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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Gamow barrier
  ورغه‌ی ِ گاموف   
varqe-ye Gâmof (#)

Fr.: barrière de Gamow   

In nuclear physics, a potential barrier near the surface of the nucleus that inhibits the release of alpha particles.

Gamow, after George Gamow (originally Georgiy Antonovich Gamov), the Ukrainian born theoretical physicist and cosmologist, who discovered quantum tunneling; → barrier.

Gamow condition
  بوتار ِ گاموف   
butâr-e Gamow

Fr.: condition de Gamow   

The constraint on the → baryon number density at T ~ 109 K in the early → expanding Universe. Gamow recognized that a key to the element buildup is the reaction n + p ↔ d + γ. Deuterium needs to be produced in sufficient abundance for higher elements to form, but if all → neutrons are immediately locked up into → deuterium, no higher elements can form either. The Gamow condition is expressed by nb<σv>t ~ 1, where nb is the baryon number density, σ is the cross section for the reaction at relative → velocity v, and t the expansion time-scale for the → Universe. This means that the time-scale for the above reaction is comparable to the expansion time. From this condition the baryon number density at the start of element buildup is found to be nb ~ (σvt)-1 ~ 1018 cm-3 at T = 109 K (P. J. E. Peebles, 2013, Discovery of the Hot Big Bang: What happened in 1948, arXiv.1310.2146).

Gamow barrier; → condition.

Gamow peak
  ستیغ ِ گاموف   
setiq-e Gâmof

Fr.: pic de Gamow   

In nuclear fusion, the product of the Maxwell-Boltzmann distribution with the tunnelling probability of the nuclei through their Coulomb barrier. This is the energy region where the reaction is more likely to take place: at higher energies, the number of particles becomes insignificant while at lower energies the tunnelling through the Coulomb barrier makes the reaction improbable.

Gamow barrier; → peak.

Ganymede (Jupiter III)
  گانومدس   
Gânumedes

Fr.: Ganymède   

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 × 1023 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.

In Gk. mythology, Ganymedes, a unusually beautiful prince of Troy who was abducted to Olympus by Zeus and made the cup-bearer of the gods.

gap
  گاف   
gâf (#)

Fr.: division, lacune, trou   

An empty space or interval; interruption in continuity; a break or opening, as in a fence, wall. → Encke gap.

Gap, from O.N. gap "chasm," related to gapa "to gape."

Gâf, variant kâf "split, slit," stem of kâftan, kâvidan "to split; to dig," Mid./Mod.Pers. škâf- škâftan "to split, burst," Proto-Iranian *kap-, *kaf- "to split;" cf. Gk. skaptein "to dig;" L. cabere "to scratch, scrape," P.Gmc. *skabanan (Goth. skaban; Ger. schaben; E. shave). PIE base *(s)kep- "to cut, to scrape, to hack."

Garnet star
  ستاره‌ی ِ نارسنگ   
setâre-ye nârsang

Fr.: étoile Grenat   

A variable → red supergiant star of → spectral type M2 Ia in the → constellation → Cepheus. Also called → Mu Cephei. Its → apparent magnitude is usually about 4.5 and varies from 3.6 to 5.1. It is also a → triple star.

Garnet "a deep-red color," from the more or less transparent, usually red, silicate mineral that has a vitreous luster. So named by William Herschel from its unusual deep reddish tint. From O.Fr. grenat "garnet," from M.L. granatum, originally an adj., "of dark red color," probably abstracted from pomegranate, from M.L. pomum granatum "apple with many seeds," from pome "apple, fruit" + grenate "having grains."

Nârsang, from nâr, from anâr "pomegranate," from Mid.Pers. anâr "pomegranate" + sang, → stone.

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 metallicity
  فلزیگی ِ گاز   
felezigi-ye gâz

Fr.: métallicité de gaz   

The metallicity derived from observations of the gas component of a galaxy. It is mainly measured from optical → emission lines using primarily oxygen abundances. The gas → metallicity is one of the most important tools to investigate the evolutionary history of galaxies. The reason is that the gas metallicity of galaxies is basically determined by their star-formation history. Recent observational studies has allowed the investigation of the gas metallicity even in → high redshift beyond z = 1, such as → Lyman break galaxies, submillimeter-selected high-z galaxies, and so on. Such observational insights on the metallicity evolution of galaxies provide constraints on the theoretical understandings of the formation and the evolution of galaxies.

gas; → metallicity.

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.

<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>