An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

In an exponential manner.

→ exponential; → -ly.

1) The act of setting forth information or a viewpoint.
2) Public exhibition or show.

Verbal noun of → expose.

1) The act or an instance of expressing.
2) Math.: A statement using mathematical quantities such as → scalars, → variables, → parameters, → functions, and → sets, as well as → relational and → logical  → operators such as → equality, → conjunction, → existence, → union, etc. (Steven. G. Krantz, ed., Dictionary of Algebra, Arithmetic, and Trigonometry, 2001).

→ express; → -tion.

1) An act or instance of extending; the state of being extended.
2) Physics: That property of a body by which it occupies space.
3) Math.: A field F is said to be an extension of a field K if K is a subfield of F.
4) Logic: The sum of all individuals or objects to which the comprehension of a term is applied. For example, the extension of the term "dog" is the set of all (past, present and future) dogs in the world.

Verbal noun of → extend.

Verbal noun of → externalize.

→ externalize + → -tion.

1) Dimming of light by an intervening medium (the Earth's atmosphere or the interstellar medium). It is usually due to both scattering and absorption.
2) Paleontology: The act or process of dying out or coming to an end, becoming extinct: the extinction of a species; → mass extinction.

Noun of extinct, from L. extinctus, p.p. of extinguere "to quench, wipe out," from → ex- "out" + stinguere "to quench," from PIE base *steig- "to prick, stick, pierce;" cf. Mod.Pers. tiz, tež, tig, tej, tij, tiq "sharp;" Av. tiγra- "pointed," tiγray- "arrow;" → deblur.

Xâmuši, noun of xâmuš "extinguished; silent," Mid.Pers. xâmôš "silent;" cf. Skt. amrs- "to bear patiently."

Gradient of apparent magnitude with air mass.

→ extinction; → coefficient.

In → photometric calibration, the correction for energy loss undergone by radiation due to the → atmospheric extinction. Extinction correction is done using → standard stars observed at different → airmasses.

→ extinction; → correction.

A graph representing the variation of the → interstellar extinction against → wavelength. Usually it displays the → normalized values of extinction as a function of (the → inverse) of the wavelength (in → microns). See, e.g., Sandage & Mathis, 1979, Ann. Rev. Astron. Astrophys. 17, 73.

→ extinction; → curve.

Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.

→ extinction; → star.

1) The act of extracting or the condition of being extracted.
2) Something obtained by extracting; an extract (FreeDictionary.com).

→ extract; → -tion.

The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars.

→ extragalactic; → astronomy.

Predicting the value of unknown data points by projecting a function beyond the range of known data points.

Verbal noun of → extrapolate.

The hottest variety of stars on the → horizontal branch with temperatures ranging from 20,000 to 40,000 K. EHB stars are distinguished from normal horizontal branch stars by having extremely thin, inert hydrogen envelopes surrounding the helium-burning core. They are hot, dense stars with masses in a narrow range near 0.5 Msun. These stars have undergone such extreme mass loss during their first ascent up the giant branch that only a very thin hydrogen envelope survives. Stars identified as EHB stars are found in low metallicity globular clusters as an extension of the normal HB.

→ extreme; → horizontal; → branch; → star.

Photoconductivity due to the addition of impurities or external causes.

→ extrinsic; → photoconductivity.

Šidhâzandegi, → photoconductivity; borungin, → extrinsic.

A semiconductor, such as silicon, whose responsive properties can be altered by the addition of impurities. Copper- and mercury-doped germanium are both examples of this semiconductor material.

→ extrinsic; → semiconductor.

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 (M.S.: SDE).

F referring to the Fraunhofer lines; → corona.

An empirical power-law correlation between the luminosity (L) and the velocity dispersion of stars (σ) in the center of a elliptical galaxies. The original relation can be expressed mathematically as: L ∝ σ^γ, where the index γ is observed to be approximately equal to 4, but depends on the range of galaxy luminosities that is fitted. → Tully-Fisher relation.

After the astronomers Sandra M. Faber and Robert Earl Jackson, who first noted this relation in 1976 (ApJ 204, 668); → relation.

1) To tell invented stories; create fables or stories filled with fantasy.
2) To relate an event as a fable.

→ fabulate; → -tion.

A → spiral galaxy oriented such that it is viewed from above or below. → edge-on galaxy.

→ face; → on-; → galaxy.