An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 44 Search : gas
951 Gaspra
  ۹۵۱ گسپرا   
951 Gaspra

Fr.: (951) Gaspra   

An elongated → asteroid with dimensions of about 20 × 12 × 11 km. Gaspra is classified as an → S-type asteroid and is likely composed of metal-rich silicates and perhaps blocks of pure metal. It is a member of the → Flora family. It has a → rotation period of 7.04 hours. On October 29, 1991, the → Galileo spacecraft came within 1,600 km of Gaspra. They passed each other at 8 km/s. This was the first time that a spacecraft made a → flyby of an asteroid. Gaspra was discovered by Grigoriy N. Neujamin, Ukrainian astronomer, in 1916.

Named by its discoverer for a resort on the Crimean peninsula that was visited by contemporaries such as Tolstoy and Gorky.

accreted gas
  گاز ِ فربالیده   
gâz-e farbâlidé

Fr.: gaz accrété   

The gas involved in various accretion processes, such as that fed into an → accretion disk, pulled by a compact object, or used in the mass growth of a galaxy.

accretion; → gas.

Algenib (γ Pegasi)
  الجنب   
Aljanb (#)

Fr.: Algenib   

A star which lies at the lower left-hand corner of → Pegasus. Its apparent magnitude varies between +2.80 and +2.86 over a period of 3.6 hours; → spectral type B2 IV.

Algenib, from Ar. Aljanb al-Faras "the horse's flank," from al "the" + janb "flank" + faras "horse".

barotropic gas
  گاز ِ فشارگرد   
gâz-e fešârgard

Fr.: gaz barotrope   

A gas whose density is a function solely of pressure.

barotropic; → gas.

Chaplygin gas
  گاز ِ چاپلیگین   
gâz-e Chaplygin

Fr.: gaz de Tchaplyguin   

In → dark energy models, a hypothetical fluid that can lead to cosmic acceleration at late times. In its simplest form, the Chaplygin gas has the → equation of statep = - A/ρ, where p and ρ denote the → pressure and → energy density, respectively, and A is a positive model parameter. This equation was introduced by Chaplygin (1904, Sci. Mem. Moscow Univ. Math., 21) to study the lifting force on a plane wing in aerodynamics.

Named after Sergey Chaplygin (1869-1942), Russian physicist; → gas.

coronal gas
  گاز ِ تاجی   
gâz-e tâji

Fr.: gaz coronal   

A component of the → interstellar medium in the Galaxy which appears as pockets of gas at temperatures of over one million degrees, but extremely low densities of 104 atoms per cubic centimeter. The hot coronal gas is believed to be material blown out of violent supernova explosions. It is called "coronal gas", after a similarity with the hot gas in → solar corona.

coronal; → gas.

enriched gas
  گاز ِ پرداریده   
gâz-e pordâridé

Fr.: gaz enrichi   

A gas, usually → interstellar, in which the → abundance of particular chemical or atomic species is higher than the expected values.

enriched; → gas.

gas
  گاز   
gâz (#)

Fr.: gaz   

A substance whose physical state is such that it always occupies the whole of the space in which it is contained.

Gas, from Du. gas, probably from Gk. khaos "empty space," → chaos. The term gas was coined by the Belgian physician Jean-Baptiste van Helmont (1579-1644) to designate aerial spirits.

Gâz, loanword from Fr.

gas constant
  پایا‌ی ِ گاز‌ها   
pâyâ-ye gâzhâ (#)

Fr.: constante des gaz parfaits   

For a given quantity of an → ideal gas, the product of its → pressure and the → volume divided by the → absolute temperature (R = PV/T).

gas; → constant.

gas equation
  هموگش ِ گاز   
hamugeš-e gâz

Fr.: équation des gaz   

An equation that links the pressure and volume of a quantity of gas with the absolute temperature. For a gram-molecule of a perfect gas, PV = RT, where P = pressure, V = volume, T = absolute temperature, and R = the gas constant.

gas; → equation.

gas giant
  غولپیکر ِ گازی   
qulpeykar-e gâzi (#)

Fr.: géante gazeuse   

A → giant planet composed mainly of → hydrogen and → helium with → traces of → water, → methane, → ammonia, and other hydrogen compounds. Gas giants have a small rocky or metallic core. The core would be at high temperatures (as high as 20,000 K) and extreme pressures. There are four gas giants in our solar system: → Jupiter, → Saturn, → Uranus, and → Neptune. Another category of gas giants is → ice giants. Ice giants are also composed of small amounts of hydrogen and helium. However, they have high levels of what are called "ices." These ices include methane, water, and ammonia.

gas; → giant.

gas laser
  لیزر ِ گازی   
leyzer-e gâzi

Fr.: laser à gaz   

A kind of laser where the lasing medium is a gas or a mixture of gases that can be excited with an electric discharge. The first gas laser to operate successfully was built by A. Javan and William R. Bennette at the Bell Telephone Laboratories. This laser used a mixture of helium and neon as the active medium and produced a continuous beam rather than a series of pulses. This laser operated in the infrared region of the spectrum at 1.15 micrometres. A few years later Kumar Patel developed the CO2 laser.

gas; → laser.

gas mixture
  آمیزه‌ی ِ گاز   
âmize-ye gâz

Fr.: mélange de gaz   

An aggregate of several different kinds of gases which do not react chemically under the conditions being considered. A gas mixture constitutes a homogeneous thermodynamical system.

gas; → mixture.

gas tail
  دنباله‌ی ِ گازی   
donbâle-ye gâzi

Fr.: queue de gaz   

The → ionized component of a → comet's → tail, driven nearly straight away from the → Sun Sun by the → solar wind. solar wind. Also called → ion tail, → plasma tail, and → Type I tail.

gas; → tail.

gas-poor galaxy
  کهکشان ِ کم‌گاز   
kahkešân-e kamgâz

Fr.: galaxie pauvre en gaz   

A galaxy which has a relatively low gas content. More specifically, a galaxy whose → baryonic matter is chiefly in the form of stars and has very little → interstellar matter.

gas; → poor; → galaxy.

gas-rich galaxy
  کهکشان ِ پرگاز   
kahkešân-e porgâz

Fr.: galaxie riche en gaz   

A galaxy, usually young, which has a relatively important gas content.

gas; → rich; → galaxy.

gas-to-dust ratio
  وابر ِ گاز به غبار   
vâbar-e gâz bé qobâr

Fr.: rapport gaz/poussière   

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.

gas; → dust; → ratio.

gaseous
  گازی   
gâzi (#)

Fr.: gazeux   

1) Existing in the → state of a gas.
2) Pertaining to or having the characteristics of gas.

gas; → -eous.

gaseous diffusion
  پخش ِ گازی   
paxš-e gâzi

Fr.: diffusion gazeuse   

An → isotope separation process using the different diffusion speeds of → atoms or → molecules for separation. This process is used to divide → uranium hexafluoride (UF6) into two separate streams of U-235 and U-238. Before processing by gaseous diffusion, uranium is first converted from → uranium oxide (U3O8) to UF6. The UF6 is heated and converted from a solid to a gas. The gas is then forced through a series of compressors and converters that contain porous barriers. Because uranium-235 has a slightly lighter isotopic mass than uranium-238, UF6 molecules made with uranium-235 diffuse through the barriers at a slightly higher rate than the molecules containing uranium-238. At the end of the process, there are two UF6 streams, with one stream having a higher concentration of uranium-235 than the other (EVS, a Division of Argonne National Laboratory).

gaseous; → diffusion.

gaseous nebula
  میغ ِ گازی   
miq-e gâzi

Fr.: nébuleuse gazeuse   

An → H II region, a → planetary nebula, or a → supernova remnant.

gaseous; → nebula.

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