022-06-21T17:54:09.432Z

Inclination
type: Concept
broader: Orbital elements
contributor: AAS Frey.Katie
definition: An orbital element that defines the angle between the orbital plane of a solar system body (planet, comet, asteroid) and the plane of the ecliptic.
modified: 2020-11-09T16:56:56.619Z
editorial note: Definition Provenance
  created: 2020-11-09T16:57:07.901Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-09T16:57:07.932Z

Indochinites
type: Concept
broader: Tektites

Inflationary universe
type: Concept
broader: Cosmological models
broader: Early universe
definition: A class of Big Bang models of the Universe that include a finite period of accelerated expansion in their early histories. Such an event would have released enormous energy, stored until then in the vacuum of space-time. The horizon of the Universe expanded, temporarily, much faster than the speed of light.
contributor: AAS Frey.Katie Admin
modified: 2020-11-02T19:40:24.312Z
modified: 2020-11-02T19:40:38.437Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T19:40:38.404Z

Infrared Astronomical Satellite
type: Concept
alternative label: IRAS
broader: Space observatories
broader: Infrared observatories

Infrared astronomy
type: Concept
broader: Astronomical methods
narrower: Near infrared astronomy
narrower: Far infrared astronomy
narrower: Infrared excess
related: Infrared sources
definition: The study of infrared properties of astronomical objects. Infrared is the invisible part of electromagnetic spectrum possessing wavelengths between those of visible light and those of radio waves, i.e. approximately between about 0.75 and 1000 μm.
modified: 2024-06-20T12:21:09.636Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-09T16:58:12.767Z
editorial note: Definition Provenance
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2024-06-20T12:22:01.397Z
modified: 2024-06-20T12:22:01.410Z

Infrared dark clouds
type: Concept
broader: Molecular clouds
broader: Dark interstellar clouds
alternative label: IRDC
contributor: AAS Frey.Katie Admin
definition: A dark cloud characterized by a visual extinction A_v ≥ 10^2 mag. Infrared dark clouds are opaque even at 8 μm, and can be seen in silhouette against the bright diffuse mid-infrared emission in the interstellar medium.
modified: 2020-11-02T19:42:01.103Z
modified: 2020-11-02T19:42:14.928Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T19:42:14.896Z

Infrared excess
type: Concept
alternative label: IR excess
alternative label: IR excess stars
broader: Infrared astronomy
contributor: AAS Frey.Katie
definition: Infrared emission from a star in excess of that expected from a blackbody with the temperature corresponding to the temperature of the star.
modified: 2020-11-09T16:59:18.911Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T16:59:29.281Z
modified: 2020-11-09T16:59:29.315Z

Infrared excess galaxies
type: Concept
alternative label: IR excess galaxies
alternative label: IR excess galaxy
alternative label: IR-excess galaxies
alternative label: IR-excess galaxy
alternative label: Infrared excess galaxy
broader: Galaxies
contributor: AAS Frey.Katie
modified: 2020-10-20T18:53:33.493Z

Astrometric binary stars
type: Concept
alternative label: Astrometric binaries
broader: Binary stars
definition: A binary star in which the presence of an unresolved companion is revealed by small oscillations in the movement of the visible component caused by the gravitational influence of the unseen component.
contributor: AAS Frey.Katie
modified: 2020-10-26T18:48:10.743Z
modified: 2020-10-26T18:48:22.015Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T18:48:21.987Z

Infrared galaxies
type: Concept
broader: Starburst galaxies
narrower: Ultraluminous infrared galaxies
narrower: Luminous infrared galaxies
related: Infrared sources
definition: A galaxy that emits most of its energy in the infrared region of the spectrum. Such galaxies are thought to have unusually high rates of star formation and are also described as starburst galaxies.
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T21:06:03.354Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T19:43:03.072Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-02T19:43:03.101Z

Infrared observatories
type: Concept
broader: Observatories
narrower: Infrared Astronomical Satellite
narrower: James Webb Space Telescope
modified: 2022-06-15T19:27:23.532Z
contributor: AAS Frey.Katie Admin

Infrared photometry
type: Concept
broader: Waveband photometry
related: Medium band photometry
related: Broad band photometry

Infrared telescopes
type: Concept
alternative label: IR telescopes
broader: Space telescopes
definition: A telescope capable of observing infrared radiation from astronomical objects.
modified: 2020-11-02T19:43:34.370Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-02T19:43:47.791Z
modified: 2020-11-02T19:43:47.828Z

Initial conditions of the universe
type: Concept
broader: Early universe

Initial mass function
type: Concept
broader: Stellar evolution

Solar system terrestrial planets
type: Concept
alternative label: Terrestrial planet
broader: Solar system planets
narrower: Mars
narrower: Mercury (planet)
narrower: Venus
narrower: Earth (planet)
alternative label: Terrestrial planets
contributor: AAS Frey.Katie Admin
alternative label: Inner planets
definition: The planets Mercury, Venus, Earth and Mars collectively. They are also known as the terrestrial planets.
related: Extrasolar rocky planets
modified: 2020-11-09T21:34:23.823Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-09T21:25:04.065Z
modified: 2020-11-09T21:25:04.102Z

Instability strip
type: Concept
broader: Hertzsprung Russell diagram
contributor: AAS Frey.Katie
modified: 2020-11-10T17:36:44.703Z
definition: A narrow, almost vertical, band on the right hand side of the main sequence in the H-R diagram occupied by many different types of pulsating stars (RR Lyrae, Cepheids, W Virginis, ZZ Ceti). Stars traverse this region at least once after they leave the main sequence. The narrow temperature range of the instability strip corresponds to the stellar effective temperature that can sustain partial ionization zones, capable of maintaining stellar oscillations. The blue (hot) edge of the instability strip pertains to stars with surface temperatures hotter than ~7500 K. Because these stars have partial ionization zones too close to their surface, the pulsation mechanism is not active. The red (cooler) edge of the instability strip is determined by stars with a temperature lower than ~5500 K. In these stars convection prevents the build-up of heat pressure necessary to drive pulsations.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T17:36:55.705Z
modified: 2020-11-10T17:36:55.736Z

Astronomical instrumentation
type: Concept
alternative label: Equipment and apparatus
broader: Observational astronomy
narrower: Observatories
narrower: Polarimeters
narrower: Solar instruments
narrower: Space vehicles
narrower: Spectrometers
narrower: Stellar tracking devices
narrower: Telescopes
narrower: Transit instruments
narrower: Early astronomical instruments
narrower: High altitude balloons
narrower: Interferometers
narrower: Astronomical detectors
alternative label: Instrumentation
contributor: AAS Frey.Katie
narrower: Photometer
definition: The design and use of scientific instruments for detection, measurement, control, computation, and so on to observe and study astronomical objects.
modified: 2020-10-26T18:52:32.926Z
narrower: Binoculars
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:52:44.503Z
modified: 2020-10-26T18:52:44.527Z

A supergiant stars
type: Concept
alternative label: A supergiants
broader: Early-type supergiant stars
broader: A stars
alternative label: A-type supergiants
related: Alpha Cygni variable stars
alternative label: A-type supergiant stars
modified: 2020-12-17T16:40:45.952Z
contributor: AAS Frey.Katie Admin

Astrometry
type: Concept
broader: Astronomical techniques
narrower: Parallax
narrower: Phase angle
narrower: Phase defect
narrower: Phase effect
narrower: Phase error
narrower: Photographic astrometry
narrower: Baade-Wesselink method
narrower: Radial velocity
narrower: Radio astrometry
narrower: Relativistic aberration
narrower: Relaxation time
narrower: Sky noise
narrower: Solar constant
narrower: Space astrometry
narrower: Spectral index
narrower: Standard stars
narrower: Stellar distance
narrower: Syzygy
narrower: Two-color diagrams
narrower: Bolometric correction
narrower: Wolf diagram
narrower: Brightness temperature
narrower: Distance measure
narrower: Effective temperature
narrower: Equator position
narrower: Fundamental parameters of stars
narrower: Astronomical coordinate systems
narrower: Astronomical location
narrower: Magnitude
related: Astrometric exoplanet detection
definition: The precise measurement of the positions and motions of astronomical objects.
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:22:40.625Z
narrower: Stellar aberration
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:28:20.887Z
modified: 2020-11-03T18:28:20.913Z

Integrated magnitude
type: Concept
alternative label: Total magnitude
broader: Magnitude
contributor: AAS Frey.Katie
definition: The magnitude an extended object (nebula, galaxy, etc.) would have if all of its light were concentrated into a point source.
modified: 2020-11-10T17:37:37.099Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T17:37:47.982Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T17:37:48.020Z

Interacting galaxies
type: Concept
alternative label: Colliding galaxies
broader: Galaxies
narrower: Galaxy collisions
narrower: Galaxy mergers
narrower: Galaxy pairs
narrower: Galaxy tides
narrower: Galaxy triplets
contributor: AAS Frey.Katie
definition: Galaxies that are close enough for their mutual gravitational attraction to produce perturbed shapes or extruded filaments of stellar material, called tidal tails. Most galaxies are in clusters, and gravitational interactions between them are common.
modified: 2020-11-10T17:38:23.253Z
modified: 2020-11-10T17:38:35.631Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T17:38:35.599Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Intercloud medium
type: Concept
alternative label: Intercloud gas
broader: Interstellar medium
contributor: AAS Frey.Katie
definition: A medium in which several molecular clouds are situated.
modified: 2020-11-10T17:39:07.705Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T17:39:18.014Z
modified: 2020-11-10T17:39:18.040Z

Interdisciplinary astronomy
type: Concept
narrower: Astrophysical fluid dynamics
narrower: Philosophy of astronomy
narrower: Astrobiology
top concept of: The Unified Astronomy Thesaurus
narrower: Astrostatistics
contributor: AAS Frey.Katie Admin
narrower: Computational astronomy
narrower: Astrochemistry
narrower: Astroinformatics
narrower: Laboratory astrophysics
narrower: History of astronomy
narrower: Astronomy education
narrower: Cultural astronomy
modified: 2022-06-24T17:25:33.923Z

Interferometers
type: Concept
alternative label: Interferometric instrumentation
alternative label: Interferometric instruments
broader: Astronomical instrumentation
narrower: Michelson interferometers
narrower: Fabry-Perot interferometers
narrower: Mach-Zehnder interferometers
related: Interferometry
modified: 2022-01-05T16:53:00.353Z
contributor: AAS Frey.Katie Admin
definition: An arrangement of two or more separate telescopes placed at some distance from one another, each one receiving electromagnetic radiation (optical, infrared, or radio) from a celestial object and brought together to form an interference pattern.
modified: 2020-11-02T19:44:55.855Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-02T19:44:55.827Z
  creator: AAS Frey.Katie Admin

Interferometric binary stars
type: Concept
alternative label: Interferometric binaries
broader: Binary stars

Interferometric correlation
type: Concept
broader: Interferometry

Interferometry
type: Concept
broader: Astronomical techniques
narrower: Neutron interferometry
narrower: Nonclassical interferometry
narrower: Optical interferometry
narrower: Atomic interferometry
narrower: Phase switching
narrower: Radio interferometry
narrower: Speckle interferometry
narrower: Visibility function
narrower: Adaptive interferometry
narrower: Direct detection interferometry
narrower: Aperture synthesis
narrower: Heterodyne interferometry
narrower: Holographic interferometry
narrower: Interferometric correlation
narrower: Laser interferometry
narrower: Long baseline interferometry
related: Interferometers
definition: An observational technique that uses the interference phenomenon to substantially increase the resolving power of telescopes.
modified: 2020-11-24T17:19:36.037Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T17:19:47.220Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-24T17:19:47.185Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Intergalactic clouds
type: Concept
broader: Intergalactic medium
narrower: Metal line absorbers
narrower: Damped Lyman-alpha systems
narrower: Intergalactic dust clouds
narrower: Lyman-alpha forest clouds
narrower: Lyman limit systems
definition: Intergalactic matter in the form of clouds.
modified: 2020-11-03T16:03:53.510Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:04:06.790Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:04:06.762Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Astronomers
type: Concept
broader: Astronomical research
definition: A person who practices astronomy as a profession rather than as a hobby, in contrast to an amateur astronomer.
contributor: AAS Frey.Katie
modified: 2020-10-26T18:48:52.682Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:49:30.757Z
  creator: AAS Frey.Katie
modified: 2020-10-26T18:49:30.783Z

Intergalactic dust clouds
type: Concept
broader: Intergalactic clouds

Intergalactic filaments
type: Concept
broader: Intergalactic medium

Intergalactic gas
type: Concept
broader: Intergalactic medium

Intergalactic medium
type: Concept
alternative label: IGM
alternative label: Intergalactic matter
broader: Extragalactic astronomy
narrower: Missing mass
narrower: Quasar absorption line spectroscopy
narrower: Dark matter
narrower: Intergalactic clouds
narrower: Intergalactic filaments
narrower: Intergalactic gas
narrower: Intergalactic medium phases
contributor: AAS Frey.Katie
related: Astrophysical dust processes
related: Intracluster medium
narrower: Voids
definition: The matter or environment between the galaxies of a cluster.
modified: 2020-11-10T17:41:05.107Z
modified: 2020-11-10T17:41:15.920Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T17:41:15.891Z

Intergalactic medium phases
type: Concept
broader: Intergalactic medium
narrower: Warm-hot intergalactic medium
narrower: Cool intergalactic medium
narrower: Hot intergalactic medium

Intermediate-mass black holes
type: Concept
broader: Astrophysical black holes

Internal waves
type: Concept
broader: Astrophysical fluid dynamics

Astronomical coordinate systems
type: Concept
alternative label: Celestial coordinate systems
alternative label: Celestial reference system
broader: Astrometry
narrower: Supergalactic coordinate system
narrower: Ecliptic coordinate system
narrower: Equatorial coordinate system
narrower: Galactic coordinate system
narrower: Horizontal coordinate system
definition: Values in a reference system used to relate the position of a body on the celestial sphere. Four main coordinate systems are utilized in astronomy: the equatorial, horizontal, ecliptic, and galactic coordinates systems.
modified: 2020-10-26T18:50:05.412Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:50:17.119Z
modified: 2020-10-26T18:50:17.147Z

Interplanetary discontinuities
type: Concept
broader: Interplanetary physics

Interplanetary dust
type: Concept
alternative label: Interplanetary dust clouds
broader: Interplanetary medium
narrower: Meteoroid dust clouds
narrower: Zodiacal cloud
contributor: AAS Frey.Katie
definition: Particles of dust in the interplanetary medium. They are left-overs from the beginning of the solar system or from other sources such as sublimating comets. Their existence was first deduced from observations of zodiacal light.
modified: 2020-11-10T17:41:51.857Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T17:42:01.592Z
modified: 2020-11-10T17:42:01.618Z

Interplanetary gas
type: Concept
broader: Interplanetary medium
contributor: AAS Frey.Katie
definition: Electrically charged particles of the solar wind and gas liberated from comets within the solar system.
modified: 2020-11-10T17:42:31.611Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T17:42:41.901Z
modified: 2020-11-10T17:42:41.931Z

Interplanetary grains
type: Concept
broader: Interplanetary medium

Interplanetary magnetic fields
type: Concept
broader: Planetary science
related: Interplanetary physics
definition: The magnetic field that is carried along with the solar wind and fills the solar system space. It is wound into a spiral structure by the rotation of the Sun. At the Earth's distance from the Sun, it has a strength of about 5 x 10^-5 gauss.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:06:26.504Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:06:41.092Z
modified: 2020-11-03T16:06:41.122Z

Interplanetary medium
type: Concept
alternative label: Interplanetary material
alternative label: Interplanetary matter
broader: Solar system
narrower: Protoplanetary disks
narrower: Interplanetary dust
narrower: Interplanetary gas
narrower: Interplanetary grains
related: Comets
related: Asteroids
contributor: AAS Frey.Katie
definition: The material contained in the solar system in the space through which the planets travel. It consists of the smaller objects such as asteroids, comets, meteorites and also a general pervading interplanetary dust. Moreover a plasma of charged particles streaming outward from the Sun in the form of the solar wind contributes to the interplanetary medium.
modified: 2020-11-10T17:44:14.360Z
modified: 2020-11-10T17:44:29.220Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T17:44:29.186Z

Interplanetary particle acceleration
type: Concept
broader: Interplanetary physics

Interplanetary physics
type: Concept
broader: Planetary science
narrower: Pickup ions
narrower: Planetary bow shocks
narrower: Solar energetic particles
narrower: Solar wind termination
contributor: AAS Frey.Katie
narrower: Corotating streams
narrower: Interplanetary discontinuities
narrower: Interplanetary particle acceleration
narrower: Interplanetary shocks
narrower: Interplanetary turbulence
related: Solar wind
related: Interplanetary magnetic fields
modified: 2019-12-11T20:50:50.206Z

Interplanetary scintillation
type: Concept
broader: Radio astronomy
broader: Astronomical optics

Astronomy databases
type: Concept
broader: Astronomical reference materials
alternative label: Astronomical databases
broader: Computational methods
contributor: AAS Frey.Katie
broader: Astronomy data analysis
definition: A combined and coordinated set of data that supplies astronomy information for a specific purpose in a variety of forms.
modified: 2020-10-26T18:55:18.759Z
modified: 2020-10-26T18:55:32.810Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T18:55:32.782Z

Interplanetary turbulence
type: Concept
broader: Interplanetary physics

Interstellar absorption
type: Concept
broader: Interstellar medium
narrower: Diffuse interstellar bands
narrower: Interstellar dust extinction
narrower: Interstellar line absorption
contributor: AAS Frey.Katie
modified: 2020-11-10T17:45:00.477Z
definition: The absorption of light from stars and other objects by intervening gas and dust in interstellar space.
modified: 2020-11-10T17:45:11.331Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T17:45:11.303Z

Interstellar abundances
type: Concept
broader: Chemical abundances

Interstellar atomic gas
type: Concept
alternative label: Interstellar atoms
broader: Interstellar medium

Interstellar clouds
type: Concept
alternative label: Interstellar globules
broader: Interstellar medium
narrower: Molecular clouds
narrower: Neutral hydrogen clouds
narrower: Plasma clouds
narrower: Dark interstellar clouds
narrower: Dense interstellar clouds
narrower: Diffuse interstellar clouds
narrower: Evaporating gaseous globules
narrower: High-velocity clouds
narrower: Interstellar dust
definition: An aggregation of gas and dust in the interstellar medium containing large quantities of atoms, molecules, and dust. There are several types of interstellar clouds, such as diffuse interstellar clouds, dark clouds, molecular clouds.
modified: 2020-11-03T16:07:38.033Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:07:50.008Z
editorial note: Definition Provenance
  created: 2020-11-03T16:07:49.979Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Interstellar dust
type: Concept
alternative label: Cosmic dust
alternative label: Dust grain
alternative label: Dust grains
alternative label: Interstellar dust clouds
alternative label: Interstellar dust grains
alternative label: Interstellar grains
broader: Interstellar clouds
narrower: Polycyclic aromatic hydrocarbons
narrower: Silicate grains
narrower: Very small grains
narrower: Carbonaceous grains
related: Interstellar dust processes
related: Solid matter physics
related: Interstellar dust extinction
contributor: AAS Frey.Katie
definition: An aggregation of dust grains in the space between stars. Interstellar dust absorbs, scatters, and polarizes the light from distant stars, causing the interstellar extinction. Large dark regions in the plane of the Milky Way and other galaxies are caused by intervening clouds of dust. The conclusive proof for the presence of a general and selective interstellar absorption is due to R. J. Trumpler (1930).
modified: 2020-11-10T17:46:06.676Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T17:46:16.725Z
modified: 2020-11-10T17:46:16.752Z

Interstellar dust extinction
type: Concept
broader: Interstellar absorption
broader: Interstellar scattering
related: Interstellar dust
contributor: AAS Frey.Katie Admin
definition: The dimming of light traveling in the interstellar space due to the combined effects of absorption and scattering by interstellar dust particles. Interstellar extinction increases at shorter (bluer) wavelengths, resulting in interstellar reddening.
modified: 2021-03-30T14:13:48.130Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:09:24.314Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T16:09:24.349Z

Interstellar dynamics
type: Concept
broader: Interstellar medium

Astronomical detectors
type: Concept
broader: Astronomical instrumentation
narrower: Radio receivers
narrower: X-ray detectors
narrower: CMBR detectors
narrower: Cosmic ray detectors
narrower: Dark matter detectors
narrower: Gamma-ray detectors
narrower: Gravitational wave detectors
definition: A device whose main function is detection. Any device or array of electronic sensors connected to a computer, used to detect the passage of a particle or photon; e.g. a charge-coupled device (CCD).
contributor: AAS Frey.Katie
modified: 2020-10-26T18:51:00.864Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:51:13.630Z
modified: 2020-10-26T18:51:13.654Z

Interstellar emissions
type: Concept
alternative label: Interstellar electromagnetic emissions
alternative label: Interstellar infrared emissions
alternative label: Interstellar optical emissions
broader: Interstellar medium
narrower: Dust continuum emission
narrower: Interstellar cyclotron emission
narrower: Interstellar line emission
narrower: Interstellar masers
narrower: Interstellar synchrotron emission
narrower: Interstellar thermal emission
scope note: Covers all interstellar emissions of electromagnetic radiation.
contributor: AAS Frey.Katie Admin
narrower: Radio continuum emission
modified: 2020-12-03T20:53:05.349Z

Interstellar extinction
type: Concept
broader: Extinction
narrower: Reddened stars
narrower: Interstellar reddening
modified: 2021-03-30T14:14:17.118Z
contributor: AAS Frey.Katie Admin
modified: 2022-01-04T22:33:59.150Z

Interstellar filaments
type: Concept
alternative label: Filaments
broader: Interstellar medium
contributor: AAS Frey.Katie
related: Filamentary nebulae
modified: 2019-12-11T15:54:43.913Z

Interstellar line absorption
type: Concept
broader: Interstellar absorption

Interstellar line emission
type: Concept
broader: Interstellar emissions
narrower: CO line emission
narrower: H I line emission
scope note: For interstellar emission lines, besides H1 and CO, use this concept.

Interstellar magnetic fields
type: Concept
broader: Interstellar medium
definition: A large-scale, weak magnetic field, with an estimated strength of about 1 to 5 microgauss, that pervades the disk of the Milky Way Galaxy and controls the alignment of interstellar dust grains.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:09:53.354Z
modified: 2020-11-03T16:10:05.593Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:10:05.569Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Interstellar masers
type: Concept
broader: Interstellar emissions
definition: A maser phenomenon created by young stars and protostars in the surrounding dense molecular clouds of gas and dust.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:10:34.062Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:10:46.620Z
modified: 2020-11-03T16:10:46.647Z

Interstellar medium
type: Concept
alternative label: ISM
alternative label: Interstellar material
alternative label: Interstellar matter
alternative label: Interstellar media
narrower: Astrophysical masers
narrower: Nebulae
narrower: Protostars
narrower: Stellar-interstellar interactions
narrower: Stellar bridges
narrower: Stellar wind bubbles
narrower: Superbubbles
narrower: Supernova remnants
narrower: Tidal tails
narrower: Intercloud medium
narrower: Interstellar absorption
narrower: Interstellar atomic gas
narrower: Interstellar clouds
narrower: Interstellar dynamics
narrower: Interstellar emissions
narrower: Interstellar filaments
narrower: Interstellar magnetic fields
narrower: Interstellar molecules
narrower: Interstellar phases
narrower: Interstellar plasma
narrower: Interstellar radiation field
narrower: Interstellar scattering
top concept of: The Unified Astronomy Thesaurus
contributor: AAS Frey.Katie Admin
definition: The environment containing the interstellar matter (the gas and dust that exists in open space between the stars), consisting of gas (mostly hydrogen) and dust. Even at its densest phase, the interstellar medium is emptier than the best vacuum man can create in the laboratory, but because space is so vast, the interstellar medium still adds up to a huge amount of mass.
modified: 2020-11-03T16:11:41.927Z
editorial note: Definition Provenance
  created: 2020-11-03T16:11:54.321Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:11:54.348Z

Interstellar medium wind
type: Concept
alternative label: Interstellar wind
broader: Stellar-interstellar interactions
modified: 2020-11-24T16:24:12.746Z
scope note: Wind that a star perceives from the ISM.
contributor: AAS Frey.Katie Admin

Interstellar molecules
type: Concept
broader: Interstellar medium
definition: Any molecule that occurs naturally in clouds of gas and dust in the interstellar medium. So far more than 140 species have been discovered, many of which nonexistent on Earth.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:12:11.630Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:12:26.027Z
modified: 2020-11-03T16:12:26.057Z

Astronomical location
type: Concept
broader: Astrometry
narrower: Opposition
narrower: Optical position
narrower: True position
narrower: Conjunction
narrower: Angular separation
narrower: Apparent position
narrower: Line of sight

Interstellar phases
type: Concept
broader: Interstellar medium
narrower: Molecular gas
narrower: Warm ionized medium
narrower: Warm neutral medium
narrower: Cold neutral medium
narrower: Hot ionized medium

Interstellar plasma
type: Concept
alternative label: Highly ionised interstellar gas
alternative label: Highly ionized interstellar gas
alternative label: Interstellar ionized gas
alternative label: Ionised interstellar gas
alternative label: Ionised interstellar gases
alternative label: Ionized interstellar gas
alternative label: Ionized interstellar gases
broader: Interstellar medium

Interstellar radiation field
type: Concept
broader: Interstellar medium
contributor: AAS Frey.Katie
definition: A global ionizing radiation in the interstellar medium provided by various sources all together.
modified: 2020-11-10T17:53:10.506Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T17:53:20.693Z
  creator: AAS Frey.Katie
modified: 2020-11-10T17:53:20.721Z

Interstellar reddening
type: Concept
broader: Interstellar extinction
contributor: AAS Frey.Katie
definition: The dimming of light during its travel in the interstellar medium due to absorption by intervening dust grains. Since shorter wavelengths are particularly affected, the spectrum of the light is increasingly dominated by the long wavelength end of the spectrum. As a result, the light is 'reddened' as it travels through space. Robert J. Trumpler (1886-1956), a Swiss-American astronomer, was the first to produce a definite evidence of the existence of interstellar extinction and to estimate its magnitude (1930).
modified: 2020-11-10T17:54:13.218Z
modified: 2020-11-10T17:54:23.768Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T17:54:23.737Z
  creator: AAS Frey.Katie

Interstellar scattering
type: Concept
broader: Interstellar medium
narrower: Interstellar dust extinction

Interstellar scintillation
type: Concept
broader: Radio astronomy
broader: Astronomical optics
contributor: AAS Frey.Katie
modified: 2020-11-10T17:55:17.947Z
definition: An apparent twinkling of the signals from distant point-like radio sources (pulsars). It is due to turbulence, i.e. fluctuations in the electron density of the interstellar ionized gas, through which the signals have passed on their way to Earth.
modified: 2020-11-10T17:55:27.687Z
editorial note: Definition Provenance
  created: 2020-11-10T17:55:27.656Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Interstellar synchrotron emission
type: Concept
alternative label: Synchrotron emission
broader: Interstellar emissions

Interstellar thermal emission
type: Concept
broader: Interstellar emissions

Intracluster medium
type: Concept
alternative label: ICM
alternative label: Intracluster matter
broader: Galaxy clusters
broader: High energy astrophysics
contributor: AAS Frey.Katie Admin
narrower: Cooling flows
related: Intergalactic medium
definition: A diffuse, hot, magnetized plasma that exists between galaxies in a galaxy cluster and is composed mainly of H, He, and heavy elements. The Intracluster medium (ICM) strongly emits X-rays, making it the most luminous extended X-ray source in Universe. While some of the gas has been stripped out of galaxies, it is also likely that some is also primordial in nature, and has been accreted into the clusters. The origin of the ICM is subject of intense investigation. Broadly, two possibilities have been envisaged. The first one considers the intracluster gas to be once contained in galaxies and later driven in the ICM. This would explain several observations: the presence of high metallicity gas, and H I deficiency of galaxies residing in the cores of rich clusters (which suggests that gas stripping has occurred). Alternatively, the ICM is primordial, originating at the time of cluster formation. Actually the ICM may result from a combination of both scenarios.
modified: 2020-11-03T16:13:51.037Z
modified: 2020-11-03T16:14:05.777Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:14:05.749Z
  creator: AAS Frey.Katie Admin

Intrinsic variable stars
type: Concept
alternative label: Unstable stars
broader: Variable stars
narrower: Pulsating variable stars
narrower: Cataclysmic variable stars
narrower: Eruptive variable stars
narrower: Herbig-Haro objects
narrower: Magnetic variable stars
contributor: AAS Frey.Katie Admin
definition: A variable star whose fluctuations in brightness are due to natural changes in the luminosity of the star itself, not by external causes, such as in extrinsic variable stars.
modified: 2020-12-03T20:33:15.429Z
modified: 2020-11-03T16:14:52.721Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:14:52.691Z

Earth ionosphere
type: Concept
broader: Earth atmosphere
narrower: D layer
narrower: E layer
related: Ionospheric scintillation
narrower: F layer
definition: The region of the Earth's upper atmosphere containing a small percentage of free electrons and ions produced by photoionization of the constituents of the atmosphere by solar ultraviolet radiation.
contributor: AAS Frey.Katie Admin
modified: 2020-12-09T19:19:15.838Z
alternative label: Earth's ionosphere
contributor: AAS Frey.Katie
modified: 2020-11-10T17:57:47.303Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T17:57:47.260Z

Ionospheric scintillation
type: Concept
broader: Atmospheric scintillation
related: Earth ionosphere

Iron meteorites
type: Concept
broader: Meteorites
definition: A meteorite which is composed mainly of iron mixed with smaller amounts of nickel. Iron meteorites make up about 4.4% of all meteorites.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T16:01:38.117Z
modified: 2020-11-05T16:01:52.966Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-05T16:01:52.931Z

Irregular galaxies
type: Concept
broader: Galaxies
narrower: Amorphous irregular galaxies
narrower: Dwarf irregular galaxies
related: De Vaucouleurs Sandage classification
related: Hubble classification scheme
contributor: AAS Frey.Katie Admin
narrower: Magellanic irregular galaxies
definition: A galaxy with no spiral structure and no symmetric shape. Irregular galaxies are usually filamentary or very clumpy in shape and tend to smaller than others. Two types of irregular galaxies are defined, Irr I galaxy and Irr II galaxy.
modified: 2020-12-16T15:48:51.789Z
editorial note: Definition Provenance
  created: 2020-11-03T16:17:47.757Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:17:47.785Z

Magellanic Clouds
contributor: AAS Frey.Katie
type: Concept
alternative label: Nubeculae Magellani
broader: Local Group
narrower: Small Magellanic Cloud
narrower: Large Magellanic Cloud
narrower: Magellanic Stream
related: Milky Way Galaxy
definition: Two irregular satellite galaxies of our own Galaxy which are visible from the Southern Hemisphere as misty patches in the night sky.
modified: 2020-11-10T18:56:14.758Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:56:24.390Z
modified: 2020-11-10T18:56:24.419Z

Irregular variable stars
type: Concept
broader: Pulsating variable stars
broader: Late-type giant stars
narrower: R Coronae Borealis variable stars
narrower: Soft gamma-ray repeaters
narrower: T Tauri stars
narrower: Lc variable stars
contributor: AAS Frey.Katie Admin
definition: A type of variable star in which variations in brightness show no regular periodicity. There are two main types, irregular eruptive variables and irregular pulsating variables.
example: Aldebaran
modified: 2022-06-24T15:24:54.423Z
editorial note: Definition Provenance
  created: 2020-11-03T16:20:24.436Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:20:24.467Z

Isothermal sphere profile
type: Concept
broader: Large-scale structure of the universe

Jeans mass
type: Concept
broader: Gravitational collapse
definition: The minimum mass for an interstellar cloud below which the thermal pressure of the gas prevents its collapse under the force of its own gravity. High density favors collapse, while high temperature favors larger Jeans mass.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:36:11.796Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:01:35.937Z
  creator: AAS Frey.Katie
modified: 2020-11-10T18:01:35.968Z
contributor: AAS Frey.Katie

Astronomical object identification
type: Concept
broader: Astronomical techniques

Jets
type: Concept
broader: High energy astrophysics
narrower: Plasma jets
narrower: Radio jets
narrower: Stellar jets
narrower: Galaxy jets
contributor: AAS Frey.Katie Admin
definition: Fountain-like formations of gas and/or dust gushing out from compact regions of some astronomical objects.
modified: 2020-11-03T16:23:46.050Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:23:57.255Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:23:57.282Z

Johnson photometry
type: Concept
alternative label: Johnson-Morgan filter system
alternative label: Three-color photometry
alternative label: UBV RI jkl photometry
alternative label: UBV RI photometry
alternative label: UBV photometry
broader: Broad band photometry

Jovian satellites
type: Concept
alternative label: Jovian moons
alternative label: Moons of Jupiter
broader: Natural satellites (Solar system)
narrower: Galilean satellites
contributor: AAS Frey.Katie Admin
alternative label: Classical satellites
related: Jupiter
alternative label: Jupiter's satellites
alternative label: Jupiter's moons
modified: 2020-12-09T15:24:58.093Z
example: Leda
example: Thebe
example: Amalthea

Jupiter
type: Concept
broader: Solar system gas giant planets
related: Jovian satellites
contributor: AAS Frey.Katie Admin
definition: The largest planet in the Solar System and the fifth from the Sun, lying at a mean distance of about 5.2 astronomical units from the Sun. Jupiter is a gas giant, mostly hydrogen and helium, with a mass of 1.898 x 10^27 kg, or about 0.001 solar masses, or 318 times Earth masses. It is more than twice as massive as all the other solar system planets combined. Jupiter's diameter measures 11 times that of Earth. Its rotation period, 9.93 hours (Jupiter/Earth ratio = 0.41), is the shortest of all the solar system planets. Its orbital period is 11.857 Earth years. Jupiter has an extensive family of satellites (79 known) and a faint ring system; Jupiter's ring. Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth masses. Above the core lies the main bulk of the planet in the form of liquid metallic hydrogen. This exotic form of the most common of elements is possible only at pressures about 3 million bars, as is the case in the interior of Jupiter (and Saturn). Under the extreme pressure found deep inside Jupiter, the electrons are released from the hydrogen molecules and are free to move about the interior. This causes hydrogen to behave as a metal; it becomes conducting for both heat and electricity.
modified: 2020-11-24T17:10:30.752Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T18:03:31.421Z
modified: 2020-11-10T18:03:31.454Z

Jupiter trojans
type: Concept
broader: Trojan asteroids
modified: 2020-11-10T18:04:04.018Z
contributor: AAS Frey.Katie
definition: The family of asteroids that share Jupiter's orbit and lie in elongated, curved regions around the two Lagrangian points 60° ahead and behind of Jupiter. The Lagrangian points L4 and L5 host several thousands of them.
modified: 2020-11-10T18:04:18.464Z
editorial note: Definition Provenance
  created: 2020-11-10T18:04:18.417Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie

Stellar K corona
type: Concept
broader: Stellar coronae
related: Solar K corona
contributor: AAS Frey.Katie
alternative label: Stellar K coronal regions
modified: 2019-11-26T18:05:28.644Z

K giant stars
type: Concept
alternative label: K giants
broader: K stars
broader: Late-type giant stars
alternative label: K-type giant stars
alternative label: K-type giants
example: Aldebaran
contributor: AAS Frey.Katie Admin
example: Arcturus
modified: 2022-06-24T15:26:14.921Z

K stars
type: Concept
alternative label: Class K stars
contributor: AAS Frey.Katie Admin
alternative label: K-type stars
broader: Late-type stars
narrower: K dwarf stars
narrower: K giant stars
narrower: K subdwarf stars
narrower: K subgiant stars
narrower: K supergiant stars
related: Stellar classification
broader: Stellar spectral types
definition: An orange-red star of spectral type K with a surface temperature of about 3600-5000 K. The spectra of K stars are dominated by the H and K lines of calcium and lines of neutral iron and titanium, with molecular bands due to cyanogen (CN) and titanium dioxide (TiO). Examples are Arcturus and Aldebaran.
modified: 2020-11-03T16:24:45.841Z
editorial note: Definition Provenance
  created: 2020-11-03T16:25:00.431Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:25:00.459Z

Astronomical optics
type: Concept
broader: Astronomical techniques
narrower: Atmospheric refraction
narrower: Atmospheric scintillation
narrower: Stellar atmospheric opacity
narrower: Collimation
narrower: Dark adaption
narrower: Extinction
narrower: Interplanetary scintillation
narrower: Interstellar scintillation
narrower: Laser guide stars
narrower: Astronomical seeing
narrower: Adaptive optics
narrower: Optical aberration
narrower: Optical filters

Kappa mechanism
type: Concept
alternative label: K mechanism
alternative label: K-mechanism
broader: Luminosity classification
related: Variable stars
contributor: AAS Frey.Katie
alternative label: κ-mechanism
modified: 2020-11-10T18:05:28.173Z
definition: A process based on the effects of opacity (κ) that drives the pulsations of many types of variable stars. Consider a layer of material within a star and suppose that it undergoes inward contraction. This inward motion tends to compress the layer and increase the density. Therefore the layer becomes more opaque. If a certain amount of flux comes from the deeper layers it gets stuck in the high κ region. The energy accumulates and heat builds up beneath it. The pressure rises below the layer, pushing it outward. The layer expands as it moves outward, cools and becomes more transparent to radiation. Energy can now escape from below the layer, and pressure beneath the layer diminishes. The layer falls inward and the cycle repeats. The κ mechanism is believed to account for the pulsations of several star families, including Delta Scuti stars, Beta Cephei variables, Cepheids, and RR Lyrae stars.
editorial note: Definition Provenance
  created: 2020-11-10T18:05:38.826Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T18:05:38.857Z

Kapteyn Selected Areas
type: Concept
alternative label: Kapteyn's Selected Areas
broader: Surveys

Keplerian orbit
type: Concept
broader: Orbital motion
contributor: AAS Frey.Katie
definition: The orbit of a spherical object of a finite mass around another spherical object, also of finite mass, governed by their mutual gravitational forces only.
modified: 2020-11-10T18:06:05.101Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T18:06:15.081Z
modified: 2020-11-10T18:06:15.111Z

Kerr-Newman black holes
type: Concept
broader: Rotating black holes
broader: Charged black holes
definition: A rotating charged black hole. Compare with the Kerr black hole and the Reissner-Nordstrom black hole.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:27:00.675Z
modified: 2020-11-03T16:27:15.593Z
editorial note: Definition Provenance
  created: 2020-11-03T16:27:15.556Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Kerr black holes
type: Concept
broader: Rotating black holes
broader: Uncharged black holes
narrower: Maximal Kerr black holes
related: Ring singularities
related: Wormholes
definition: A black hole that possesses only mass (not electric charge) and rotates about a central axis. It has an ergosphere and a stationary limit.
modified: 2020-11-03T16:26:14.632Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:26:25.921Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:26:25.894Z
  creator: AAS Frey.Katie Admin

Kerr metric
type: Concept
broader: Spacetime metric

Kinematic parallax
type: Concept
broader: Parallax

Kirkwood gaps
type: Concept
broader: Orbital resonances
contributor: AAS Frey.Katie Admin
alternative label: Kirkwood gap
modified: 2020-11-03T16:27:55.240Z
definition: Regions in the asteroid belt within which few asteroids are found. The Kirkwood gaps are due to the perturbing effects of Jupiter through resonances with Jupiter's orbital period.
modified: 2020-11-03T16:28:28.969Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:28:28.940Z

Astronomical radiation sources
type: Concept
alternative label: Cosmic radiation sources
broader: Cosmology
narrower: Non-thermal radiation sources
narrower: Radio sources
narrower: Ultraviolet sources
narrower: Variable radiation sources
narrower: X-ray sources
narrower: Compact radiation sources
narrower: Cosmic rays
narrower: Extended radiation sources
narrower: Extrasolar radiation
narrower: Gamma-ray sources
narrower: Hydroxyl sources
narrower: Infrared sources
narrower: Visible sources

Kreutz group
type: Concept
broader: Sungrazers
contributor: AAS Frey.Katie Admin
alternative label: Kreutz sungrazers
modified: 2020-12-04T18:48:18.940Z

Kron-Cousins photometry
type: Concept
alternative label: Kron cousins photometry
alternative label: Kron-Cousins RI photometry
broader: Broad band photometry

Kruskal diagram
type: Concept
alternative label: Kruskal-Szekeres diagram
broader: Black hole physics
contributor: AAS Frey.Katie
modified: 2020-11-10T18:10:10.646Z
definition: A diagram used to plot trajectories in space-time near a black hole. The vertical and horizontal axes are two complicated functions of time and distance from the black hole. Lines of constant time radiate from the origin of the diagram, with steeper slopes corresponding to later times. Lines of constant distance are hyperbolas, lines of constant time pass through the origin; photons always travel along diagonal lines at ±45° to the vertical. The trajectory of an object falling into the black hole is shown as a curving line moving upward on the diagram at less than 45° to the vertical.
modified: 2020-11-10T18:10:20.916Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T18:10:20.885Z

Kuiper belt
type: Concept
alternative label: Edgeworth-Kuiper belt
alternative label: Edgeworth–Kuiper belt
broader: Solar system
narrower: Trans-Neptunian objects
contributor: AAS Frey.Katie
definition: A region of the Solar System extending roughly from the orbit of Neptune, or 30 astronomical units (AU), to 50 AU from the Sun that contains many small icy bodies. The Kuiper belt is now considered to be the source of the short-period comets.
modified: 2020-11-10T18:10:57.459Z
editorial note: Definition Provenance
  created: 2020-11-10T18:11:07.012Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T18:11:07.091Z

L dwarfs
type: Concept
alternative label: L dwarf stars
broader: Brown dwarfs
broader: Late-type dwarf stars
alternative label: L-type brown dwarfs
alternative label: L brown dwarfs
contributor: AAS Frey.Katie Admin
definition: A type of brown dwarf with an effective temperature ranging from about 2200 K to about 1300 K, corresponding to luminosities about 4 x 10^-4 to 3 x 10^-5 times that of the Sun. L dwarfs are intermediate in temperature between M and T dwarfs. Their spectra in the optical show weak titanium oxide (TiO) and vanadium oxide (VO) absorption lines and strong metallic hydrides CrH (8611 and 9969 Å) and FeH (8692 and 9896 Å). Also are present strong neutral atomic lines of alkali metals Na I (8183, 8195 Å), K I (7665, 7699 Å), Rb I (7800, 7948 Å), Cs I (8521, 8943 Å), and sometimes Li I (6708 Å). The prototype of the L-dwarf class is GD 165B.
preferred label: L dwarves
modified: 2021-09-27T15:41:57.730Z
modified: 2020-11-03T16:30:25.506Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:30:25.478Z

L galaxies
contributor: AAS Frey.Katie
type: Concept
alternative label: L-galaxies
broader: Low surface brightness galaxies
definition: In Morgan's classification, an elongated galaxy of low surface brightness.
modified: 2020-11-10T18:13:26.575Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T18:13:38.059Z
  comment: Glossary of Astronomy and Astrophysics, J. Hopkins, University of Chicago Press (1976)
modified: 2020-11-10T18:13:38.095Z

Lagrangian points
type: Concept
alternative label: L-points
alternative label: Lagrange points
alternative label: Libration points
broader: Three-body problem
definition: Five locations in space where the centrifugal force and the gravitational force of two bodies (m orbiting M) neutralize each other. A third, less massive body, located at any one of these points, will be held in equilibrium with respect to the other two. Three of the points, L1, L2, and L3, lie on a line joining the centers of M and m. L1 lies between M and m, near to m, L2 lies beyond m, and L3 on the other side of M beyond the orbit. The other two points, L4 and L5, which are the most stable, lie on either side of this line, in the orbit of m around M, each of them making an equilateral triangle with M and m. L4 lies in the m's orbit approximately 60° ahead of it, while L5 lies in the m's orbit approximately 60° behind m.
modified: 2020-11-03T16:31:34.631Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:31:47.164Z
modified: 2020-11-03T16:31:47.195Z

Lambda density
type: Concept
broader: Density parameters

Lambda Eridani stars
type: Concept
broader: Pulsating variable stars
broader: Be stars

Abell clusters
type: Concept
broader: Galaxy clusters
contributor: AAS Frey.Katie
definition: Galaxy clusters listed in the Abell catalog, which is a catalog of 4073 rich galaxy clusters grouped by constellation and by catalog number. Published first in 1958, it contained the clusters visible from the northern hemisphere. A supplement for the southern hemisphere survey was published in 1988.
modified: 2020-10-26T18:30:02.022Z
modified: 2020-10-26T18:29:41.488Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:29:41.452Z

Astronomical reference materials
type: Concept
broader: Astronomical research
narrower: Star atlases
narrower: Surveys
narrower: Calendars
narrower: Catalogs
narrower: Almanacs
narrower: Ephemerides
narrower: Finding charts
narrower: Finding lists
narrower: Astronomy databases

Land-atmosphere interactions
type: Concept
alternative label: Land atmosphere interactions
broader: Earth atmosphere

Landers
type: Concept
broader: Space probes
definition: A space probe designed to land on a planet or other solid celestial body.
modified: 2020-11-03T16:33:00.831Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:33:15.240Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T16:33:15.266Z

Large-scale structure of the universe
type: Concept
alternative label: Large scale structure of the cosmos
alternative label: Large scale structure of the universe
alternative label: Large-scale structure of the cosmos
broader: Cosmology
narrower: Mean matter density
narrower: Voids
narrower: Warm-hot intergalactic medium
narrower: Cosmic web
narrower: Dark matter distribution
narrower: Great Attractor
narrower: Isothermal sphere profile
narrower: Low-density fields

Large Magellanic Cloud
type: Concept
alternative label: L m c
broader: Magellanic Clouds
alternative label: LMC
contributor: AAS Frey.Katie Admin
definition: The larger of the two Magellanic Cloud galaxies visible in the southern hemisphere at about 22 degrees from the South Celestial Pole. It is approximately on the border between the constellations Dorado and Mensa in a region of faint stars. The center of the LMC is approximately RA: 5h 23m 35s, dec: -69° 45' 22''. The LMC shines with a total apparent visual magnitude of approximately zero. It spans an area of the sky about 9 by 11 degrees, corresponding to about 30,000 light-years across in the longest dimension, for a distance of some 162,000 light-years. It has a visible mass of about one-tenth that of our own Galaxy (10^10 M_sun). The LMC and its twin, the Small Magellanic Cloud, are two of our most prominent Galactic neighbors. The LMC is classified as a disrupted barred spiral galaxy of type SBm, the prototype of a class of Magellanic spirals. The galaxy is characterized by a prominent offset stellar bar located near its center with the dominant spiral arm to the north with two "embryonic" arms situated to the south. The metallicity in the LMC is known to be lower than in the solar neighborhood by a factor 2 or more. Based on 20 eclipsing binary systems, the distance to the LMC is measured to one percent precision to be 49.59±0.09 (statistical) ±0.54 (systematic) kpc.
modified: 2020-11-03T16:35:12.482Z
modified: 2020-11-03T16:35:30.229Z
editorial note: Definition Provenance
  created: 2020-11-03T16:35:30.203Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Laser guide stars
type: Concept
broader: Astronomical optics

Laser interferometry
type: Concept
broader: Interferometry
narrower: LIGO

Late-type galaxies
type: Concept
alternative label: Late type galaxies
broader: Galaxies
definition: In the Hubble classification, a galaxy on the left part of the Hubble sequence.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:37:09.142Z
modified: 2020-11-03T16:37:22.213Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:37:22.182Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Late-type stars
type: Concept
alternative label: Late type stars
narrower: N stars
narrower: R stars
narrower: S stars
narrower: K stars
narrower: Late-type dwarf stars
narrower: Late-type giant stars
narrower: Late-type supergiant stars
narrower: M stars
alternative label: Cool stars
broader: Stellar types
definition: A star of spectral type K, M, S, or C, with a surface temperature lower than that of the Sun.
modified: 2020-11-03T16:37:44.865Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:37:58.550Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:37:58.519Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Astronomical research
type: Concept
broader: Observational astronomy
narrower: Astrophysicists
narrower: Space research
narrower: Classification systems
narrower: Amateur astronomers
narrower: Astronomers
narrower: Astronomical reference materials
narrower: Astronomical site protection
narrower: Stellar evolutionary models
narrower: Cultural astronomy
contributor: AAS Frey.Katie Admin
modified: 2022-06-24T17:27:55.804Z

Late stellar evolution
type: Concept
broader: Stellar evolution
narrower: Stellar accretion disks
narrower: Dredge-up

Lemaitre universe
type: Concept
alternative label: Lemaître universe
broader: Cosmological models

Lenticular galaxies
type: Concept
alternative label: S0 galaxies
broader: Disk galaxies
related: De Vaucouleurs Sandage classification
related: Hubble classification scheme

Leptogenesis
type: Concept
broader: Early universe

Libration
type: Concept
alternative label: Physical libration
broader: Orbital motion
contributor: AAS Frey.Katie
modified: 2020-11-10T18:16:12.227Z
definition: Small oscillations of a celestial body about its mean position. The term is used mainly to mean the Moon's libration caused by the apparent wobble of the Moon as it orbits the Earth. The Moon always keeps the same side toward the Earth, but due to libration, 59% of the Moon's surface can be seen over a period of time. This results from three kinds of libration working in combination: libration in longitude, libration in latitude, and diurnal libration.
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T18:16:21.977Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T18:16:22.005Z

Light curves
type: Concept
alternative label: Lightcurves
broader: Photometry
related: Light curve classification
definition: A curve showing the behavior of the light from a variable star over a period of time.
modified: 2020-12-11T18:47:12.619Z
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:17:09.864Z
modified: 2020-11-10T18:17:09.890Z

Light year
type: Concept
alternative label: Light-year
alternative label: Lightyear
broader: Distance measure
contributor: AAS Frey.Katie
definition: The distance that light travels in one year at about 300,000 km per second, i.e. 9.5 x 10^12 km. It is equal to about 63,000 astronomical units.
modified: 2020-11-10T18:17:41.600Z
modified: 2020-11-10T18:17:51.761Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:17:51.729Z

Astronomical seeing
type: Concept
alternative label: Dome seeing
broader: Astronomical optics
definition: A measure of the blurring and degradation of the image of astronomical objects caused by turbulence in the Earth's atmosphere, including the telescope environment. Seeing causes the images of stars to break up into speckle patterns, which change very rapidly with time.
modified: 2020-11-05T15:23:48.696Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-05T15:24:01.569Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-05T15:24:01.601Z

LIGO
type: Concept
alternative label: Laser Interferometer Gravitational-Wave Observatory
broader: Laser interferometry
modified: 2020-11-10T18:18:47.803Z
definition: A facility dedicated to the detection and measurement of cosmic gravitational waves. It consists of two widely separated installations, or detectors, within the United States, operated in unison as a single observatory. One installation is located in Hanford (Washington) and the other in Livingston (Louisiana), 3,000 km apart. Funded by the National Science Foundation (NSF), LIGO was designed and constructed by a team of scientists from the California Institute of Technology, the Massachusetts Institute of Technology, and by industrial contractors. Construction of the facilities was completed in 1999. Initial operation of the detectors began in 2001. Each LIGO detector beams laser light down arms 4 km long, which are arranged in the shape of an 'L.' If a gravitational wave passes through the detector system, the distance traveled by the laser beam changes by a minuscule amount -- less than one-thousandth of the size of an atomic nucleus (10^-18 m). Still, LIGO should be able to pick this difference up. LIGO directly detected gravitational waves for the first time from a binary black hole merger (GW150914) on September 14, 2015. The Nobel Prize in physics 2017 was awarded to three physicists (Rainer Weiss, Barry C. Barish, and Kip S. Thorne) for decisive contributions to the LIGO detector and the observation of gravitational waves. LIGO had a prominent role in the detection of GW170817, the first event with an electromagnetic counterpart.
contributor: AAS Frey.Katie
modified: 2020-11-03T16:41:42.105Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T16:41:42.078Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Limb brightening
type: Concept
broader: Solar atmosphere
definition: An observed increase in the intensity of radio, extreme ultraviolet, or X-radiation from the Sun from its center to its limb.
modified: 2020-11-10T18:28:21.027Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  created: 2020-11-10T18:28:34.609Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T18:28:34.639Z

Limb darkening
type: Concept
modified: 2020-11-10T18:29:18.593Z
broader: Solar atmosphere
definition: An apparent decrease in brightness of the Sun near its edge as compared to its brightness toward the center. Limb darkening is readily apparent in photographs of the Sun. The reason is that when we look toward the disk's center we look into deeper and hence hotter layers along the line of sight. Toward the limb, we get radiation from higher and hence cooler and less bright layers of the photosphere. Limb darkening has been detected in the case of several other stars. A similar phenomenon occurs in eclipsing binaries where the effect of limb darkening on one or both components manifests itself in the shape of the system's light curve.
contributor: AAS Frey.Katie
modified: 2020-11-10T18:29:29.245Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:29:29.206Z

Limiting magnitude
type: Concept
broader: Apparent magnitude
contributor: AAS Frey.Katie
definition: The faintest magnitude reachable by an instrument.
modified: 2020-11-10T18:30:04.820Z
modified: 2020-11-10T18:30:16.385Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:30:16.351Z

Line of sight
type: Concept
broader: Astronomical location
contributor: AAS Frey.Katie
definition: The imaginary straight line connecting the object and the objective lens of the viewing device.
modified: 2020-11-10T18:30:44.112Z
modified: 2020-11-10T18:30:53.863Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:30:53.834Z

LINER galaxies
type: Concept
broader: Active galaxies
broader: Emission line galaxies

Lithium stars
type: Concept
alternative label: Li stars
alternative label: Lithium rich stars
alternative label: Lithium-rich stars
broader: Chemically peculiar stars

Lithosphere
type: Concept
broader: Planetary structure
contributor: AAS Frey.Katie
definition: The solid portion of the Earth, as compared to the atmosphere and the hydrosphere. The lithosphere consists of semi-rigid plates that move relative to each other on the underlying asthenosphere. The process is known as plate tectonics and helps explain continental drift.
modified: 2020-11-10T18:32:18.644Z
modified: 2020-11-10T18:32:31.615Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-10T18:32:31.585Z

Local Group
type: Concept
broader: Galaxy groups
narrower: Milky Way Galaxy
narrower: Triangulum Galaxy
narrower: Andromeda Galaxy
narrower: Magellanic Clouds
modified: 2020-11-24T17:14:05.371Z
definition: A small galaxy cluster of about 50 galaxies to which our Milky Way galaxy belongs. The Local Group occupies a volume of space nearly 10 million light-years across centered somewhere between the Andromeda Galaxy (M31) and the Milky Way, which are the dominant galaxies of the group; Andromeda being the principal member. Both of these galaxies exhibit spiral structures, and each is attended by a large family of satellite dwarf galaxies. The Local Group also includes a third spiral galaxy known as Triangulum (M33), which is bound to Andromeda. The remaining members span a range of Hubble classification types from dwarf spheroidal to Irr to Sb and Sc and cover a factor of 10 in metallicity. The total mass of the Local Group is estimated to be about 2 x 10^12 solar masses, although this value is still uncertain to within a factor of about 2. The velocities of the individual galaxies of the Local Group are not particularly high. Therefore no member is believed to be able to escape the group, which is thus considered to be gravitationally bound. Another remarkable member of the Group is IC 10.
contributor: AAS Frey.Katie Admin
modified: 2020-11-10T18:33:20.626Z
contributor: AAS Frey.Katie
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:33:20.589Z
  creator: AAS Frey.Katie

Astronomical sextants
type: Concept
alternative label: Astronomer's sextants
alternative label: Framed sextants
alternative label: Mural sextants
broader: Early astronomical instruments
definition: An instrument used mainly in nautical astronomy to determine the angular distances of celestial bodies above the horizon. The sextant consists of a 60° graduated arc, or limb, a small telescope, and two mirrors. Only half of one of the mirrors, the horizon glass, is silvered and, like the telescope, it is fastened to the frame supporting the limb. The other mirror, the index mirror, moves with an index arm pivoted at the center of the arc. The index arm is equipped with a vernier which moves along the limb. An object in direction S can be observed in the telescope through the un-silvered portion of the horizon glass. By moving the index arm, the second object S' is made to coincide with S in the telescope. According to the law of reflection, the angle between S and S' is double the angle between the mirrors. The angular distance between the objects can therefore be obtained from the measurement of angles between the planes of the mirrors.
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T15:22:59.988Z
modified: 2020-11-05T15:23:17.746Z
editorial note: Definition Provenance
  created: 2020-11-05T15:23:17.716Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Long baseline interferometers
type: Concept
broader: Radio interferometers

Long baseline interferometry
type: Concept
broader: Interferometry

Long period comets
type: Concept
broader: Comets
narrower: Oort cloud
definition: A comet with orbital period of more than 200 years.
modified: 2020-11-03T16:43:14.039Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:43:25.038Z
editorial note: Definition Provenance
  created: 2020-11-03T16:43:25.006Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Long period variable stars
type: Concept
alternative label: Long period variables
alternative label: Long-period variables
broader: Periodic variable stars
broader: Pulsating variable stars
narrower: Mira variable stars
narrower: Semi-regular variable stars
narrower: Slow irregular variable stars
contributor: AAS Frey.Katie Admin
narrower: OGLE small amplitude red giant stars
definition: A type of variable star in which variations in brightness occur over long time-scales of months or years. The term generally refers to Mira variable types.
modified: 2020-12-16T15:40:11.325Z
modified: 2020-11-03T16:44:08.491Z
editorial note: Definition Provenance
  created: 2020-11-03T16:44:08.468Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Longitude of the ascending node
type: Concept
broader: Orbital elements
contributor: AAS Frey.Katie
definition: One of the orbital elements used to specify the orbit of an object in space. It is the angle from the reference direction, called the origin of longitude, to the direction of the ascending node, measured in the reference plane.
modified: 2020-11-10T18:35:12.306Z
editorial note: Definition Provenance
  created: 2020-11-10T18:35:22.364Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-10T18:35:22.392Z

Longitude of the descending node
type: Concept
broader: Orbital elements

Low-density fields
type: Concept
broader: Large-scale structure of the universe

Low-mass x-ray binary stars
type: Concept
alternative label: LMXB
alternative label: LMXBs
alternative label: Low-mass X-ray binaries
broader: X-ray binary stars
narrower: Hz Herculis x-ray binary stars
contributor: AAS Frey.Katie Admin
definition: A member of one of the two main classes of X-ray binary systems where one of the components is a neutron star or black hole and the other component a low-mass star with a spectral type A or later. LMXBs mainly emit soft X-rays. The ratio of their optical to X-ray luminosities is less than 0.1. They belong to old stellar populations with ages 5-15 x 10^9 years and are found in globular clusters and in the bulge of our Milky Way galaxy; some are also found in the disk. Hercules X-1 is an example of LMXBs.
modified: 2020-11-24T17:13:35.977Z
modified: 2020-11-03T16:47:05.813Z
editorial note: Definition Provenance
  created: 2020-11-03T16:47:05.788Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Luminosity classification
type: Concept
alternative label: Luminosity class
broader: Classification systems
narrower: Kappa mechanism
definition: A classification of stellar spectra according to luminosity for a given spectral type. The luminosity class is an indication of a star's surface gravity. It is shown by a Roman numeral as follows: I (supergiants), II (bright giants), III (normal giants), IV (subgiants), and V (dwarf stars, or main-sequence stars). Luminosity classes VI (subdwarfs) and VII (white dwarfs) are rarely used. Subclasses a, b, and c are especially used for supergiants, while the most luminous hypergiants are assigned luminosity class Ia-0.
modified: 2020-11-03T16:49:52.584Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:50:04.359Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:50:04.330Z

Luminosity function
type: Concept
broader: Analytical mathematics
contributor: AAS Frey.Katie
definition: Number distribution of stars or galaxies (galaxy) with respect to their absolute magnitudes. The luminosity function shows the number of stars of a given intrinsic luminosity (or the number of galaxies per integrated magnitude band) in a given volume of space.
modified: 2020-11-10T18:37:23.046Z
modified: 2020-11-10T18:37:33.297Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:37:33.272Z
  creator: AAS Frey.Katie

Luminous arcs
type: Concept
broader: Einstein rings

Luminous blue variable stars
type: Concept
alternative label: Luminous blue variables
broader: Early-type variable stars
broader: Emission line stars
narrower: S Doradus stars
broader: Eruptive variable stars
related: Alpha Cygni variable stars
alternative label: LBV
contributor: AAS Frey.Katie Admin
definition: A high-luminosity variable star, which represents a transition phase in the life of a massive star when it evolves off the main sequence to become a supernova. Only about a dozen confirmed luminous blue variable stars are presently known in our Galaxy.
modified: 2020-12-16T15:42:22.137Z
editorial note: Definition Provenance
  created: 2020-11-03T16:51:17.047Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T16:51:17.071Z

Luminous infrared galaxies
type: Concept
alternative label: LIRG
broader: Infrared galaxies
alternative label: LIRGs
alternative label: IRAS galaxies
contributor: AAS Frey.Katie Admin
definition: A galaxy that emits most of its energy in the infrared and whose infrared luminosity (in the 8-1000 µm range) is more than 10^11 solar luminosities.
modified: 2020-12-16T20:34:05.579Z
modified: 2020-12-04T21:08:17.350Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-12-04T21:08:17.316Z

Lunar atmosphere
type: Concept
broader: Lunar science

Lunar composition
type: Concept
alternative label: Composition of the moon
broader: Lunar interior

Lunar craters
type: Concept
broader: Lunar features
definition: A bowl-like depression on the rigid surface of the Moon, usually caused by the high-speed impact of a colliding object.
related: Craters
contributor: AAS Frey.Katie Admin
broader: Lunar impacts
alternative label: Lunar cratering
modified: 2022-06-15T16:18:36.345Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:42:11.697Z
  creator: AAS Frey.Katie
contributor: AAS Frey.Katie
modified: 2020-11-10T18:42:11.724Z

Astronomical unit
type: Concept
broader: Distance measure
contributor: AAS Frey.Katie Admin
alternative label: AU
alternative label: au
definition: A unit of length equal to 149,597,870,700 m exactly, with symbol 'au' (re-definition at the International Astronomical Union's 28th General Assembly in Beijing, China, August 20-31). The astronomical unit equals 1.5813 x 10^-5 light-years and 4.8481 x 10^-6 parsecs.
modified: 2020-11-24T17:15:52.384Z
modified: 2020-11-05T15:26:30.527Z
editorial note: Definition Provenance
  created: 2020-11-05T15:26:30.497Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Lunar domes
type: Concept
broader: Lunar features
modified: 2020-11-10T18:43:52.541Z
contributor: AAS Frey.Katie
definition: Rounded volcanic structure on the Moon produced by eruption or intrusion of viscous high-silica magma. An uplift that is round or elliptical in map view of the Moon with beds dipping away in all directions from a central point.
editorial note: Definition Provenance
  created: 2020-11-10T18:44:03.862Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
modified: 2020-11-10T18:44:03.888Z

Lunar eclipses
type: Concept
broader: Eclipses
narrower: Saros cycle
definition: The darkening of the Moon which occurs when the Moon enters the umbra of the Earth's shadow. This phenomenon can occur only when the full Moon is near one of the lunar nodes of its orbit around the Earth. There will be a total eclipse if the entire Moon enters the umbra, otherwise the eclipse will be partial when the Moon is somewhat to the north or south of the node and does not cross the shadow entirely. During the eclipse the Moon looks more or less dark, depending especially on the transparency of the Earth's atmosphere. The refraction of Sun's light through the atmosphere sometimes gives a red color to the eclipsed Moon. Colored fringes can be seen around the shadow edge during partial eclipses. Because an eclipse of the Moon is due to the cutting off of the Sun's light, it is visible from the entire hemisphere where the Moon is above the horizon. The maximum duration of a total lunar eclipse, when the Moon passes through the shadow centrally, is 1h 47m.
modified: 2020-11-03T16:52:52.285Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:53:13.353Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:53:13.321Z

Lunar evolution
type: Concept
broader: Lunar science

Lunar features
type: Concept
alternative label: Lunar landmarks
broader: Selenology
narrower: Lunar craters
narrower: Lunar domes
narrower: Lunar highlands
narrower: Lunar maria
narrower: Lunar mountains
narrower: Lunar rays
narrower: Lunar rilles
narrower: Lunar transient phenomena

Lunar geochronology
type: Concept
broader: Lunar surface

Lunar geodesy
type: Concept
alternative label: Lunar geodetics
broader: Selenology

Lunar gravitational field
type: Concept
alternative label: Lunar gravity
broader: Selenology

Lunar highlands
type: Concept
broader: Lunar features
contributor: AAS Frey.Katie
definition: A light color area on the Moon, as contrasted with lunar maria.
modified: 2020-11-10T18:45:02.771Z
modified: 2020-11-10T18:45:12.295Z
editorial note: Definition Provenance
  created: 2020-11-10T18:45:12.265Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Lunar impacts
type: Concept
broader: Lunar surface
editorial note: Suggested to delete. -KF
related: Impact phenomena
contributor: AAS Frey.Katie Admin
narrower: Lunar craters
modified: 2022-06-15T16:18:25.530Z

Lunar interior
type: Concept
broader: Selenology
narrower: Lunar composition
narrower: Lunar seismology

Particle astrophysics
contributor: AAS Frey.Katie Admin
related: Particle physics
type: Concept
broader: High energy astrophysics
narrower: Neutrino oscillations
narrower: Solar neutrinos
narrower: Supernova neutrinos
narrower: Urca process
narrower: Cosmic rays
narrower: Cosmological neutrinos
narrower: Gamma-rays
narrower: Gravitational waves
related: Dark matter
alternative label: Astroparticle physics
modified: 2020-12-03T20:38:35.000Z

Lunar magnetic fields
type: Concept
broader: Selenology

Lunar maria
type: Concept
alternative label: Lunar mare
alternative label: Lunar seas
alternative label: Moon mare
alternative label: Moon maria
alternative label: Moon seas
broader: Lunar features
contributor: AAS Frey.Katie
definition: Areas on the surface of the Moon that appears darker and smoother than their surroundings. Once thought to be seas, lunar maria are now known to be basaltic basins created by volcanic lava floods.
modified: 2020-11-10T18:45:53.655Z
editorial note: Definition Provenance
  created: 2020-11-10T18:46:05.517Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T18:46:05.543Z

Lunar mineralogy
type: Concept
broader: Lunar surface
narrower: Lunar regolith

Lunar mountains
type: Concept
broader: Lunar features

Lunar node regression
type: Concept
broader: Orbital motion
broader: Lunar theory

Lunar occultation
type: Concept
broader: Occultation

Lunar origin
type: Concept
broader: Lunar science

Lunar petrology
type: Concept
broader: Lunar surface

Lunar phase
type: Concept
alternative label: Phase moon
broader: Lunar science
contributor: AAS Frey.Katie
definition: One of the various changes in the apparent shape of the Moon, because as the Moon orbits the Earth different amounts of its illuminated part are facing us. The phases of the Moon include: the new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, waning crescent, and new moon again.
modified: 2020-11-10T18:49:22.832Z
modified: 2020-11-10T18:49:33.366Z
editorial note: Definition Provenance
  created: 2020-11-10T18:49:33.338Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Lunar probes
type: Concept
broader: Space probes
related: Lunar science
definition: A probe for exploring and reporting on conditions on or about the Moon.
modified: 2020-11-03T16:54:16.301Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T16:54:28.910Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:54:28.878Z

Astrophotography
type: Concept
alternative label: Astrophotographers
broader: Astronomical methods
narrower: Remote telescope astrophotography
narrower: Telescope focal plane photography
definition: The photography of stars, other celestial bodies, and stellar fields.
modified: 2020-12-16T16:47:35.447Z
contributor: AAS Frey.Katie Admin
contributor: AAS Frey.Katie
modified: 2020-11-03T18:31:43.103Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:31:43.075Z

Lunar rays
type: Concept
broader: Lunar features
scope note: Refers to lunar feature

Lunar rilles
type: Concept
alternative label: Lunar rills
broader: Lunar features
contributor: AAS Frey.Katie
definition: A long, narrow, straight or sinuous trench or valley with steep walls and roughly parallel sides on the surface of the Moon.
modified: 2020-11-10T18:51:34.879Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:51:47.268Z
modified: 2020-11-10T18:51:47.311Z

Lunar science
type: Concept
alternative label: Lunar physics
broader: Solar system astronomy
narrower: Selenology
narrower: Lunar atmosphere
narrower: Lunar evolution
narrower: Lunar origin
narrower: Lunar phase
narrower: Lunar theory
related: The Moon
related: Lunar probes

Lunar seismology
type: Concept
broader: Lunar interior

Lunar surface
type: Concept
broader: Selenology
narrower: Lunar geochronology
narrower: Lunar impacts
narrower: Lunar mineralogy
narrower: Lunar petrology
related: Natural satellite surfaces
contributor: AAS Frey.Katie Admin
modified: 2020-12-11T18:52:43.962Z

Lunar theory
type: Concept
broader: Celestial mechanics
broader: Lunar science
narrower: Annual equation
narrower: Anomalistic month
narrower: Lunar node regression
scope note: Related to the orbit of the Moon around the Earth.
narrower: Lunation

Lunar transient phenomena
type: Concept
broader: Lunar features
alternative label: Transient lunar phenomenon
contributor: AAS Frey.Katie Admin
alternative label: TLP
definition: A short-lived change in the brightness of patches on the face of the Moon. The TLPs last from a few seconds to a few hours and can grow from less than a few to a hundred kilometers in size. They have been reported by many observers since the invention of the telescope. However, the physical mechanism responsible for creating a TLP is not well understood. Several theories have been proposed, among which lunar outgassing, that is, gas being released from the surface of the Moon.
modified: 2020-11-03T16:55:33.484Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T16:55:47.624Z
modified: 2020-11-03T16:55:47.649Z

Lyman-alpha galaxies
type: Concept
alternative label: LAE
alternative label: Lyman-alpha emitters
broader: Galaxies

Lyman-break galaxies
type: Concept
broader: Galaxies

Astrophysical black holes
type: Concept
broader: Black holes
narrower: Primordial black holes
narrower: Stellar mass black holes
narrower: Supermassive black holes
narrower: Intermediate-mass black holes

Lyman alpha forest
type: Concept
alternative label: Ly-α forest
alternative label: Lyman forest
alternative label: Lyman-alpha forest
alternative label: Lyα forest
broader: Spectroscopy
contributor: AAS Frey.Katie
definition: The appearance of many differentially redshifted Lyman alpha lines in absorption in a quasar's spectrum, caused by intervening hydrogen clouds along our line of sight to the quasar.
modified: 2020-11-10T18:52:29.462Z
modified: 2020-11-10T18:52:38.992Z
editorial note: Definition Provenance
  created: 2020-11-10T18:52:38.958Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Lyman limit systems
type: Concept
broader: Intergalactic clouds

M dwarf stars
contributor: AAS Frey.Katie Admin
type: Concept
alternative label: M dwarfs
broader: Late-type dwarf stars
broader: M stars
alternative label: Red dwarfs
alternative label: M-type main sequence stars
alternative label: M-type dwarf stars
alternative label: M-type dwarfs
broader: Dwarf stars
definition: A star whose spectrum is dominated by the absorption bands of titanium oxide (TiO) and vanadium oxide (VO) and has many neutral metal lines. The effective temperature of M dwarfs ranges from about 3850 to 2600 K. They are low mass stars with masses ranging from 0.6 times that of the Sun at spectral type M0 to less than 0.1 solar masses. M dwarfs are very abundant, they account for about 70-80% of stars in the Galactic disk. The nearest star to the Sun, Proxima Centauri, is an M dwarf.
example: Proxima Centauri
modified: 2022-06-24T15:31:32.428Z
editorial note: Definition Provenance
  created: 2020-11-05T20:23:16.791Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-05T20:23:16.821Z

M stars
type: Concept
alternative label: Class M stars
contributor: AAS Frey.Katie Admin
alternative label: M-type stars
broader: Late-type stars
narrower: Me stars
narrower: M dwarf stars
narrower: M giant stars
narrower: M subdwarf stars
narrower: M subgiant stars
narrower: M supergiant stars
related: Stellar classification
broader: Stellar spectral types
definition: A cool, red star of spectral type M with a surface temperatures of less than 3600 K. The spectra of M stars are dominated by molecular bands, especially those of TiO. Naked-eye examples are Betelgeuse and Antares.
modified: 2020-11-03T16:56:23.335Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T16:56:35.968Z
  creator: AAS Frey.Katie Admin
modified: 2020-11-03T16:56:36.013Z

Mach-Zehnder interferometers
type: Concept
alternative label: Mach Zehnder modulators
alternative label: Mach zehnder interferometers
alternative label: Mach–Zehnder modulators
broader: Optical phase shifting interferometry
broader: Interferometers

Magellanic Stream
type: Concept
broader: High-velocity clouds
broader: Magellanic Clouds
contributor: AAS Frey.Katie
definition: A thin trail of gas stretching from the Magellanic System toward our own Galaxy over about 150° on the sky, corresponding to hundreds of thousands of light-years. This gas consists primarily of neutral hydrogen and is thought to have originated from the Large and Small Magellanic Clouds as a result of tidal interactions with the Milky Way.
modified: 2020-11-10T18:57:44.831Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-10T18:57:54.344Z
modified: 2020-11-10T18:57:54.379Z

Magnetars
type: Concept
broader: Neutron stars
broader: Magnetic stars
narrower: Soft gamma-ray repeaters
definition: A highly magnetized neutron star with fields a thousand times stronger than those of radio pulsars. There are two sub-classes of magnetars, anomalous X-Ray pulsar (AXP)s and soft gamma repeater (SGR)s, that were thought for many years to be separate and unrelated objects. In fact SGRs and AXPs are both neutron stars possessing magnetic fields of unprecedented strength of 10^14 - 10^16 G, and that show both steady X-ray pulsations as well as soft gamma-ray bursts. Their inferred steady X-ray luminosities are about one hundred times higher than their spin-down luminosities, requiring a source of power well beyond the magnetic dipole spin-down that powers rotation-powered pulsar (RPP)s. New high-energy components discovered in the spectra of a number of AXPs and SGRs require non-thermal particle acceleration and look very similar to high-energy spectral components of young rotation-powered pulsars.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T18:27:31.228Z
modified: 2020-11-03T18:27:48.647Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T18:27:48.619Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Magnetic anomalies
type: Concept
broader: Magnetic fields

Magnetic fields
type: Concept
broader: Astrophysical magnetism
narrower: Primordial magnetic fields
narrower: Geomagnetic fields
narrower: Magnetic anomalies
definition: A field of force that is generated by electric currents, or, equivalently, a region in which magnetic forces can be observed.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T18:29:05.952Z
modified: 2020-11-03T18:29:18.006Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-03T18:29:17.972Z

Magnetic stars
type: Concept
alternative label: Cobalt stars
broader: Chemically peculiar stars
narrower: Mercury-manganese stars
narrower: Bp stars
narrower: Am stars
narrower: Magnetars
narrower: Magnetic variable stars
definition: A star whose spectral lines show the Zeeman effect.
modified: 2020-11-03T18:30:21.485Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-11-03T18:30:36.652Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-03T18:30:36.678Z

Magnetic variable stars
type: Concept
broader: Intrinsic variable stars
broader: Magnetic stars
narrower: SX Arietis variable stars
narrower: Rapidly oscillating Ap star
narrower: Am stars

Planetary magnetospheres
type: Concept
narrower: Plasmapause
narrower: Van Allen radiation belts
contributor: AAS Frey.Katie
broader: Planetary science
narrower: Magnetospheric radio emissions
alternative label: Planetary magnetosphere
modified: 2020-10-26T21:34:22.213Z
narrower: Aurorae
narrower: Magnetic poles
narrower: Magnetic storms

Magnetospheric radio emissions
type: Concept
broader: Astronomical techniques
broader: Exoplanet detection methods
broader: Planetary magnetospheres
contributor: AAS Frey.Katie
modified: 2019-12-12T20:58:02.156Z

Magnitude
type: Concept
broader: Astrometry
narrower: Absolute magnitude
narrower: Apparent magnitude
narrower: Integrated magnitude
contributor: AAS Frey.Katie
narrower: Galaxy magnitudes
related: Photometric systems
definition: A measure of brightness in astronomy on a logarithmic scale in which a difference of five magnitudes represents a difference of 100 times in brightness. In this scale the lower a magnitude, the brighter the object. The faintest magnitude reached by unaided eye is 6.
modified: 2020-11-10T19:08:54.441Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie
  created: 2020-11-10T19:10:08.366Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-10T19:10:08.399Z

Radar observations
created: 2022-06-15T19:20:27.409Z
broader: Radar astronomy
type: Concept
creator: AAS Frey.Katie Admin

Astronomy education
creator: AAS Frey.Katie
type: Concept
broader: Interdisciplinary astronomy
created: 2020-10-19T17:17:23.793Z
related: Educational software
contributor: AAS Frey.Katie
scope note: Refers to both methods currently used to teach the science of astronomy and to an area of pedagogical research that seeks to improve those methods.
definition: The act or process of educating in astronomy. The knowledge or abilities gained through being educated in astronomy.
modified: 2020-10-26T18:57:29.314Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-10-26T18:57:44.823Z
modified: 2020-10-26T18:57:44.853Z

Time domain astronomy
type: Concept
broader: Astronomical methods
created: 2019-11-25T18:32:45.840Z
creator: AAS Frey.Katie
related: Variable stars
contributor: AAS Frey.Katie
related: Transient sources
related: Proper motions
scope note: Studying how astronomical objects change over time.
related: Time series analysis
modified: 2019-11-25T18:35:01.099Z

Blazhko effect
broader: RRab variable stars
type: Concept
created: 2019-12-02T16:31:56.556Z
creator: AAS Frey.Katie
broader: RRc variable stars
contributor: AAS Frey.Katie
scope note: This is phenomenon observed in RR Lyr type stars and demonstrates as changes of the light curve on timescales longer than pulsation period. The effect was first found more than 100 years ago and its origin is still not well understood and subject of active research. - https://github.com/astrothesaurus/UAT/issues/286
definition: A long term, generally irregular modulation of light curves of a large subclass of RR Lyrae stars. Most of the modulations occur on the time scale of some 60 periods, although the range extends from some tens to some hundreds of periods. Since its discovery over a hundred years ago, a number of explanations have been proposed for this effect, but its nature is still a matter of investigation. The explanations include: closely spaced pulsation modes, a modal 1:2 resonance, an oblique rotator model, a non-radial modal interaction, convective cycles, and nonlinear resonant mode coupling between the 9th overtone and the fundamental mode.
modified: 2020-11-03T17:48:56.579Z
modified: 2020-11-03T17:49:10.007Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T17:49:09.980Z

Double periodic variable stars
type: Concept
creator: AAS Frey.Katie
created: 2019-12-02T16:54:42.268Z
alternative label: DPV
alternative label: Double periodic variables
broader: Binary stars
broader: Multi-periodic variable stars
scope note: Not to be confused with "Double-mode variable stars."
scope note: Some of the binary stars show additional period that this ~33 times longer than the orbital period and this group is called DPVs. Most of these systems are also showing eclipses, but that's not required. DPVs studied in detail show circumprimary discs. Note that the name seems general, but refers to only a specific group of binary stars. -- https://github.com/astrothesaurus/UAT/issues/286
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:58:47.438Z

Blue large-amplitude pulsators
broader: Pulsating variable stars
type: Concept
creator: AAS Frey.Katie
created: 2019-12-02T16:57:15.144Z
alternative label: BLAP
alternative label: BLAPs
alternative label: Blue large-amplitude pulsating stars
scope note: A class of pulsating variable stars with short periods. These stars are hot (hence "blue" in name) and show relatively large amplitudes. The evolutionary state of these stars is not known. -- https://github.com/astrothesaurus/UAT/issues/286
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:58:18.932Z

Planetary surfaces
broader: Planetary structure
type: Concept
created: 2019-12-02T18:10:41.199Z
creator: AAS Frey.Katie
narrower: Surface variability
narrower: Surface composition
narrower: Surface processes
narrower: Surface ices
alternative label: Planetary surface
related: Exoplanet surfaces
narrower: Regolith
narrower: Impact phenomena
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T17:54:04.203Z

Surface variability
type: Concept
created: 2019-12-02T19:09:09.620Z
creator: AAS Frey.Katie
broader: Planetary surfaces
alternative label: Planetary surface variability
related: Exoplanet surface variability
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T17:44:01.168Z

Surface composition
creator: AAS Frey.Katie
broader: Planetary surfaces
type: Concept
created: 2019-12-02T19:09:20.782Z
alternative label: Planetary surface composition
related: Exoplanet surface composition
modified: 2022-06-21T17:43:49.554Z
contributor: AAS Frey.Katie Admin

Surface processes
creator: AAS Frey.Katie
broader: Planetary surfaces
contributor: AAS Frey.Katie
type: Concept
created: 2019-12-02T19:09:31.078Z
alternative label: Planetary surface processes
modified: 2019-12-19T14:46:46.257Z

Surface ices
created: 2019-12-02T19:09:39.306Z
creator: AAS Frey.Katie
type: Concept
broader: Planetary surfaces
alternative label: Surface ice
contributor: AAS Frey.Katie
alternative label: Planetary surface ices
alternative label: Planetary surface ice
modified: 2019-12-02T19:10:03.385Z

Exoplanet surfaces
type: Concept
broader: Exoplanet structure
creator: AAS Frey.Katie
created: 2019-12-02T19:12:39.542Z
narrower: Exoplanet surface characteristics
contributor: AAS Frey.Katie
related: Planetary surfaces
modified: 2019-12-02T19:13:08.210Z

Atmospheric variability
creator: AAS Frey.Katie
type: Concept
created: 2019-12-02T20:28:36.586Z
broader: Planetary atmospheres
contributor: AAS Frey.Katie
alternative label: Planetary atmospheric variability
related: Exoplanet atmospheric variability
modified: 2019-12-02T20:29:38.484Z

Atmospheric composition
created: 2019-12-02T20:29:11.791Z
type: Concept
broader: Planetary atmospheres
creator: AAS Frey.Katie
related: Exoplanet atmospheric composition
modified: 2019-12-02T20:29:23.449Z
contributor: AAS Frey.Katie

Post-asymptotic giant branch stars
type: Concept
broader: Stellar evolutionary types
creator: AAS Frey.Katie
created: 2019-12-02T20:56:59.995Z
alternative label: Post-AGB stars
related: Post-asymptotic giant branch
definition: A star in a short-lived evolutionary stage evolving from the asymptotic giant branch toward higher effective temperatures. The majority of low and intermediate mass stars (1 to 8 solar masses) are believed to pass through this stage on their way to becoming planetary nebulae.
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T20:30:27.563Z
modified: 2020-11-03T20:30:46.790Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T20:30:46.764Z

Alpha Cygni variable stars
creator: AAS Frey.Katie
broader: Pulsating variable stars
created: 2019-12-02T21:21:47.676Z
type: Concept
alternative label: Alpha Cygni variables
contributor: AAS Frey.Katie
alternative label: A Cyg variables
alternative label: α cyngi variable stars
related: A supergiant stars
related: B supergiant stars
related: Luminous blue variable stars
modified: 2019-12-02T21:24:25.273Z

OGLE small amplitude red giant stars
type: Concept
broader: Long period variable stars
created: 2019-12-03T16:52:41.271Z
creator: AAS Frey.Katie
alternative label: OSARG
contributor: AAS Frey.Katie
alternative label: OSARGs
alternative label: OGLE Small Amplitude Red Giants
alternative label: Optical gravitational lensing experiment small amplitude red giants
alternative label: Optical gravitational lensing experiment small amplitude red giant stars
broader: Multi-periodic variable stars
broader: Red giant stars
modified: 2019-12-03T16:53:47.246Z

Type II Cepheid variable stars
creator: AAS Frey.Katie
created: 2019-12-03T18:40:32.446Z
type: Concept
broader: Cepheid variable stars
narrower: BL Herculis variable stars
contributor: AAS Frey.Katie
narrower: W Virginis variable stars
narrower: RV Tauri variable stars
modified: 2019-12-03T18:41:06.098Z

Galaxy tails
broader: Galaxy structure
type: Concept
creator: AAS Frey.Katie
created: 2019-12-03T18:45:43.961Z
narrower: Tidal tails
modified: 2019-12-03T18:45:56.011Z
contributor: AAS Frey.Katie
narrower: Ram pressure stripped tails

Ram pressure stripped tails
creator: AAS Frey.Katie
type: Concept
broader: Galaxy tails
created: 2019-12-03T18:46:25.610Z

Search for extraterrestrial intelligence
type: Concept
broader: Astrobiology
created: 2019-12-03T18:54:42.656Z
creator: AAS Frey.Katie
narrower: Technosignatures
alternative label: SETI
modified: 2020-11-04T14:39:03.245Z
contributor: AAS Frey.Katie Admin
definition: The scientific attempt to detect intelligent extraterrestrial life by surveying the sky to find the existence of transmissions, especially radio waves or light, from a civilization on a distant planet. The SETI Institute, that carries out the project, is a private non-profit center founded in 1984. There are many methods that SETI scientific teams use to search for extraterrestrial intelligence. Many of these search billions of radio frequencies that reach Earth from all over the Universe, looking for an intelligent radio signal. Other SETI teams search by looking for signals in pulses of light emanating from the stars.
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-11-04T14:39:15.378Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-11-04T14:39:15.403Z

Technosignatures
created: 2019-12-03T18:54:53.328Z
broader: Search for extraterrestrial intelligence
creator: AAS Frey.Katie
type: Concept

Spectral energy distribution
type: Concept
broader: Photometry
creator: AAS Frey.Katie
created: 2019-12-04T19:00:20.200Z
alternative label: SED
contributor: AAS Frey.Katie Admin
definition: A plot showing the energy emitted by a source as a function of the radiation wavelength or frequency. It is used in many branches of astronomy to characterize astronomical sources, in particular mainly in near infrared and middle infrared to study protostars or young stellar objects. The SED of these objects is divided in four classes. Class 0 in which the SED represents a very embedded protostar, where the mass of the central core is small in comparison to the mass of the accreting envelope. The SED is characterized by the blackbody radiation of the envelope and peaks at submillimeter wavelengths. Class I objects possess a SED that peaks in the far infrared and is characterized by a weak contribution of the blackbody of the central protostar (detected in near infrared) and the emission of a thick disk and dense envelope. These objects have less mass in the envelope and more massive central cores with respect to Class 0. Class II objects are the classical T Tauri stars with a SED due to the emission of a thin disk and the central star. They have accumulated most of their final mass and have dispersed almost completely their circumstellar envelope. Finally, Class III objects have pure photospheric spectra. Their SED is peaked in the optical and is well approximated by a blackbody emission with a faint infrared excess due to the presence of a residual optically thin disk that may be the origin of planetesimals. This classification scheme can be made more quantitative by defining a spectral index.
modified: 2020-11-24T19:36:37.304Z
editorial note: Definition Provenance
  created: 2020-11-04T16:25:32.029Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
modified: 2020-11-04T16:25:32.061Z

Astrometric exoplanet detection
broader: Exoplanet detection methods
type: Concept
created: 2019-12-10T19:41:00.906Z
creator: AAS Frey.Katie
related: Astrometry
contributor: AAS Frey.Katie
alternative label: Astrometric planet detection
alternative label: Astrometric planet detection (extrasolar)
modified: 2019-12-10T19:42:13.488Z

Main-belt comets
creator: AAS Frey.Katie
created: 2019-12-11T18:10:51.023Z
broader: Comets
type: Concept

Cold Neptunes
type: Concept
broader: Exoplanets
created: 2019-12-11T18:40:27.355Z
creator: AAS Frey.Katie

Transmission spectroscopy
type: Concept
broader: Spectroscopy
created: 2019-12-11T18:43:40.160Z
creator: AAS Frey.Katie
alternative label: Atmospheric transmission
modified: 2019-12-11T18:43:53.630Z
contributor: AAS Frey.Katie

Radio active galactic nuclei
type: Concept
broader: Active galactic nuclei
created: 2019-12-11T20:02:42.827Z
creator: AAS Frey.Katie
contributor: AAS Frey.Katie
alternative label: Radio AGNs
alternative label: Radio AGN
modified: 2019-12-11T20:19:57.019Z

Stellar occultation
type: Concept
broader: Occultation
creator: AAS Frey.Katie
created: 2019-12-11T20:43:13.625Z
scope note: Occultation of a star by another object.
contributor: AAS Frey.Katie Admin
modified: 2020-11-24T16:43:06.669Z

Binary lens microlensing
broader: Gravitational microlensing
type: Concept
created: 2019-12-13T14:44:59.693Z
creator: AAS Frey.Katie

Triple lens microlensing
broader: Gravitational microlensing
type: Concept
creator: AAS Frey.Katie
created: 2019-12-13T14:45:04.497Z

High-resolution microlensing event imaging
broader: Gravitational microlensing
created: 2019-12-13T14:45:09.691Z
creator: AAS Frey.Katie
type: Concept

Xallarap effect
creator: AAS Frey.Katie
created: 2019-12-13T14:45:14.114Z
type: Concept
contributor: AAS Frey.Katie
broader: Binary source microlensing
modified: 2019-12-13T14:46:34.356Z

Astrometric microlensing effect
created: 2019-12-13T14:45:25.057Z
creator: AAS Frey.Katie
type: Concept
broader: Gravitational microlensing

Binary source microlensing
creator: AAS Frey.Katie
created: 2019-12-13T14:45:31.942Z
type: Concept
broader: Gravitational microlensing
narrower: Xallarap effect
modified: 2019-12-13T14:46:30.237Z
contributor: AAS Frey.Katie

Finite-source photometric effect
created: 2019-12-13T14:45:37.813Z
broader: Gravitational microlensing
type: Concept
creator: AAS Frey.Katie

Lens orbital motion
broader: Gravitational microlensing
created: 2019-12-13T14:45:43.580Z
type: Concept
creator: AAS Frey.Katie

Microlensing parallax
created: 2019-12-13T14:45:49.172Z
broader: Gravitational microlensing
type: Concept
creator: AAS Frey.Katie
related: Parallax
modified: 2019-12-13T14:49:05.303Z
contributor: AAS Frey.Katie
narrower: Satellite microlensing parallax
narrower: Annual microlensing parallax
narrower: Topocentric microlensing parallax

Microlensing optical depth
creator: AAS Frey.Katie
broader: Gravitational microlensing
type: Concept
created: 2019-12-13T14:47:02.861Z

Microlensing event rate
broader: Gravitational microlensing
type: Concept
creator: AAS Frey.Katie
created: 2019-12-13T14:47:34.789Z

Gravitational microlensing exoplanet detection
type: Concept
created: 2019-12-13T14:48:22.496Z
creator: AAS Frey.Katie
broader: Gravitational microlensing
broader: Exoplanet detection methods
contributor: AAS Frey.Katie
related: Free floating planets
alternative label: Gravitational microlensing planet detection
modified: 2019-12-13T15:29:37.050Z

Satellite microlensing parallax
created: 2019-12-13T14:49:14.283Z
broader: Microlensing parallax
type: Concept
creator: AAS Frey.Katie

Annual microlensing parallax
creator: AAS Frey.Katie
created: 2019-12-13T14:49:19.100Z
broader: Microlensing parallax
type: Concept
modified: 2019-12-13T14:50:11.365Z
contributor: AAS Frey.Katie
alternative label: Orbital microlensing parallax

Topocentric microlensing parallax
creator: AAS Frey.Katie
type: Concept
broader: Microlensing parallax
created: 2019-12-13T14:49:24.191Z
contributor: AAS Frey.Katie
alternative label: Geocentric microlensing parallax
alternative label: Terrestrial microlensing parallax
modified: 2019-12-19T14:47:14.371Z

Caustic curve
type: Concept
broader: Gravitational lensing
created: 2019-12-13T14:51:13.931Z
creator: AAS Frey.Katie
narrower: Caustic crossing
contributor: AAS Frey.Katie
definition: The intersection of a caustic surface with a plane passing through the beam of rays.
modified: 2020-11-03T18:58:12.676Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie
  created: 2020-11-03T18:58:24.067Z
modified: 2020-11-03T18:58:24.096Z

Critical curve
type: Concept
created: 2019-12-13T14:51:20.534Z
creator: AAS Frey.Katie
broader: Gravitational lensing

Multiple star evolution
type: Concept
broader: Stellar evolution
creator: AAS Frey.Katie
created: 2019-12-13T20:56:24.720Z
narrower: Common envelope evolution
narrower: Roche lobe overflow

Common envelope evolution
broader: Multiple star evolution
creator: AAS Frey.Katie
created: 2019-12-13T20:56:35.951Z
type: Concept
related: Common envelope binary stars
contributor: AAS Frey.Katie
alternative label: Common envelope episodes
modified: 2019-12-19T14:43:54.362Z

Roche lobe overflow
created: 2019-12-13T20:57:04.439Z
broader: Multiple star evolution
type: Concept
creator: AAS Frey.Katie
related: Roche lobe
contributor: AAS Frey.Katie
modified: 2019-12-13T20:57:19.604Z

Common envelope binary stars
broader: Interacting binary stars
type: Concept
created: 2019-12-13T20:58:03.062Z
creator: AAS Frey.Katie
related: Common envelope evolution
contributor: AAS Frey.Katie
alternative label: Common envelope binaries
modified: 2019-12-13T20:59:37.448Z

Stellar mergers
created: 2019-12-13T20:58:23.101Z
type: Concept
creator: AAS Frey.Katie
broader: Interacting binary stars
contributor: AAS Frey.Katie
modified: 2019-12-13T20:59:02.943Z
alternative label: Merging stars

Neutral coma gases
creator: AAS Frey.Katie
created: 2019-12-13T21:35:33.895Z
type: Concept
broader: Comae

Coma dust
broader: Comae
created: 2019-12-13T21:38:16.546Z
type: Concept
creator: AAS Frey.Katie

Comet nuclei
creator: AAS Frey.Katie
type: Concept
broader: Comets
created: 2019-12-13T21:38:38.278Z
narrower: Comet interiors
contributor: AAS Frey.Katie
narrower: Comet surfaces
narrower: Comet volatiles
definition: The solid, centrally located part of a comet. The nucleus is a mass of dust and frozen gases. When heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma, which is later swept into an elongated tail. Reliable measurements of cometary nuclei indicate sizes from a few km to 10 or 20 km. The nucleus of Comet Hale-Bopp is one of the largest (perhaps 40 km). The composition of the nucleus is determined by measuring the composition of the coma (except for 67P/Churyumov-Gerasimenko). The dominant volatile is water, followed by carbon dioxide, carbon monoxide, formaldehyde, methanol, methane at a few percent level (with respect to water) and many other molecules at a lower level.
modified: 2020-10-26T20:11:25.492Z
editorial note: Definition Provenance
  created: 2020-10-26T20:12:55.598Z
  creator: AAS Frey.Katie
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-10-26T20:12:55.629Z

Comet surfaces
broader: Comet nuclei
created: 2019-12-13T21:39:01.909Z
creator: AAS Frey.Katie
type: Concept

Comet volatiles
type: Concept
broader: Comet nuclei
creator: AAS Frey.Katie
created: 2019-12-13T21:39:17.809Z

Flat-spectrum radio quasars
broader: Blazars
type: Concept
creator: AAS Frey.Katie
created: 2020-09-11T18:11:36.091Z
alternative label: FSRQ
alternative label: OVV quasars
alternative label: Optically violent variable quasars
alternative label: Optically violent variable quasar
alternative label: OVV quasar
alternative label: HPQ
alternative label: Highly polarized quasars
alternative label: Highly polarized quasar
alternative label: CDQ
alternative label: Core-dominated quasars
alternative label: Core-dominated quasar
definition: A member of a small subset of quasars consisting of bright radio galaxies whose flux of visible light output can vary by as much as 50% in a single day.
modified: 2020-11-03T19:57:28.844Z
contributor: AAS Frey.Katie Admin
modified: 2020-11-03T19:58:20.032Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-11-03T19:58:20.007Z

Ultraluminous x-ray sources
creator: AAS Frey.Katie
created: 2020-09-11T18:11:37.156Z
type: Concept
alternative label: ULX
alternative label: Ultraluminous supersoft sources
alternative label: ULS
alternative label: Pulsating ultraluminous X-ray sources
alternative label: PULX
alternative label: Luminous supersoft x-ray source
alternative label: SSXS
alternative label: Supersoft sources
alternative label: SSS
broader: X-ray sources
contributor: AAS Frey.Katie Admin
definition: An X-ray source that is not in the nucleus of a galaxy, and is more luminous than 10^39 ergs s^-1, brighter than the Eddington luminosity of a 10 solar mass black hole. In general, there is about one ULX per galaxy in galaxies which host ULXs. The Milky Way contains no such objects. ULXs are thought to be powered by accretion onto a compact object. Possible explanations include accretion onto neutron stars with strong magnetic fields, onto stellar black holes (of up to 20 solar masses) at or in excess of the classical Eddington limit, or onto intermediate-mass black holes (10^3 - 10^5 solar masses). NGC 1313X-1, NGC 5408X-1, and NGC 6946X-1 are three ULXs with X-ray luminosities up to ~10^40 erg s^-1.
modified: 2020-11-04T21:41:03.492Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-11-04T21:41:16.899Z
modified: 2020-11-04T21:41:16.938Z

Stellar streams
type: Concept
broader: Galaxy structure
created: 2020-10-19T17:57:34.277Z
creator: AAS Frey.Katie
modified: 2020-10-19T18:03:04.320Z
contributor: AAS Frey.Katie

High angular resolution
type: Concept
broader: Astronomical techniques
created: 2020-10-19T19:17:20.612Z
creator: AAS Frey.Katie

AB photometry
type: Concept
broader: Broad band photometry
creator: AAS Frey.Katie
created: 2020-10-21T18:56:26.084Z
contributor: AAS Frey.Katie
alternative label: AB magnitude
alternative label: AB photometric system
alternative label: AB magnitude system
definition: A photometric system defined by reference to monochromatic magnitudes in such a way that AB is equal to the V magnitude for a source with a flat spectral energy distribution. The zero point is defined by the flux of the star Vega at 5546 Å. In this system, an object with constant flux per unit frequency interval has zero color.
modified: 2020-10-26T18:27:50.831Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-10-26T18:28:17.098Z
  creator: AAS Frey.Katie
modified: 2020-10-26T18:28:17.126Z

Vega photometry
broader: Broad band photometry
type: Concept
created: 2020-10-21T18:57:39.238Z
creator: AAS Frey.Katie
alternative label: Vega photometric system
contributor: AAS Frey.Katie
modified: 2020-10-21T18:57:49.592Z

Extreme ultraviolet astronomy
type: Concept
broader: Ultraviolet astronomy
created: 2020-10-21T19:54:36.047Z
creator: AAS Frey.Katie
contributor: AAS Frey.Katie
alternative label: EUV
alternative label: EUV astronomy
modified: 2020-10-21T19:54:53.173Z

Galaxy spectroscopy
type: Concept
broader: Spectroscopy
creator: AAS Frey.Katie
created: 2020-10-21T21:18:06.885Z
contributor: AAS Frey.Katie
related: Galaxies
modified: 2020-10-21T21:20:01.270Z

Extrasolar gaseous planets
type: Concept
broader: Exoplanets
creator: AAS Frey.Katie Admin
created: 2020-11-09T21:31:06.987Z
narrower: Extrasolar gaseous giant planets
contributor: AAS Frey.Katie Admin
alternative label: Extrasolar gas planets
modified: 2020-11-09T21:31:43.871Z

Star-planet interactions
modified: 2020-11-12T21:50:19.030Z
type: Concept
broader: Exoplanet dynamics
created: 2020-11-12T21:46:34.266Z
creator: AAS Frey.Katie Admin
related: Solar-planetary interactions
contributor: AAS Frey.Katie Admin
scope note: Interactions between exoplanets and their stars. The similar concept "Solar-planetary interactions" is specific to interactions between the Sun and Solar system planets.
alternative label: Stellar-planetary interactions
alternative label: Star-exoplanet interactions

Planetary dynamics
broader: Planetary science
type: Concept
creator: AAS Frey.Katie Admin
created: 2020-11-12T19:46:03.598Z
narrower: Volcanism
narrower: Tectonics
narrower: Glaciation

Volcanism
created: 2020-11-12T19:46:38.915Z
type: Concept
broader: Planetary dynamics
creator: AAS Frey.Katie Admin

Tectonics
type: Concept
created: 2020-11-12T19:46:39.018Z
creator: AAS Frey.Katie Admin
broader: Planetary dynamics
contributor: AAS Frey.Katie Admin
related: Volcanoes
narrower: Plate tectonics
modified: 2020-11-12T19:47:37.040Z

Post-starburst galaxies
created: 2020-11-12T20:10:09.570Z
creator: AAS Frey.Katie Admin
broader: Galaxies
type: Concept
alternative label: Post-starburst galaxy
contributor: AAS Frey.Katie Admin
alternative label: Post starburst galaxies
alternative label: Post starburst galaxy
narrower: E+A galaxies
alternative label: PSB
related: Starburst galaxies
modified: 2020-11-12T21:29:51.934Z

Galactic archaeology
type: Concept
broader: Stellar astronomy
created: 2020-11-25T18:48:56.424Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
broader: Milky Way Galaxy physics
modified: 2020-11-25T20:16:45.836Z
definition: Study of galactic evolution through study of stellar populations.

Calibration
type: Concept
broader: Astronomical techniques
creator: AAS Frey.Katie Admin
created: 2020-11-25T20:33:49.668Z
narrower: Flux calibration
modified: 2020-12-03T20:04:16.397Z
contributor: AAS Frey.Katie Admin

Atmospheric clouds
type: Concept
broader: Planetary atmospheres
created: 2020-12-02T21:22:42.892Z
creator: AAS Frey.Katie Admin
narrower: Earth's clouds
modified: 2020-12-02T21:22:54.922Z
contributor: AAS Frey.Katie Admin

Comet Halley
type: Concept
broader: Comets
created: 2020-12-02T21:36:14.047Z
creator: AAS Frey.Katie Admin
definition: The most famous comet orbiting the Sun once about every 75 years. The last time it appeared was in 1986, and it is predicted to return in 2061. Its earliest recorded sighting is traced back to 240 BC in China. In 1705 Edmond Halley used Newton's new theory of gravitation to determine the orbits of comets from their recorded positions in the sky as a function of time. He found that the bright comets of 1531, 1607, and 1682 had almost the same orbits. He concluded that these appearances must belong to a single recurring comet, and predicted its return for 1758. Halley's comet is the first known periodic comet, hence its designation 1P/Halley.
contributor: AAS Frey.Katie Admin
alternative label: 1P/Halley
alternative label: Halley's comet
modified: 2020-12-03T17:39:34.606Z
modified: 2020-12-03T17:39:52.776Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-12-03T17:39:52.738Z
  creator: AAS Frey.Katie Admin

Eros
type: Concept
creator: AAS Frey.Katie Admin
created: 2020-12-02T21:39:02.284Z
contributor: AAS Frey.Katie Admin
alternative label: (433) Eros
alternative label: 433 Eros
alternative label: Asteroid Eros
broader: Amor group
definition: An S-type asteroid about 34.4 × 11.2 × 11.2 km in size, which is the second-largest near-Earth asteroid after 1036 Ganymede. It belongs to the group of Amor asteroids. Eros was discovered on 13 August 1898 by Gustav Witt in Berlin and Auguste Charlois at Nice. It was the first asteroid orbited by an Earth probe (in 2000).
modified: 2020-12-17T16:13:51.922Z
editorial note: Definition Provenance
  created: 2020-12-03T17:40:40.844Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-12-03T17:40:40.880Z

Vesta
created: 2020-12-02T21:44:58.629Z
broader: Main belt asteroids
creator: AAS Frey.Katie Admin
type: Concept
alternative label: (4) Vesta
contributor: AAS Frey.Katie Admin
alternative label: 4 Vesta
modified: 2020-12-02T21:45:17.210Z
alternative label: Asteroid Vesta

Planetary climates
type: Concept
broader: Planetary science
created: 2020-12-02T21:52:04.891Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
related: Planetary atmospheres
modified: 2020-12-02T22:01:42.543Z

Planetary ionospheres
broader: Planetary atmospheres
type: Concept
creator: AAS Frey.Katie Admin
created: 2020-12-02T22:01:27.987Z

Titan
broader: Saturnian satellites
creator: AAS Frey.Katie Admin
created: 2020-12-03T17:29:32.225Z
type: Concept
contributor: AAS Frey.Katie Admin
definition: The largest and the sixth moon of Saturn discovered by Christiaan Huygens in 1655. Called also Saturn VI. Titan has a diameter of 5,150 km, about half the size of Earth and almost as large as Mars. It orbits Saturn at a mean distance of 1,221,830 km every 15.945 days. It is the only moon known to have an atmosphere. Its surface temperature is -179 °C, which makes water as hard as rocks and allows methane to be found in its liquid form. Its surface pressure is slightly higher than Earth's pressure (1.6 bars against 1 bar at sea level). The Huygens probe released from Cassini-Huygens landed on Titan on December 25, 2004. From the data obtained by Cassini-Huygens, we know that Titan is a world with lakes and seas composed of liquid methane and ethane near its poles, with vast, arid regions not made of silicates as on Earth, but of solid water ice coated with hydrocarbons that fall from the atmosphere. Titan's icy dunes are gigantic, reaching, on average, 1 to 2 km wide, hundreds kilometers long and around 100 m high. Titan is the only other place in the solar system known to have an Earth-like cycle of liquids flowing across its surface as the planet cycles through its seasons. Each Titan season lasts about 7.5 Earth years. The Huygens probe made the first direct measurements of Titan's lower atmosphere. Huygens also directly sampled aerosols in the atmosphere and confirmed that carbon and nitrogen are their major constituents. Cassini followed up Huygens' measurements from orbit, detecting other chemicals that include propylene and poisonous hydrogen cyanide, in Titan's atmosphere. Cassini's gravity measurements of Titan revealed that this moon is hiding an internal, liquid water and ammonia ocean beneath its surface. Huygens also measured radio signals during its descent that strongly suggested the presence of an ocean 55 to 80 km below the moon's surface.
modified: 2020-12-03T17:30:37.547Z
modified: 2020-12-03T17:30:58.826Z
editorial note: Definition Provenance
  created: 2020-12-03T17:30:58.792Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin

Triton
created: 2020-12-03T17:31:41.069Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Neptunian satellites
definition: The seventh and the largest of Neptune's satellites. It has a diameter of 2,700 km and orbits its planet at a mean distance of 354,760 km every 5.877 days. Triton was discovered by William Lassell in 1846 scarcely a month after Neptune was discovered. Triton is colder than any other measured object in the solar system with a surface temperature of -235° C. It has an extremely thin atmosphere. Nitrogen ice particles might form thin clouds a few kilometers above the surface. The atmospheric pressure at Triton's surface is about 15 microbars, 0.000015 times the sea-level surface pressure on Earth. Triton is the only large satellite in the solar system to circle a planet in a retrograde motion, that is in a direction opposite to the rotation of the planet.
modified: 2020-12-03T17:31:59.661Z
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  created: 2020-12-03T17:32:11.386Z
  creator: AAS Frey.Katie Admin
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-12-03T17:32:11.410Z

Ganymede
type: Concept
created: 2020-12-03T17:33:19.684Z
creator: AAS Frey.Katie Admin
broader: Galilean satellites
alternative label: Jupiter III
contributor: AAS Frey.Katie Admin
definition: The seventh and largest of Jupiter's known satellites. This Galilean satellite has a diameter of 5270 km, slightly larger than Mercury, a mass about 1.48 × 10^23 kg (about 2 Earth Moons); an orbital period of 7.155 days, and an eccentricity of e = 0.0015. It was discovered by Galileo and Marius in 1610. The mean surface temperature of Ganymede is -160 °C. It is the only moon known to have a magnetosphere.
modified: 2020-12-03T17:36:59.314Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-12-03T17:37:13.759Z
modified: 2020-12-03T17:37:13.790Z

Europa
creator: AAS Frey.Katie Admin
created: 2020-12-03T17:33:38.548Z
type: Concept
broader: Galilean satellites
alternative label: Jupiter II
contributor: AAS Frey.Katie Admin
definition: The sixth of Jupiter's known moons and the fourth largest; it is the second of the Galilean satellites. With a diameter of 3140 km, Europa is slightly smaller than Earth's Moon. Its mass is 4.80 × 10^22 kg, i.e. 1.5 times less massive than Earth Moon. Its distance to Jupiter is 670,900 km, or about 9 Jovian radii. Its orbital period is 3.55 Earth days which equals its rotation period. Europa's density is 3.0 g cm^-3, typical of a mixture of rocks including ice. Its high albedo (0.67) suggests that its surface is mostly water ice. The surface temperature of Europa ranges between about 125 K (-150 °C) at the equator and about 50 K (-220 °C) at the poles. There are few impact craters on Europa, because its surface is too active and therefore young. The most striking features of Europa's surface are structures called lineae and lenticulae. The thickness of the ice crust could range between a few kilometers to a few tens of kilometers. It is now believed that there is an ocean of salty water, up to 100 km deep, flowing under Europa's ice. Europa's ocean is kept liquid due to tidal heating by Jupiter.
modified: 2020-12-03T17:35:27.272Z
modified: 2020-12-03T17:35:44.430Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-12-03T17:35:44.393Z
  creator: AAS Frey.Katie Admin

Io
broader: Galilean satellites
created: 2020-12-03T17:33:55.089Z
type: Concept
creator: AAS Frey.Katie Admin
alternative label: Jupiter I
contributor: AAS Frey.Katie Admin
definition: The fifth of Jupiter's known moons and the third largest. It is the innermost of the Galilean satellites. With a diameter of 3630 km, Io is slightly larger than Earth's Moon. It revolves at a mean distance of 422,000 km from Jupiter. Its mass is 8.93 x 10^22 kg (about 1.2 Earth Moons) and its orbital period 1.8 Earth days. The mean surface temperature of Io is -155 °C. Io's yellow color derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes. The intense tidal force of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons. The resulting friction greatly heats Io's interior, causing molten rock to explode through the surface. Io's volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io's volcanic lava is so hot it glows in the dark.
modified: 2020-12-03T17:38:29.975Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-12-03T17:38:42.648Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-03T17:38:42.687Z

Remote sensing
created: 2020-12-04T16:06:16.832Z
broader: Astronomical techniques
type: Concept
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
definition: Technique that utilizes electromagnetic waves to detect, measure, and obtain information about an object that is not in contact with the sensing apparatus.
scope note: Intended to cover planetary remote sensing, a "catch-all term for any planetary work using remote observations. It would include radar, but also VNIR, TIR, etc. wavelengths."
related: Planetary science
modified: 2020-12-04T16:22:55.352Z
editorial note: Definition Provenance
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  creator: AAS Frey.Katie Admin
  created: 2020-12-04T16:10:54.978Z
modified: 2020-12-04T16:10:55.006Z

Aurorae
broader: Planetary magnetospheres
type: Concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T16:30:01.498Z
contributor: AAS Frey.Katie Admin
definition: A phenomenon consisting of luminous colorful arcs, rays, and streamers that appear in a planet's upper atmosphere during the night with the greatest frequency in the northern and southern polar magnetic zones. This non-thermal radiation is caused by the emission of light from atoms excited by electrons accelerated along the planet's magnetic field lines at the magnetic poles. Fluorescent emission from atomic oxygen at 5557 Å results in a greenish glow, and there is a weaker effect from the red line at 6300 Å. Blue and purple colors are emitted by atomic and molecular nitrogen.
modified: 2020-12-04T16:30:32.975Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-12-04T16:30:57.925Z
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
modified: 2020-12-04T16:30:57.962Z

Lightning
type: Concept
broader: Planetary atmospheres
creator: AAS Frey.Katie Admin
created: 2020-12-04T16:36:13.469Z
modified: 2020-12-04T16:36:56.927Z
definition: A flash of light produced by an electric discharge in response to the buildup of an electric potential between clouds and a planet's surface, or between different portions of the same cloud.
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T16:37:18.774Z
editorial note: Definition Provenance
  comment: Modified from An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
  created: 2020-12-04T16:37:18.737Z
  creator: AAS Frey.Katie Admin

Zodiacal dust bands
type: Concept
broader: Zodiacal cloud
creator: AAS Frey.Katie Admin
created: 2020-12-04T17:57:03.868Z
alternative label: Dust bands
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T20:33:03.480Z
alternative label: IRAS dust bands

Near-sun comets
broader: Comets
type: Concept
created: 2020-12-04T18:39:34.526Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T18:40:12.003Z
definition: Encompasses all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU).
narrower: Sundivers
narrower: Sungrazers
narrower: Sunskirters
modified: 2022-01-04T22:32:33.766Z
editorial note: Definition Provenance
  comment: Jones, GH., et al. 2018, SSRv, 214, 20. 2018SSRv..214...20J
  created: 2022-01-04T22:32:31.236Z
  creator: AAS Frey.Katie Admin

Sundivers
created: 2020-12-04T18:44:42.079Z
type: Concept
broader: Near-sun comets
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
definition: Comets with orbits that intersect the solar photosphere.
alternative label: Sun-plunging
alternative label: Sun-plunger
alternative label: Sun-plunging comet
alternative label: Sun-plunging comets
modified: 2020-12-04T18:57:30.723Z
editorial note: Definition Provenance
  comment: Jones, GH., et al. 2018, SSRv, 214, 20. 2018SSRv..214...20J
  creator: AAS Frey.Katie Admin
  created: 2022-01-04T22:32:19.276Z
modified: 2022-01-04T22:32:40.919Z

Sungrazers
created: 2020-12-04T18:44:50.310Z
broader: Near-sun comets
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
definition: Objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit.
narrower: Kreutz group
modified: 2020-12-04T18:47:40.579Z
modified: 2022-01-04T22:32:05.593Z
editorial note: Definition Provenance
  comment: Jones, GH., et al. 2018, SSRv, 214, 20. 2018SSRv..214...20J
  creator: AAS Frey.Katie Admin
  created: 2022-01-04T22:32:01.759Z

Sunskirters
type: Concept
creator: AAS Frey.Katie Admin
broader: Near-sun comets
created: 2020-12-04T18:44:58.111Z
contributor: AAS Frey.Katie Admin
narrower: Kracht group
narrower: Meyer group
narrower: Marsden group
definition: Objects that pass within 33 solar radii of the Sun's center, equal to half of Mercury's perihelion distance.
modified: 2020-12-17T16:18:51.440Z
modified: 2022-01-04T22:24:06.120Z
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  comment: Jones, GH., et al. 2018, SSRv, 214, 20. 2018SSRv..214...20J
  created: 2022-01-04T22:23:59.373Z

Kracht group
type: Concept
broader: Sunskirters
created: 2020-12-04T18:48:38.671Z
creator: AAS Frey.Katie Admin
modified: 2020-12-04T18:49:45.614Z
contributor: AAS Frey.Katie Admin
alternative label: Kracht sunskirters

Meyer group
creator: AAS Frey.Katie Admin
created: 2020-12-04T18:48:46.492Z
type: Concept
broader: Sunskirters
contributor: AAS Frey.Katie Admin
alternative label: Meyer sunskirters
modified: 2020-12-04T18:49:33.466Z

Marsden group
created: 2020-12-04T18:48:52.594Z
creator: AAS Frey.Katie Admin
broader: Sunskirters
type: Concept
alternative label: Marsden sunskirters
contributor: AAS Frey.Katie Admin
modified: 2020-12-04T18:49:11.741Z

Plutonian satellites
broader: Natural satellites (Solar system)
type: Concept
created: 2020-12-09T15:18:23.572Z
creator: AAS Frey.Katie Admin
example: Charon
contributor: AAS Frey.Katie Admin
example: Nix
example: Styx
example: Kerberos
example: Hydra
alternative label: Moons of Pluto
alternative label: Pluto's moons
alternative label: Charon
modified: 2020-12-09T15:20:31.946Z

Comet origins
type: Concept
broader: Planetary science
created: 2020-12-09T19:29:17.044Z
creator: AAS Frey.Katie Admin
related: Comets
contributor: AAS Frey.Katie Admin
modified: 2020-12-09T19:29:31.052Z

Planetary-disk interactions
creator: AAS Frey.Katie Admin
type: Concept
broader: Planetary science
created: 2020-12-09T19:36:46.118Z

Exoplanet migration
broader: Exoplanet astronomy
type: Concept
creator: AAS Frey.Katie Admin
created: 2020-12-09T19:42:13.352Z
modified: 2020-12-09T19:42:48.835Z
contributor: AAS Frey.Katie Admin
related: Planetary migration

Planetary migration
created: 2020-12-09T19:42:37.867Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Planetary science
modified: 2020-12-09T19:42:48.835Z
related: Exoplanet migration
contributor: AAS Frey.Katie Admin

Asteroid satellites
created: 2020-12-10T20:41:51.494Z
type: Concept
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
alternative label: Asteroid moons
broader: Asteroids
broader: Natural satellites (Solar system)
alternative label: Binary asteroids
alternative label: Binary systems
alternative label: Multiple systems
alternative label: Double asteroids
alternative label: Satellites of asteroids
alternative label: Minor planet moons
alternative label: Binary small Solar System body systems
alternative label: Multiple small Solar System body systems
alternative label: Binary small Solar System bodies
alternative label: Multiple small Solar System bodies
alternative label: Multi-body asteroids
alternative label: Binary SSSB systems
alternative label: Binary SSSBs
alternative label: Multiple SSSB systems
alternative label: Multiple SSSBs
alternative label: Multiple asteroids
alternative label: Asteroid multiples
modified: 2020-12-17T16:07:29.400Z
modified: 2020-12-15T18:16:07.052Z

Asteroid surfaces
creator: AAS Frey.Katie Admin
created: 2020-12-10T21:16:55.634Z
broader: Asteroids
type: Concept

Asteroid dynamics
type: Concept
broader: Planetary science
created: 2020-12-10T21:18:16.982Z
creator: AAS Frey.Katie Admin
narrower: Asteroid rotation
contributor: AAS Frey.Katie Admin
related: Asteroids
modified: 2020-12-10T21:35:46.730Z

Asteroid rotation
broader: Asteroid dynamics
created: 2020-12-10T21:18:28.266Z
type: Concept
creator: AAS Frey.Katie Admin

Natural satellite dynamics
type: Concept
created: 2020-12-10T21:39:48.020Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
broader: Planetary science
related: Natural satellites (Solar system)
modified: 2020-12-11T18:51:21.614Z

Comet dynamics
type: Concept
creator: AAS Frey.Katie Admin
created: 2020-12-10T22:02:46.182Z
broader: Planetary science
contributor: AAS Frey.Katie Admin
related: Comets
modified: 2020-12-10T22:03:15.400Z

Natural satellite surfaces
broader: Planetary science
created: 2020-12-11T18:49:52.783Z
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
related: Natural satellites (Solar system)
related: Lunar surface
modified: 2020-12-11T18:52:43.962Z

Natural satellite atmospheres
creator: AAS Frey.Katie Admin
broader: Planetary science
created: 2020-12-11T18:53:39.323Z
type: Concept
contributor: AAS Frey.Katie Admin
related: Natural satellites (Solar system)
modified: 2020-12-11T18:54:12.514Z

Pulsar wind nebulae
broader: Supernova remnants
type: Concept
creator: AAS Frey.Katie
created: 2022-01-03T15:00:23.709Z
alternative label: Plerion
alternative label: PWN
alternative label: PWNe
broader: Nebulae
related: Pulsars
example: Crab Nebula
definition: A bubble of shocked relativistic particles, produced when a pulsar's relativistic wind interacts with its environment.
contributor: AAS Frey.Katie Admin
modified: 2022-01-04T19:41:35.335Z
editorial note: Definition Provenance
  comment: Gaensler, B. & Slane, P. 2006, ARA&A, 44, 17. 2006ARA&A..44...17G
  created: 2022-01-04T22:08:18.210Z
  creator: AAS Frey.Katie Admin
modified: 2022-01-04T22:08:21.350Z

Astronomy image processing
created: 2022-06-16T14:38:16.028Z
creator: AAS Frey.Katie Admin
broader: Astronomy data analysis
type: Concept

Thermal properties (Ice)
type: Concept
broader: Ice physics
creator: AAS Frey.Katie Admin
created: 2022-06-11T23:01:07.970Z

Atomic data
type: Concept
broader: Atomic physics
creator: AAS Frey.Katie Admin
created: 2022-06-11T21:45:46.289Z

Atomic reactions
type: Concept
creator: AAS Frey.Katie Admin
broader: Atomic physics
created: 2022-06-11T21:46:29.438Z
narrower: Ionization
contributor: AAS Frey.Katie Admin
narrower: Recombination
modified: 2022-06-11T21:47:03.795Z

Charge transfer
broader: Collision physics
type: Concept
created: 2022-06-11T21:48:37.009Z
creator: AAS Frey.Katie Admin

Electron impact excitation
broader: Collision physics
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-11T21:48:57.698Z
contributor: AAS Frey.Katie Admin
modified: 2022-06-11T21:49:32.057Z
alternative label: Electron-impact excitation

Mutual neutralization
type: Concept
broader: Collision physics
creator: AAS Frey.Katie Admin
created: 2022-06-11T21:49:15.424Z

Quadrupole mass spectrometry
modified: 2022-06-27T18:40:51.650Z
created: 2022-06-11T21:52:00.337Z
creator: AAS Frey.Katie Admin
broader: Mass spectrometry
type: Concept
contributor: AAS Frey.Katie Admin

Time-of-flight mass spectrometry
broader: Mass spectrometry
creator: AAS Frey.Katie Admin
created: 2022-06-11T21:52:07.705Z
type: Concept
contributor: AAS Frey.Katie Admin
alternative label: TOFMS
modified: 2022-06-27T18:42:12.273Z

Molecular beams
created: 2022-06-11T21:53:57.193Z
creator: AAS Frey.Katie Admin
broader: Experimental techniques
type: Concept
narrower: Crossed-beams
narrower: Merged-beams
narrower: Supersonic expansion

Ion trapping
created: 2022-06-11T21:54:36.082Z
type: Concept
creator: AAS Frey.Katie Admin
broader: Experimental techniques

Ion-storage rings
created: 2022-06-11T21:54:42.307Z
creator: AAS Frey.Katie Admin
broader: Experimental techniques
type: Concept

Molecular reactions
broader: Molecular physics
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-11T21:56:17.680Z
narrower: Ionization
contributor: AAS Frey.Katie Admin
narrower: Electron recombination reactions
narrower: Ion-neutral reactions
narrower: Isomerization reactions
narrower: Neutral-neutral reactions
narrower: Photodissociation reactions
narrower: Radical-radical recombination
modified: 2022-06-11T22:56:51.934Z

Nuclear decay
type: Concept
broader: Nuclear physics
creator: AAS Frey.Katie Admin
created: 2022-06-11T21:57:38.100Z

Ice physics
type: Concept
creator: AAS Frey.Katie Admin
broader: Solid matter physics
created: 2022-06-11T21:58:41.286Z
narrower: Ice formation
contributor: AAS Frey.Katie Admin
narrower: Ice destruction
narrower: Ice spectroscopy
modified: 2022-06-11T22:46:01.237Z
narrower: Ice composition
narrower: Ice phases
narrower: Ice porosity
narrower: Optical constants (Ice)
narrower: Physical properties (Ice)
narrower: Radiation interactions (Ice)
narrower: Thermal properties (Ice)

Dust physics
created: 2022-06-11T21:58:47.489Z
creator: AAS Frey.Katie Admin
broader: Solid matter physics
type: Concept
narrower: Dust destruction
narrower: Dust formation
narrower: Optical constants (Dust)
narrower: Dust composition

Mineral physics
created: 2022-06-11T21:59:35.186Z
type: Concept
broader: Solid matter physics
creator: AAS Frey.Katie Admin

Reaction models
type: Concept
broader: Theoretical techniques
created: 2022-06-11T22:12:15.889Z
creator: AAS Frey.Katie Admin
narrower: Chemical reaction network models
narrower: Monte Carlo methods
narrower: Reaction rate equations

Quantum-chemical calculations
type: Concept
created: 2022-06-11T22:12:31.484Z
creator: AAS Frey.Katie Admin
broader: Theoretical techniques
narrower: Chemical kinetics
narrower: Potential energy surfaces
narrower: Structure determination
narrower: Chemical thermodynamics

Chemical kinetics
creator: AAS Frey.Katie Admin
broader: Quantum-chemical calculations
type: Concept
created: 2022-06-11T22:12:40.528Z

Potential energy surfaces
broader: Quantum-chemical calculations
type: Concept
created: 2022-06-11T22:12:47.166Z
creator: AAS Frey.Katie Admin

Structure determination
type: Concept
broader: Quantum-chemical calculations
created: 2022-06-11T22:12:53.142Z
creator: AAS Frey.Katie Admin

Chemical thermodynamics
broader: Quantum-chemical calculations
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:13:00.150Z

Chemical reaction network models
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:13:17.876Z
broader: Reaction models
type: Concept

Monte Carlo methods
type: Concept
creator: AAS Frey.Katie Admin
broader: Reaction models
created: 2022-06-11T22:13:23.727Z

Reaction rate equations
broader: Reaction models
type: Concept
created: 2022-06-11T22:13:31.527Z
creator: AAS Frey.Katie Admin

Crossed-beams
created: 2022-06-11T22:17:22.880Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Molecular beams

Merged-beams
broader: Molecular beams
type: Concept
created: 2022-06-11T22:17:28.938Z
creator: AAS Frey.Katie Admin

Supersonic expansion
creator: AAS Frey.Katie Admin
type: Concept
broader: Molecular beams
created: 2022-06-11T22:17:35.286Z

Production techniques
created: 2022-06-11T22:43:49.841Z
creator: AAS Frey.Katie Admin
broader: Experimental techniques
type: Concept
narrower: Electric discharge
narrower: Laser ablation
narrower: Pyrolysis

Electric discharge
creator: AAS Frey.Katie Admin
type: Concept
broader: Production techniques
created: 2022-06-11T22:43:58.105Z

Laser ablation
created: 2022-06-11T22:44:03.983Z
broader: Production techniques
type: Concept
creator: AAS Frey.Katie Admin

Pyrolysis
created: 2022-06-11T22:44:09.943Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Production techniques

Electronic spectroscopy
created: 2022-06-11T22:44:54.905Z
creator: AAS Frey.Katie Admin
broader: Spectroscopy
type: Concept

Rotational spectroscopy
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-11T22:45:40.878Z
broader: Spectroscopy
narrower: Microwave spectroscopy
narrower: Millimeter-wave spectroscopy

Vibrational spectroscopy
broader: Spectroscopy
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:45:47.065Z

Ice spectroscopy
created: 2022-06-11T22:45:52.913Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Spectroscopy
contributor: AAS Frey.Katie Admin
broader: Ice physics
modified: 2022-06-11T22:46:01.237Z

Microwave spectroscopy
broader: Rotational spectroscopy
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:46:15.579Z
narrower: Cavity-enhanced Fourier-transform
contributor: AAS Frey.Katie Admin
narrower: Chirped-pulse Fourier-transform
narrower: Direct absorption
modified: 2022-06-11T22:49:19.993Z

Millimeter-wave spectroscopy
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-11T22:46:21.493Z
broader: Rotational spectroscopy
narrower: Cavity-enhanced Fourier-transform
narrower: Chirped-pulse Fourier-transform
narrower: Direct absorption

Cavity-enhanced Fourier-transform
created: 2022-06-11T22:47:50.902Z
creator: AAS Frey.Katie Admin
broader: Millimeter-wave spectroscopy
type: Concept
modified: 2022-06-11T22:48:42.787Z
contributor: AAS Frey.Katie Admin
broader: Microwave spectroscopy

Chirped-pulse Fourier-transform
broader: Millimeter-wave spectroscopy
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-11T22:47:57.661Z
contributor: AAS Frey.Katie Admin
alternative label: CP-FTMW
broader: Microwave spectroscopy
modified: 2022-06-11T22:49:07.095Z

Direct absorption
broader: Millimeter-wave spectroscopy
type: Concept
created: 2022-06-11T22:48:03.431Z
creator: AAS Frey.Katie Admin
modified: 2022-06-11T22:49:19.993Z
contributor: AAS Frey.Katie Admin
broader: Microwave spectroscopy

Complex organic molecules
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:51:15.924Z
type: Concept
broader: Molecular physics
contributor: AAS Frey.Katie Admin
modified: 2022-06-11T22:51:25.005Z
alternative label: COMs

Fullerenes
creator: AAS Frey.Katie Admin
broader: Molecular physics
type: Concept
created: 2022-06-11T22:53:35.149Z

Metal-containing molecules
created: 2022-06-11T22:53:46.264Z
broader: Molecular physics
creator: AAS Frey.Katie Admin
type: Concept

Molecular data
type: Concept
broader: Molecular physics
created: 2022-06-11T22:54:38.246Z
creator: AAS Frey.Katie Admin
narrower: Molecular spectroscopic constants
narrower: Molecular structural parameters

Molecular spectroscopic constants
created: 2022-06-11T22:54:59.606Z
broader: Molecular data
creator: AAS Frey.Katie Admin
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2022-06-11T22:55:29.485Z

Molecular structural parameters
type: Concept
created: 2022-06-11T22:55:13.005Z
creator: AAS Frey.Katie Admin
broader: Molecular data

Electron recombination reactions
broader: Molecular reactions
type: Concept
created: 2022-06-11T22:56:05.408Z
creator: AAS Frey.Katie Admin

Ion-neutral reactions
broader: Molecular reactions
created: 2022-06-11T22:56:17.323Z
type: Concept
creator: AAS Frey.Katie Admin

Isomerization reactions
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:56:23.091Z
type: Concept
broader: Molecular reactions

Neutral-neutral reactions
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-11T22:56:28.691Z
broader: Molecular reactions

Photodissociation reactions
created: 2022-06-11T22:56:34.623Z
type: Concept
broader: Molecular reactions
creator: AAS Frey.Katie Admin
related: Photodissociation regions
modified: 2022-06-11T22:57:38.308Z
contributor: AAS Frey.Katie Admin

Small molecules
created: 2022-06-11T22:59:01.975Z
type: Concept
creator: AAS Frey.Katie Admin
broader: Molecular physics

Dust destruction
created: 2022-06-11T22:59:47.325Z
creator: AAS Frey.Katie Admin
broader: Dust physics
type: Concept

Dust formation
type: Concept
creator: AAS Frey.Katie Admin
broader: Dust physics
created: 2022-06-11T22:59:53.293Z

Optical constants (Dust)
created: 2022-06-11T22:59:59.642Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Dust physics

Dust composition
type: Concept
broader: Dust physics
creator: AAS Frey.Katie Admin
created: 2022-06-11T23:00:05.686Z

Ice composition
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-11T23:00:29.772Z
broader: Ice physics

Ice phases
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-11T23:00:35.782Z
broader: Ice physics

Ice porosity
created: 2022-06-11T23:00:41.611Z
broader: Ice physics
creator: AAS Frey.Katie Admin
type: Concept

Optical constants (Ice)
creator: AAS Frey.Katie Admin
type: Concept
broader: Ice physics
created: 2022-06-11T23:00:48.190Z

Physical properties (Ice)
created: 2022-06-11T23:00:54.272Z
type: Concept
broader: Ice physics
creator: AAS Frey.Katie Admin

Radiation interactions (Ice)
created: 2022-06-11T23:01:01.100Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Ice physics

Callisto
creator: AAS Frey.Katie Admin
type: Concept
broader: Galilean satellites
created: 2022-06-15T15:31:10.537Z

Enceladus
type: Concept
created: 2022-06-15T15:32:21.698Z
creator: AAS Frey.Katie Admin
broader: Saturnian satellites

Adaptive optics
type: Concept
broader: Astronomical optics
creator: AAS Frey.Katie Admin
created: 2022-06-15T16:02:03.138Z

Craters
broader: Impact phenomena
type: Concept
created: 2022-06-15T16:17:24.497Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
alternative label: Cratering
related: Lunar craters
modified: 2022-06-15T16:17:40.622Z

Gamma-ray spectroscopy
broader: Spectroscopy
type: Concept
created: 2022-06-15T16:24:34.391Z
creator: AAS Frey.Katie Admin
alternative label: Gamma ray spectroscopy
modified: 2022-06-16T20:18:17.811Z
contributor: AAS Frey.Katie Admin

Ultraviolet spectroscopy
type: Concept
creator: AAS Frey.Katie Admin
broader: Spectroscopy
created: 2022-06-15T16:24:40.909Z
contributor: AAS Frey.Katie Admin
alternative label: UV spectroscopy
modified: 2022-06-15T19:29:08.211Z

Infrared spectroscopy
created: 2022-06-15T16:24:48.929Z
creator: AAS Frey.Katie Admin
broader: Spectroscopy
type: Concept

Collisional processes
type: Concept
broader: Planetary science
created: 2022-06-15T19:13:06.506Z
creator: AAS Frey.Katie Admin
modified: 2022-06-15T19:13:44.093Z
contributor: AAS Frey.Katie Admin
scope note: Collisional processes within planetary systems.

Planetary thermal histories
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-15T19:23:10.628Z
contributor: AAS Frey.Katie Admin
broader: Planetary science
modified: 2022-06-16T14:22:14.732Z

Planetary geology
type: Concept
broader: Planetary structure
creator: AAS Frey.Katie Admin
created: 2022-06-15T19:21:43.758Z
narrower: Geological processes
narrower: Planetary mineralogy

Geological processes
created: 2022-06-15T19:22:17.181Z
creator: AAS Frey.Katie Admin
broader: Planetary geology
type: Concept

James Webb Space Telescope
creator: AAS Frey.Katie Admin
created: 2022-06-15T19:26:45.836Z
type: Concept
broader: Space observatories
broader: Infrared observatories
alternative label: JWST
contributor: AAS Frey.Katie
modified: 2024-06-20T12:33:00.473Z

Planetary system evolution
created: 2022-06-15T19:31:19.167Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Planetary science
narrower: Solar system evolution

Solar system evolution
type: Concept
created: 2022-06-15T19:31:29.971Z
creator: AAS Frey.Katie Admin
broader: Planetary system evolution
related: Solar system
contributor: AAS Frey.Katie Admin
modified: 2022-06-15T19:31:40.808Z

Regolith
type: Concept
broader: Planetary surfaces
created: 2022-06-15T19:34:18.118Z
creator: AAS Frey.Katie Admin
modified: 2022-06-21T18:20:02.688Z
related: Lunar regolith
contributor: AAS Frey.Katie Admin

Ring resonance
broader: Planetary rings
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-15T19:52:32.860Z

Spin-orbit resonances
broader: Orbits
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-15T19:54:10.781Z

Natural satellite evolution
broader: Planetary science
type: Concept
contributor: AAS Frey.Katie Admin
created: 2022-06-15T19:55:53.000Z
creator: AAS Frey.Katie Admin
modified: 2022-06-27T18:47:35.058Z

Solid body tides
broader: Tides
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-15T19:57:25.781Z

Impact gardening
broader: Impact phenomena
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-16T14:15:31.038Z

Atmospheric dynamics
type: Concept
broader: Planetary atmospheres
created: 2022-06-16T14:18:19.994Z
creator: AAS Frey.Katie Admin
alternative label: Atmosphere dynamics
contributor: AAS Frey.Katie Admin
related: Exoplanet atmospheric dynamics
modified: 2022-06-21T17:40:56.319Z

Atmospheric evolution
created: 2022-06-16T14:18:32.900Z
type: Concept
broader: Planetary atmospheres
creator: AAS Frey.Katie Admin
related: Exoplanet atmospheric evolution
contributor: AAS Frey.Katie Admin
alternative label: Atmosphere evolution
modified: 2022-06-21T17:40:32.972Z

Glaciation
type: Concept
broader: Planetary dynamics
created: 2022-06-16T14:19:37.207Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2022-06-16T14:20:00.237Z
related: Glaciers

Glaciers
broader: Planetary structure
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-16T14:19:53.689Z
contributor: AAS Frey.Katie Admin
modified: 2022-06-16T14:20:00.236Z
related: Glaciation

Planetary mineralogy
broader: Planetary geology
creator: AAS Frey.Katie Admin
created: 2022-06-16T14:20:55.668Z
type: Concept

Astronomy data sonification
broader: Astronomy data analysis
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-16T14:38:08.137Z
contributor: AAS Frey.Katie Admin
modified: 2022-06-30T20:55:34.676Z

Exoplanet atmospheric dynamics
type: Concept
broader: Exoplanet atmospheres
created: 2022-06-21T17:38:06.497Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
alternative label: Exoplanet atmosphere dynamics
related: Atmospheric dynamics
modified: 2022-06-21T17:40:56.320Z

Exoplanet atmospheric evolution
broader: Exoplanet atmospheres
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T17:38:52.004Z
contributor: AAS Frey.Katie Admin
alternative label: Exoplanet atmosphere evolution
related: Atmospheric evolution
modified: 2022-06-21T17:40:23.177Z

Atmospheric structure
broader: Planetary atmospheres
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T17:41:57.414Z
alternative label: Atmosphere structure
contributor: AAS Frey.Katie Admin
related: Exoplanet atmospheric structure
modified: 2022-06-21T17:43:02.819Z

Exoplanet atmospheric structure
creator: AAS Frey.Katie Admin
type: Concept
broader: Exoplanet atmospheres
created: 2022-06-21T17:42:29.780Z
contributor: AAS Frey.Katie Admin
alternative label: Exoplanet atmosphere structure
related: Atmospheric structure
modified: 2022-06-21T17:43:02.819Z

Earth's seasons
type: Concept
broader: Earth atmosphere
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:15:55.340Z
related: Seasonal phenomena
modified: 2022-06-21T18:16:05.244Z
contributor: AAS Frey.Katie Admin

Comet dust tails
type: Concept
broader: Comet tails
created: 2022-06-21T18:16:30.610Z
creator: AAS Frey.Katie Admin

Comet ion tails
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T18:16:43.147Z
broader: Comet tails

Greenhouse effect
creator: AAS Frey.Katie Admin
broader: Earth atmosphere
created: 2022-06-21T18:18:52.467Z
type: Concept
narrower: Greenhouse gases
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:19:02.252Z

Lunar regolith
broader: Lunar mineralogy
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:19:56.300Z
related: Regolith
modified: 2022-06-21T18:20:02.688Z
contributor: AAS Frey.Katie Admin

Lunation
broader: Lunar theory
type: Concept
created: 2022-06-21T18:21:01.179Z
creator: AAS Frey.Katie Admin

Pallas
creator: AAS Frey.Katie Admin
type: Concept
broader: Main belt asteroids
created: 2022-06-21T18:30:49.562Z

Light pollution
broader: Night sky brightness
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:32:01.067Z

Magnetic poles
type: Concept
broader: Planetary magnetospheres
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:32:25.565Z

Magnetic storms
broader: Planetary magnetospheres
created: 2022-06-21T18:32:38.676Z
type: Concept
creator: AAS Frey.Katie Admin
modified: 2022-06-21T18:32:45.698Z
contributor: AAS Frey.Katie Admin

Albedo
broader: Planetary science
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T18:33:24.954Z

Kepler's laws
type: Concept
broader: Celestial mechanics
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:40:41.573Z

Nuclear fission
broader: Nuclear astrophysics
type: Concept
created: 2022-06-21T18:40:59.247Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:41:27.582Z

Nuclear fusion
broader: Nuclear astrophysics
created: 2022-06-21T18:41:12.217Z
type: Concept
creator: AAS Frey.Katie Admin

Analemma
type: Concept
broader: Orbital motion
created: 2022-06-21T18:41:52.573Z
creator: AAS Frey.Katie Admin

Prograde orbit
broader: Orbital motion
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:43:12.764Z

Retrograde orbit
type: Concept
created: 2022-06-21T18:43:21.783Z
broader: Orbital motion
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:43:30.252Z

Stellar aberration
broader: Astrometry
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:52:06.085Z
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:53:09.202Z

Binoculars
type: Concept
broader: Astronomical instrumentation
created: 2022-06-21T18:52:21.833Z
creator: AAS Frey.Katie Admin

Optical aberration
created: 2022-06-21T18:53:55.511Z
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomical optics
narrower: Chromatic aberration
narrower: Spherical aberration

Optical filters
created: 2022-06-21T18:54:04.904Z
creator: AAS Frey.Katie Admin
broader: Astronomical optics
type: Concept

Asterisms
type: Concept
broader: Celestial sphere
creator: AAS Frey.Katie Admin
created: 2022-06-21T18:55:04.222Z

Gnomons
type: Concept
created: 2022-06-21T18:55:52.334Z
creator: AAS Frey.Katie Admin
broader: Sundials
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T18:56:51.249Z

Planispheres
broader: Early astronomical instruments
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T18:56:00.033Z

Sundials
creator: AAS Frey.Katie Admin
broader: Early astronomical instruments
created: 2022-06-21T18:56:17.113Z
type: Concept
contributor: AAS Frey.Katie Admin
narrower: Gnomons
modified: 2022-06-30T20:55:22.584Z

Ecliptic
creator: AAS Frey.Katie Admin
type: Concept
broader: Ecliptic coordinate system
created: 2022-06-21T19:59:59.372Z

Zodiac
type: Concept
created: 2022-06-21T20:00:09.823Z
creator: AAS Frey.Katie Admin
broader: Ecliptic coordinate system

Circumpolar
broader: Equatorial coordinate system
type: Concept
created: 2022-06-21T20:01:35.531Z
creator: AAS Frey.Katie Admin

Horizon
broader: Horizontal coordinate system
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T20:02:36.123Z

Cardinal directions
broader: Horizontal coordinate system
type: Concept
created: 2022-06-21T20:02:49.034Z
creator: AAS Frey.Katie Admin

Zenith distance
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T20:03:19.312Z
broader: Horizontal coordinate system

Chromatic aberration
broader: Optical aberration
created: 2022-06-21T20:03:53.603Z
creator: AAS Frey.Katie Admin
type: Concept

Spherical aberration
broader: Optical aberration
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-21T20:04:01.355Z

Eye pieces
created: 2022-06-21T20:05:35.302Z
type: Concept
broader: Optical telescopes
creator: AAS Frey.Katie Admin

Primary mirror
broader: Reflecting telescopes
type: Concept
created: 2022-06-21T20:05:53.838Z
creator: AAS Frey.Katie Admin

Secondary mirror
creator: AAS Frey.Katie Admin
broader: Reflecting telescopes
created: 2022-06-21T20:05:59.989Z
type: Concept

Lenses
broader: Refracting telescopes
type: Concept
created: 2022-06-21T20:06:17.940Z
creator: AAS Frey.Katie Admin

Space stations
type: Concept
broader: Space vehicles
created: 2022-06-21T20:08:10.322Z
creator: AAS Frey.Katie Admin
narrower: International Space Station

International Space Station
type: Concept
creator: AAS Frey.Katie Admin
broader: Space stations
created: 2022-06-21T20:09:42.260Z

Telescope properties
type: Concept
broader: Telescopes
created: 2022-06-21T20:10:29.674Z
creator: AAS Frey.Katie Admin
narrower: Aperture
narrower: Focal length
narrower: Focal ratio
narrower: Prime focus

Aperture
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T20:10:42.651Z
broader: Telescope properties

Focal length
broader: Telescope properties
created: 2022-06-21T20:10:49.117Z
creator: AAS Frey.Katie Admin
type: Concept

Focal ratio
broader: Telescope properties
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T20:10:55.540Z

Prime focus
created: 2022-06-21T20:11:02.079Z
type: Concept
broader: Telescope properties
creator: AAS Frey.Katie Admin

Rockets
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-21T20:11:27.162Z
broader: Space vehicles

Keplerian telescopes
broader: Refracting telescopes
created: 2022-06-21T20:49:41.715Z
creator: AAS Frey.Katie Admin
type: Concept

Galilean telescopes
created: 2022-06-21T20:49:47.943Z
broader: Refracting telescopes
creator: AAS Frey.Katie Admin
type: Concept

Star lore
created: 2022-06-21T20:50:30.355Z
type: Concept
broader: Celestial sphere
creator: AAS Frey.Katie Admin
alternative label: Starlore
contributor: AAS Frey.Katie Admin
modified: 2022-06-21T20:52:11.981Z

Magnetogram
creator: AAS Frey.Katie Admin
type: Concept
broader: Astronomical techniques
created: 2022-06-21T20:55:00.871Z

Gaia
type: Concept
created: 2022-06-21T21:11:35.375Z
creator: AAS Frey.Katie Admin
broader: Space observatories

Geocentric model
type: Concept
broader: Cosmological models
creator: AAS Frey.Katie Admin
created: 2022-06-22T19:42:55.254Z

Heliocentric model
creator: AAS Frey.Katie Admin
type: Concept
broader: Cosmological models
created: 2022-06-22T19:43:02.617Z

Cosmological principle
broader: Cosmology
type: Concept
created: 2022-06-22T19:43:54.177Z
creator: AAS Frey.Katie Admin

Galaxy bars
broader: Barred spiral galaxies
type: Concept
created: 2022-06-22T19:44:30.507Z
creator: AAS Frey.Katie Admin
modified: 2022-06-22T19:47:12.897Z
contributor: AAS Frey.Katie Admin
related: Galactic bar

Galactic bar
broader: Milky Way Galaxy physics
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-22T19:47:04.619Z
modified: 2022-06-22T19:47:12.897Z
contributor: AAS Frey.Katie Admin
related: Galaxy bars

Cultural astronomy
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-22T19:49:10.393Z
broader: Interdisciplinary astronomy
contributor: AAS Frey.Katie Admin
narrower: Archaeoastronomy
narrower: Ethnoastronomy
broader: Astronomical research
modified: 2024-06-20T13:24:39.951Z

Indigenous astronomy
creator: AAS Frey.Katie Admin
type: Concept
created: 2022-06-22T19:49:16.856Z
broader: Ethnoastronomy
contributor: AAS Frey.Katie Admin
modified: 2022-06-24T17:25:08.586Z

Exocomets
broader: Exoplanet astronomy
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-24T15:11:50.039Z
alternative label: Comets (Extrasolar)
contributor: AAS Frey.Katie Admin
related: Comets
scope note: Not to be confused with Interstellar objects.
related: Interstellar objects
modified: 2022-06-24T15:14:32.957Z

High contrast techniques
type: Concept
broader: Direct imaging
created: 2022-06-30T15:02:27.681Z
creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
narrower: Coronagraphic imaging
alternative label: High contrast imaging
modified: 2022-06-30T15:05:56.143Z
narrower: High contrast spectroscopy

High contrast spectroscopy
created: 2022-06-30T15:09:16.232Z
broader: High contrast techniques
type: Concept
creator: AAS Frey.Katie Admin

Experimental data
broader: Laboratory astrophysics
type: Concept
creator: AAS Frey.Katie Admin
created: 2022-06-30T15:12:19.844Z

Theoretical data
broader: Laboratory astrophysics
created: 2022-06-30T15:12:26.115Z
creator: AAS Frey.Katie Admin
type: Concept

Stephan's quintet
deprecated: true
type: Concept
change note: Use instead
  comment: Galaxy groups
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T16:35:30.217Z
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:35:30.249Z

Natural decay
type: Concept
deprecated: true

Molecule destruction
deprecated: true
type: Concept

Molecule formation
type: Concept
deprecated: true

Experimental models
deprecated: true
type: Concept

Darkrooms
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T16:47:28.645Z
  comment: Astrophotography
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T16:47:28.674Z
contributor: AAS Frey.Katie Admin

Helium abundance
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T19:26:35.486Z
  comment: Chemical abundances
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T19:26:35.521Z
contributor: AAS Frey.Katie Admin

Ixion
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:29:42.365Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Plutinos
  created: 2020-12-16T20:29:42.328Z

Huya
type: Concept
deprecated: true
modified: 2020-12-16T15:32:34.010Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T15:32:33.979Z
  comment: Classical Kuiper belt objects
  creator: AAS Frey.Katie Admin

Far-infrared astronomy
deprecated: true
type: Concept
modified: 2020-12-16T15:37:57.312Z
change note: Use instead
  comment: Far infrared astronomy
  created: 2020-12-16T15:37:57.284Z
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin

Long period variable stars
deprecated: true
type: Concept
modified: 2020-12-16T15:39:58.004Z
change note: Use instead
  comment: Long period variable stars
  created: 2020-12-16T15:39:57.971Z
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin

Luminous blue variables
deprecated: true
type: Concept
change note: Use instead
  created: 2020-12-16T15:41:38.625Z
  creator: AAS Frey.Katie Admin
  comment: Luminous blue variable stars
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:41:38.652Z

Mira variable stars
deprecated: true
type: Concept
modified: 2020-12-16T15:43:18.283Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Mira variable stars
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T15:43:18.250Z

Neutrino oscillation
type: Concept
deprecated: true
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T15:44:32.641Z
  comment: Neutrino oscillations
modified: 2020-12-16T15:44:32.674Z
contributor: AAS Frey.Katie Admin

FU Orionis stars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: FU Orionis stars
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T15:45:56.946Z
modified: 2020-12-16T15:45:56.976Z

R Coronae Borealis stars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: R Coronae Borealis variable stars
  created: 2020-12-16T15:47:28.203Z
modified: 2020-12-16T15:47:28.238Z

I galaxies
deprecated: true
type: Concept
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Irregular galaxies
  created: 2020-12-16T15:48:40.543Z
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:48:40.573Z

RRb stars
deprecated: true
type: Concept
change note: Use instead
  created: 2020-12-16T15:49:48.846Z
  creator: AAS Frey.Katie Admin
  comment: RRab variable stars
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:49:48.880Z

RRA stars
deprecated: true
type: Concept
change note: Use instead
  created: 2020-12-16T15:50:08.414Z
  creator: AAS Frey.Katie Admin
  comment: RRab variable stars
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:50:08.448Z

Gamma-ray telescopes
deprecated: true
type: Concept
modified: 2020-12-16T15:51:35.243Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Gamma-ray telescopes
  created: 2020-12-16T15:51:35.216Z

Continuum radio emission
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T15:52:52.853Z
change note: Use instead
  created: 2020-12-16T15:52:52.824Z
  creator: AAS Frey.Katie Admin
  comment: Radio continuum emission

Bailey type stars
deprecated: true
type: Concept
modified: 2020-12-16T15:54:11.926Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: RR Lyrae variable stars
  created: 2020-12-16T15:54:11.901Z
contributor: AAS Frey.Katie Admin

Henry Draper Catalogue
deprecated: true
type: Concept
change note: Use instead
  comment: Henry Draper catalog
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T15:55:41.071Z
modified: 2020-12-16T15:55:41.102Z
contributor: AAS Frey.Katie Admin

Galaxy components
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Galaxy structure
  created: 2020-12-16T15:56:56.960Z
modified: 2020-12-16T15:56:56.989Z

Elemental abundance
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T15:58:12.112Z
  creator: AAS Frey.Katie Admin
  comment: Chemical abundances
modified: 2020-12-16T15:58:12.142Z

Solar composition
deprecated: true
type: Concept
change note: Use instead
  comment: Solar abundances
  created: 2020-12-16T15:59:22.539Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T15:59:22.573Z
contributor: AAS Frey.Katie Admin

Solar magnetism
type: Concept
deprecated: true
change note: Use instead
  comment: Solar magnetic fields
  created: 2020-12-16T16:00:34.882Z
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:00:34.908Z

Stellar chemical composition
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:29:25.699Z
change note: Use instead
  created: 2020-12-16T16:29:25.664Z
  comment: Stellar abundances
  creator: AAS Frey.Katie Admin

Stellar composition
deprecated: true
type: Concept
change note: Use instead
  comment: Stellar abundances
  created: 2020-12-16T16:29:10.332Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T16:29:10.363Z
contributor: AAS Frey.Katie Admin

Stellar elemental abundances
deprecated: true
type: Concept
change note: Use instead
  comment: Stellar abundances
  created: 2020-12-16T16:28:48.932Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T16:28:48.968Z
contributor: AAS Frey.Katie Admin

Seyfert's sextet
deprecated: true
type: Concept
modified: 2020-12-16T16:32:10.178Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Galaxy groups
  created: 2020-12-16T16:32:10.153Z
  creator: AAS Frey.Katie Admin

Fork mounts
deprecated: true
type: Concept
change note: Use instead
  created: 2020-12-16T16:49:56.268Z
  creator: AAS Frey.Katie Admin
  comment: Equatorial mounts
modified: 2020-12-16T16:49:56.297Z
contributor: AAS Frey.Katie Admin

Yoke mounts
deprecated: true
type: Concept
modified: 2020-12-16T16:51:10.475Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Equatorial mounts
  created: 2020-12-16T16:51:10.446Z
contributor: AAS Frey.Katie Admin

English mounts
type: Concept
deprecated: true
change note: Use instead
  comment: Equatorial mounts
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T16:49:33.645Z
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T16:49:33.684Z

German equatorial mounts
deprecated: true
type: Concept
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T16:50:20.604Z
  comment: Equatorial mounts
modified: 2020-12-16T16:50:20.641Z
contributor: AAS Frey.Katie Admin

Horseshoe mounts
type: Concept
deprecated: true
modified: 2020-12-16T16:50:47.088Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T16:50:47.056Z
  comment: Equatorial mounts

Two-spectrum binary stars
type: Concept
deprecated: true
modified: 2020-12-16T16:53:11.830Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T16:53:11.802Z
  comment: Spectroscopic binary stars
contributor: AAS Frey.Katie Admin

Compact binary components
deprecated: true
type: Concept
modified: 2020-12-16T18:55:19.859Z
change note: Use instead
  comment: Compact binary stars
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T18:55:19.825Z
contributor: AAS Frey.Katie Admin

Compact binary systems
type: Concept
deprecated: true
modified: 2020-12-16T18:54:57.714Z
change note: Use instead
  comment: Compact binary stars
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T18:54:57.669Z
contributor: AAS Frey.Katie Admin

Equinox correction
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T18:57:45.507Z
change note: Use instead
  comment: Equatorial coordinate system
  created: 2020-12-16T18:57:45.472Z
  creator: AAS Frey.Katie Admin

Eruptive binary stars
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T18:59:26.921Z
  comment: Close binary stars
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T18:59:26.953Z

Accreting binary stars
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T18:59:55.142Z
  comment: Close binary stars
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T18:59:55.170Z

Disk population
type: Concept
deprecated: true
modified: 2020-12-16T19:01:20.987Z
change note: Use instead
  comment: Population II stars
  created: 2020-12-16T19:01:20.951Z
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin

Disk stars
type: Concept
deprecated: true
modified: 2020-12-16T19:02:11.596Z
change note: Use instead
  created: 2020-12-16T19:02:11.572Z
  comment: Population II stars
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin

Galaxy chemical composition
deprecated: true
type: Concept
change note: Use instead
  comment: Galaxy abundances
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:03:04.109Z
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:03:04.137Z

RC Aurigae stars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:05:03.116Z
  comment: Emission line stars
change note: Use instead
  created: 2020-12-16T19:05:21.965Z
  creator: AAS Frey.Katie Admin
  comment: Irregular variable stars
modified: 2020-12-16T19:05:21.993Z

RR Telescopii stars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:06:23.896Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:06:23.859Z
  comment: Symbiotic binary stars

Supernova evolution
type: Concept
deprecated: true
change note: Use instead
  comment: Supernovae
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:07:59.313Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Stellar remnants
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:08:16.486Z
change note: Use instead
  comment: Stellar evolution
  created: 2020-12-16T19:08:46.419Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T19:08:46.450Z

White dwarf evolution
type: Concept
deprecated: true
change note: Use instead
  comment: Stellar evolution
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:09:57.051Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:10:49.803Z
  comment: White dwarf stars
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T19:10:49.835Z

S Vulpeculae stars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Pulsating variable stars
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:12:34.009Z
change note: Use instead
  comment: Semi-regular variable stars
  created: 2020-12-16T19:12:50.364Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T19:12:50.395Z

Beryllium abundance
deprecated: true
type: Concept
change note: Use instead
  comment: Chemical abundances
  created: 2020-12-16T19:24:30.212Z
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:24:30.250Z

Intermediate population stars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:14:11.677Z
  comment: Stellar populations
modified: 2020-12-16T19:14:11.702Z

Gravitational microlensing [Exoplanets]
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:15:13.311Z
change note: Use instead
  comment: Gravitational microlensing
  created: 2020-12-16T19:15:13.284Z
  creator: AAS Frey.Katie Admin

Polarimetry [Exoplanets]
deprecated: true
type: Concept
modified: 2020-12-16T19:16:49.912Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:16:49.875Z
  comment: Polarimetry
  creator: AAS Frey.Katie Admin

Radial velocity methods [Exoplanets]
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T19:17:50.854Z
  creator: AAS Frey.Katie Admin
  comment: Radial velocity
modified: 2020-12-16T19:17:50.883Z
contributor: AAS Frey.Katie Admin

Individual planetary nebulae
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:19:15.808Z
change note: Use instead
  created: 2020-12-16T19:19:15.778Z
  comment: Planetary nebulae
  creator: AAS Frey.Katie Admin

Individual quasars
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:20:13.141Z
change note: Use instead
  created: 2020-12-16T19:20:13.116Z
  comment: Quasars
  creator: AAS Frey.Katie Admin

Be type stars
deprecated: true
type: Concept
change note: Use instead
  created: 2020-12-16T19:21:28.576Z
  comment: Be stars
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T19:21:28.604Z
contributor: AAS Frey.Katie Admin

Exoplanet astrometry
type: Concept
deprecated: true
modified: 2020-12-16T19:22:30.421Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:22:30.396Z
  comment: Astrometry
  creator: AAS Frey.Katie Admin

Lithium abundance
deprecated: true
type: Concept
modified: 2020-12-16T19:24:02.037Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Chemical abundances
  created: 2020-12-16T19:24:01.998Z
  creator: AAS Frey.Katie Admin

Boron abundance
type: Concept
deprecated: true
modified: 2020-12-16T19:26:01.723Z
change note: Use instead
  created: 2020-12-16T19:26:01.693Z
  comment: Chemical abundances
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin

Exobiology
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:28:06.135Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Astrobiology
  created: 2020-12-16T19:28:06.109Z

Radiative processes
type: Concept
deprecated: true
modified: 2020-12-16T19:42:20.946Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Radiative processes
  created: 2020-12-16T19:42:20.913Z

Galaxy voids
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Voids
  created: 2020-12-16T19:47:18.270Z
modified: 2020-12-16T19:47:18.300Z

Intergalactic voids
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T19:46:50.525Z
change note: Use instead
  comment: Voids
  created: 2020-12-16T19:46:50.486Z
  creator: AAS Frey.Katie Admin

Cirrus vertebratus
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Atmospheric clouds
  created: 2020-12-16T19:51:02.496Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:51:09.298Z
  comment: Earth's clouds
modified: 2020-12-16T19:51:09.339Z

Cirrus uncinus
type: Concept
deprecated: true
change note: Use instead
  comment: Atmospheric clouds
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:53:17.888Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:53:24.291Z
  creator: AAS Frey.Katie Admin
  comment: Earth's clouds
modified: 2020-12-16T19:53:24.324Z

Cirrus spissatus
type: Concept
deprecated: true
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:52:49.408Z
  comment: Atmospheric clouds
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:52:55.865Z
  creator: AAS Frey.Katie Admin
  comment: Earth's clouds
modified: 2020-12-16T19:52:55.895Z

Cirrus floccus
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:52:25.125Z
  creator: AAS Frey.Katie Admin
  comment: Atmospheric clouds
change note: Use instead
  comment: Earth's clouds
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:52:31.548Z
modified: 2020-12-16T19:52:31.577Z

Cirrus castellanus
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:51:23.484Z
  comment: Atmospheric clouds
  creator: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T19:51:29.796Z
  creator: AAS Frey.Katie Admin
  comment: Earth's clouds
modified: 2020-12-16T19:51:29.831Z

Noctilucent clouds
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:53:53.448Z
  comment: Atmospheric clouds
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:53:59.502Z
  comment: Earth's clouds
modified: 2020-12-16T19:53:59.530Z

Cirrus fibratus
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Atmospheric clouds
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:51:47.012Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T19:52:00.075Z
  comment: Earth's clouds
modified: 2020-12-16T19:52:00.103Z

19521 Chaos (Kuiper Belt object)
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:16:48.525Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Classical Kuiper belt objects
  created: 2020-12-16T20:16:48.492Z

Borasisi
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T20:21:26.658Z
  comment: Classical Kuiper belt objects
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T20:21:26.686Z
contributor: AAS Frey.Katie Admin

Deucalion
deprecated: true
type: Concept
change note: Use instead
  created: 2020-12-16T20:21:37.267Z
  comment: Classical Kuiper belt objects
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T20:21:37.309Z
contributor: AAS Frey.Katie Admin

Logos
type: Concept
deprecated: true
modified: 2020-12-16T20:22:45.634Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:22:45.607Z
  creator: AAS Frey.Katie Admin
  comment: Classical Kuiper belt objects

Teharonhiawako
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Classical Kuiper belt objects
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:24:49.010Z
modified: 2020-12-16T20:24:49.043Z

Quaoar
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:24:03.786Z
  comment: Classical Kuiper belt objects
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:24:12.576Z
  comment: Plutoids
modified: 2020-12-16T20:24:12.602Z

Varuna
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:25:08.221Z
change note: Use instead
  created: 2020-12-16T20:25:08.190Z
  creator: AAS Frey.Katie Admin
  comment: Classical Kuiper belt objects

Makemake
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:23:04.871Z
  creator: AAS Frey.Katie Admin
  comment: Classical Kuiper belt objects
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:23:18.642Z
  comment: Dwarf planets
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Plutoids
  created: 2020-12-16T20:23:33.411Z
modified: 2020-12-16T20:23:33.446Z

Haumea
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Dwarf planets
  created: 2020-12-16T20:26:58.709Z
  creator: AAS Frey.Katie Admin
change note: Use instead
  comment: Plutoids
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:27:09.972Z
modified: 2020-12-16T20:27:09.998Z

Eris
type: Concept
deprecated: true
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Dwarf planets
  created: 2020-12-16T20:27:31.418Z
  creator: AAS Frey.Katie Admin
change note: Use instead
  comment: Plutoids
  created: 2020-12-16T20:27:38.185Z
  creator: AAS Frey.Katie Admin
change note: Use instead
  comment: Scattered disk objects
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:28:01.509Z
modified: 2020-12-16T20:28:01.543Z

Sedna
type: Concept
deprecated: true
change note: Use instead
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:30:56.150Z
  comment: Scattered disk objects
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:31:02.257Z
  creator: AAS Frey.Katie Admin
  comment: Plutoids
modified: 2020-12-16T20:31:02.287Z

Orcus
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:30:14.898Z
  creator: AAS Frey.Katie Admin
  comment: Plutinos
modified: 2020-12-16T20:30:14.928Z

Helium-poor stars
type: Concept
deprecated: true
modified: 2020-12-16T20:32:12.837Z
change note: Use instead
  comment: Helium-weak stars
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:32:12.810Z
contributor: AAS Frey.Katie Admin

IRAS galaxies
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Luminous infrared galaxies
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:33:59.897Z
modified: 2020-12-16T20:33:59.948Z

Minor planets
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
editorial note: Definition Provenance
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:36:41.793Z
  comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
change note: Use instead
  created: 2020-12-16T20:36:54.919Z
  creator: AAS Frey.Katie Admin
  comment: Asteroids
change note: Use instead
  comment: Small Solar System bodies
  creator: AAS Frey.Katie Admin
  created: 2020-12-16T20:37:10.086Z
modified: 2020-12-16T20:37:10.115Z

Penumbral filaments
deprecated: true
type: Concept
change note: Use instead
  comment: Sunspots
  created: 2020-12-16T20:39:35.049Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T20:39:35.083Z
contributor: AAS Frey.Katie Admin

Cometary atmospheres
deprecated: true
type: Concept
modified: 2020-12-16T20:40:38.814Z
change note: Use instead
  created: 2020-12-16T20:40:38.780Z
  creator: AAS Frey.Katie Admin
  comment: Comae
contributor: AAS Frey.Katie Admin

Cometary studies
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:41:38.980Z
change note: Use instead
  created: 2020-12-16T20:41:38.932Z
  creator: AAS Frey.Katie Admin
  comment: Comets

Yerkes classification
deprecated: true
type: Concept
modified: 2020-12-16T20:43:17.616Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Morgan-Keenan classification
  created: 2020-12-16T20:43:17.576Z

Solar M coronal region
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  comment: Solar coronal holes
  created: 2020-12-16T20:44:46.846Z
  creator: AAS Frey.Katie Admin
modified: 2020-12-16T20:44:46.875Z

Stellar M coronal regions
type: Concept
deprecated: true
change note: Use instead
  created: 2020-12-16T20:45:19.835Z
  comment: Stellar coronal holes
  creator: AAS Frey.Katie Admin
contributor: AAS Frey.Katie Admin
modified: 2020-12-16T20:45:19.865Z

Visual observation
type: Concept
deprecated: true
modified: 2020-12-16T20:46:23.926Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:46:23.896Z
  comment: Optical observation
  creator: AAS Frey.Katie Admin

Wilson-Bappu Effect
type: Concept
deprecated: true
modified: 2020-12-16T20:47:50.224Z
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:47:50.192Z
  creator: AAS Frey.Katie Admin
  comment: Absolute magnitude

Solar properties
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
change note: Use instead
  created: 2020-12-16T20:48:53.861Z
  creator: AAS Frey.Katie Admin
  comment: Solar physics
modified: 2020-12-16T20:48:53.888Z

Sociology of astronomy
deprecated: true
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2024-06-20T13:23:54.021Z
change note: Use instead
  creator: AAS Frey.Katie Admin
  comment: Ethnoastronomy
  created: 2024-06-20T13:23:54.016Z

Definition Provenance
creator: AAS Frey.Katie
comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
created: 2020-11-03T20:58:14.821Z

Definition Provenance
created: 2020-11-09T16:07:02.304Z
comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
creator: AAS Frey.Katie

Definition Provenance
comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
created: 2020-11-10T19:13:04.816Z
creator: AAS Frey.Katie

Definition Provenance
comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
creator: AAS Frey.Katie
created: 2020-11-17T19:59:22.995Z

Definition Provenance
created: 2020-11-17T20:44:18.954Z
comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri
creator: AAS Frey.Katie

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1266 (Plutinos)
created: 2020-12-03T20:18:06.796Z
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T20:28:48.348Z
comment: See instead http://astrothesaurus.org/uat/529 (Far infrared astronomy)
creator: AAS Frey.Katie Admin

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:32:41.537Z
comment: See instead http://astrothesaurus.org/uat/935 (Long period variable stars)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/944 (Luminous blue variable stars)
created: 2020-12-03T20:34:46.149Z

Deprecated concept
created: 2020-12-03T20:36:30.899Z
comment: See instead http://astrothesaurus.org/uat/1066 (Mira variable stars)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1104 (Neutrino oscillations)
created: 2020-12-03T20:38:00.447Z
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/553 (FU Orionis stars)
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:40:03.290Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1327 (R Coronae Borealis variable stars)
created: 2020-12-03T20:42:33.664Z

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:45:05.730Z
comment: See instead http://astrothesaurus.org/uat/864 (Irregular galaxies)

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1413 (RRab stars)
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:47:08.724Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1413 (RRab stars)
created: 2020-12-03T20:47:31.573Z

Deprecated concept
created: 2020-12-03T20:51:07.112Z
comment: See instead http://astrothesaurus.org/uat/634 (Gamma-ray telescopes)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1340 (Radio continuum emission)
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:52:46.605Z

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:54:14.178Z
comment: See instead http://astrothesaurus.org/uat/1410 (RR Lyrae variable stars)

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T20:55:39.639Z
comment: See instead http://astrothesaurus.org/uat/719 (Henry Draper Catalog)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/622 (Galaxy structure)
created: 2020-12-03T20:57:39.565Z

Deprecated concept
comment: Deprecated for low usage in literature.
created: 2020-12-03T20:59:24.554Z
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T21:01:07.669Z
comment: See instead http://astrothesaurus.org/uat/224 (Chemical abundances)
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T21:03:13.147Z
comment: See instead http://astrothesaurus.org/uat/1474 (Solar abundances)
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T21:04:49.665Z
comment: See instead http://astrothesaurus.org/uat/1503 (Solar magnetic fields)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: Extranous grouping concept, low usage in literatuere.
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:05:30.042Z

Deprecated concept
created: 2020-12-03T21:08:36.778Z
comment: See instead http://astrothesaurus.org/uat/1577 (Stellar abundances)
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T21:09:00.412Z
comment: See instead http://astrothesaurus.org/uat/1577 (Stellar abundances)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1577 (Stellar abundances)
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:09:23.937Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: Deprecated for low usage in literature.
created: 2020-12-03T21:10:55.823Z

Deprecated concept
created: 2020-12-03T21:12:03.057Z
creator: AAS Frey.Katie Admin
comment: Deprecated for low usage in literature.

Deprecated concept
creator: AAS Frey.Katie Admin
comment: Deprecated for low usage in literature.
created: 2020-12-03T21:14:21.146Z

Deprecated concept
comment: Deprecated for low usage in literature.
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:14:44.076Z

Deprecated concept
comment: Deprecated for low usage in literature.
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:15:12.258Z

Deprecated concept
created: 2020-12-03T21:16:36.215Z
comment: See instead http://astrothesaurus.org/uat/468 (Equatorial mount)
creator: AAS Frey.Katie Admin

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:16:58.469Z
comment: See instead http://astrothesaurus.org/uat/468 (Equatorial mount)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/468 (Equatorial mount)
created: 2020-12-03T21:18:24.106Z

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:18:40.569Z
comment: See instead http://astrothesaurus.org/uat/468 (Equatorial mount)

Deprecated concept
created: 2020-12-03T21:18:59.133Z
comment: See instead http://astrothesaurus.org/uat/468 (Equatorial mount)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: Deprecated for low usage in literature.
created: 2020-12-03T21:24:02.373Z
creator: AAS Frey.Katie Admin

Deprecated concept
comment: Deprecated for low usage in literature.
created: 2020-12-03T21:25:44.359Z
creator: AAS Frey.Katie Admin

Deprecated concept
comment: Deprecated for low usage in literature.
created: 2020-12-03T21:26:42.226Z
creator: AAS Frey.Katie Admin

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:32:49.122Z
comment: Deprecated for low usage in literature.

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:33:44.657Z
comment: Deprecated for low usage in literature.

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-03T21:35:20.927Z
comment: See instead http://astrothesaurus.org/uat/1557 (Spectroscopic binary stars)

Deprecated concept
created: 2020-12-03T21:36:52.786Z
comment: See instead http://astrothesaurus.org/uat/574 (Galaxy abundances)
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T21:37:56.221Z
creator: AAS Frey.Katie Admin
comment: Deprecated for low usage in literature.

Deprecated concept
created: 2020-12-03T21:39:45.823Z
comment: See instead http://astrothesaurus.org/uat/283 (Compact binary stars)
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T21:40:15.882Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/283 (Compact binary stars)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: Not a class of stars.
created: 2020-12-03T21:45:57.757Z

Deprecated concept
created: 2020-12-03T21:46:59.657Z
creator: AAS Frey.Katie Admin
comment: Not a class of stars.

Deprecated concept
created: 2020-12-03T21:47:48.466Z
creator: AAS Frey.Katie Admin
comment: Not a class of stars.

Deprecated concept
creator: AAS Frey.Katie Admin
comment: Deprecated for low usage in literature.
created: 2020-12-03T21:49:21.986Z

Deprecated concept
created: 2020-12-03T21:50:26.369Z
comment: Deprecated for low usage in literature.
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/672 (Gravitational microlensing)
created: 2020-12-03T21:52:23.796Z
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T22:03:32.706Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1278 (Polarimetry)

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1332 (Radial velocity)
creator: AAS Frey.Katie Admin
created: 2020-12-03T22:06:30.351Z

Deprecated concept
created: 2020-12-03T22:07:44.157Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/80 (Astrometry)

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/142 (Be stars)
created: 2020-12-03T22:08:47.032Z
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-03T22:09:46.069Z
comment: Deprecated for low usage in literature.
creator: AAS Frey.Katie Admin

Deprecated concept
comment: UAT does not provide a general concept for specific objects.
created: 2020-12-04T02:29:01.962Z
creator: AAS Frey.Katie Admin

Deprecated concept
comment: UAT does not provide a general concept for specific objects.
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:29:49.413Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/74 (Astrobiology)
created: 2020-12-04T02:31:26.739Z

Deprecated concept
created: 2020-12-04T02:34:14.292Z
comment: See instead http://astrothesaurus.org/uat/224 (Chemical abundances)
creator: AAS Frey.Katie Admin

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/224 (Chemical abundances)
created: 2020-12-04T02:34:33.761Z

Deprecated concept
created: 2020-12-04T02:34:50.923Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/224 (Chemical abundances)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/224 (Chemical abundances)
created: 2020-12-04T02:35:14.413Z

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:37:36.124Z
comment: See instead http://astrothesaurus.org/uat/1484 (Solar coronal holes)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/307 (Stellar coronal holes)
created: 2020-12-04T02:38:37.272Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/2055 (Radiative processes)
created: 2020-12-04T02:39:57.385Z

Deprecated concept
created: 2020-12-04T02:41:15.410Z
comment: See instead http://astrothesaurus.org/uat/1779 (Voids)
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-04T02:41:40.374Z
comment: See instead http://astrothesaurus.org/uat/1779 (Voids)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/2044 (Morgan-Keenan Classification)
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:44:56.961Z

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:46:35.570Z
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:54:29.345Z
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)

Deprecated concept
created: 2020-12-04T02:54:49.139Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)

Deprecated concept
created: 2020-12-04T02:55:30.709Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)

Deprecated concept
created: 2020-12-04T02:55:47.290Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:56:04.649Z
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)

Deprecated concept
created: 2020-12-04T02:56:27.283Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/258 (Earth's clouds)
created: 2020-12-04T02:56:43.545Z

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/717 (Helium-weak stars)
creator: AAS Frey.Katie Admin
created: 2020-12-04T02:58:15.562Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)
created: 2020-12-04T03:03:15.127Z

Deprecated concept
created: 2020-12-04T03:03:36.885Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)
created: 2020-12-04T03:03:52.733Z

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)
created: 2020-12-04T03:04:19.755Z
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/419 (Dwarf planets)
creator: AAS Frey.Katie Admin
created: 2020-12-04T03:04:42.162Z

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1268 (Plutoids)
created: 2020-12-04T03:05:08.604Z
creator: AAS Frey.Katie Admin

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1268 (Plutoids)
created: 2020-12-04T03:05:37.575Z

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T03:05:49.538Z
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)
created: 2020-12-04T03:06:40.316Z

Deprecated concept
created: 2020-12-04T03:07:10.814Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/250 (Classical Kuiper belt objects)

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T03:08:46.334Z
comment: See instead http://astrothesaurus.org/uat/1268 (Plutoids)

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/419 (Dwarf planets)
creator: AAS Frey.Katie Admin
created: 2020-12-04T03:08:55.123Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1268 (Plutoids)
created: 2020-12-04T03:09:16.305Z

Deprecated concept
created: 2020-12-04T03:09:25.546Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/419 (Dwarf planets)

Deprecated concept
creator: AAS Frey.Katie Admin
created: 2020-12-04T03:09:46.374Z
comment: See instead http://astrothesaurus.org/uat/1430 (Scattered disk objects)

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1430 (Scattered disk objects)
created: 2020-12-04T03:10:12.504Z
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/1268 (Plutoids)
created: 2020-12-04T03:10:33.325Z
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-04T03:12:49.974Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1266 (Plutinos)

Deprecated concept
created: 2020-12-04T03:13:09.986Z
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1266 (Plutinos)

Deprecated concept
created: 2020-12-04T03:15:09.693Z
comment: See instead http://astrothesaurus.org/uat/271 (Comae)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/280 (Comets)
created: 2020-12-04T03:15:53.058Z
creator: AAS Frey.Katie Admin

Deprecated concept
created: 2020-12-04T14:58:51.678Z
comment: See instead http://astrothesaurus.org/uat/1169 (Optical observation)
creator: AAS Frey.Katie Admin

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/946 (Luminous infrared galaxies)
created: 2020-12-04T21:05:59.186Z
creator: AAS Frey.Katie Admin

Definition Provenance
created: 2020-12-09T15:43:01.501Z
creator: AAS Frey.Katie Admin
comment: An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri

Deprecated concept
comment: See instead http://astrothesaurus.org/uat/72 (Asteroids)
creator: AAS Frey.Katie Admin
created: 2020-12-09T15:44:38.459Z

Deprecated concept
creator: AAS Frey.Katie Admin
comment: See instead http://astrothesaurus.org/uat/1469 (Small solar system bodies)
created: 2020-12-09T15:45:01.777Z

Concept label
creator: AAS Frey.Katie Admin
created: 2020-12-10T20:46:40.435Z
comment: Admittedly clunky phrasing, suggestions welcome.