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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12948 Search : far
gravitationally bound
  گرانشانه بندیده   
gerânešâné bandidé

Fr.: gravitationnellement lié   

Objects held in orbit about each other by their → gravitational attraction. Such objects are part of a → bound system.

gravitational; → bound.

gravitino
  گراویتینو   
gerâvitino (#)

Fr.: gravitino   

A hypothetical force-carrying particle predicted by supersymmetry theories. The gravitino's spin would be 1/2; its mass is unknown.

From gravit(on) + (neutr)ino.

graviton
  گراویتون   
gerâviton (#)

Fr.: graviton   

A hypothetical elementary particle associated with the gravitational interactions. This quantum of gravitational radiation is a stable particle, which travels with the speed of light, and has zero rest mass, zero charge, and a spin of ± 2.

From gravit(y), → gravity + → -on a suffix used in the names of subatomic particles.

gravity
  گرانی   
gerâni (#)

Fr.: gravité   

1) The apparent force of → gravitation on an object at or near the surface of a star, planet, satellite, etc.
2) Same as → gravitation and → gravitational interaction.

From L. gravitatem (nom. gravitas) "weight, heaviness," from gravis "heavy," from PIE base *gwrə- "heavy" (cf. Mod.Pers. gerân "heavy;" Av. gouru- "heavy;" Skt. guru- "heavy, weighty, venerable;" Gk. baros "weight," barys "heavy;" Goth. kaurus "heavy").

Gerâni, noun of gerân "heavy, ponderous, valuable," from Mid.Pers. garân "heavy, hard, difficult;" Av. gouru- "heavy" (in compounds), from Proto-Iranian *garu-; cognate with gravity, as above.

gravity assist
  یاری ِ گرانشی   
yâri-ye gerâneši

Fr.: gravidéviation   

An important astronautical technique whereby a → spacecraft takes up a tiny fraction of the → orbital energy of a planet it is flying by, allowing it to change → trajectory and → speed. Since the planet is not at rest but gravitating around the Sun, the spacecraft uses both the orbital energy and the gravitational pull of the planet. Also known as the slingshot effect or → gravitational slingshot. More specifically, as the spacecraft approaches the planet, it is accelerated by the planet's gravity. If the spacecraft's velocity is too low, or if it is heading too close to the planet, then the planet's → gravitational force will pull it down to the planet. But if its speed is large enough, and its orbit does not bring it too close to the planet, then the gravitational attraction will just bend the spacecraft's trajectory around, and the accelerated spacecraft will pass rapidly by the planet and start to move away. In the absence of other gravitational forces, the planet's gravity would start to slow down the spacecraft as it moves away. If the planet were stationary, the slow-down effect would be equal to the initial acceleration, so there would be no net gain in speed. But the planets are themselves moving through space at high speeds, and this is what gives the "slingshot" effect. Provided the spacecraft is traveling through space in the same direction as the planet, the spacecraft will emerge from the gravity assist maneuver moving faster than before.

gravity; assist, from M.Fr. assister "to stand by, help, assist," from L. assistere "assist, stand by," from → ad- "to" + sistere "to cause to stand," from PIE *siste-, from *sta- "to stand" (cognate with Pers. istâdan "to stand").

Yâri "assistance, help; friendship," from yâr "assistant, helper, friend," from Mid.Pers. hayyâr "helper," hayyârêh "help, aid, assistance," Proto-Iranian *adyāva-bara-, cf. Av. aidū- "helpful, useful."

gravity brightening
  روشنش ِ گرانشی   
rowšaneš-e gerâneši

Fr.: embrillancement gravitationnel   

gravity darkening.

gravity; → brightening.

gravity darkening
  تاریکش ِ گرانشی   
târikeš-e gerâneši

Fr.: assombrissement gravitationnel   

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. See also → gravity darkening exponent. Recent theoretical work (Espinosa Lara & Rieutord, 2011, A&A 533, A43) 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.

gravity; → darkening

gravity darkening coefficient
  همگر ِ تاریکش ِ گرانشی   
hamgar-e târikeš-e gerâneši

Fr.: coefficient de l'assombrissement gravitationnel   

According to the → von Zeipel theorem, the emergent flux, F, of total radiation at any point over the surface of a rotationally or tidally distorted star in → hydrostatic equilibrium varies proportionally to the local gravity acceleration: F ∝ geffα, where geff is the → effective gravity and α is the gravity darkening coefficient. See also the → gravity darkening exponent.

gravity; → darkening; → coefficient.

gravity darkening exponent
  نمای ِ تاریکش ِ گرانشی   
nemâ-ye târikeš-e gerâneši

Fr.: exposant de l'assombrissement gravitationnel   

The exponent appearing in the power law that describes the → effective temperature of a → rotating star as a function of the → effective gravity, as deduced from the → von Zeipel theorem or law. Generalizing this law, the effective temperature is usually expressed as Teff∝ geffβ, where β is the gravity darkening exponent with a value of 0.25. It has, however, been shown that the relation between the effective temperature and gravity is not exactly a power law. Moreover, the value of β = 0.25 is appropriate only in the limit of slow rotators and is smaller for fast rotating stars (Espinosa Lara & Rieutord, 2011, A&A 533, A43).

gravity; → darkening; → exponent.

gravity mode
  ترز ِ گرانی، مد ِ ~   
tarz-e gerâni, mod-e ~

Fr.: mode gravité   

Same as → g mode

gravity; → mode.

gravity wake
  کل ِ گرانی   
kel-e gerâni

Fr.: sillage de gravité   

Transient → streamers which form when → clumps of particles begin to collapse under their own → self-gravity but are sheared out by → differential rotation. This phenomenon is believed to be the source of → azimuthal asymmetry in → Saturn's → A ring (Ellis et al., 2007, Planetary Ring Systems, Springer).

gravity; → wake.

gravity wave
  موج ِ گرانی   
mowj-e gerâni

Fr.: onde de gravité   

1) A wave that forms and propagates at the free → surface of a body of → fluid after that surface has been disturbed and the fluid particles have been displaced from their original positions. The motion of such waves is controlled by the restoring force of gravity rather than by the surface tension of the fluid.
2) Not to be confounded with → gravitational wave.

gravity; → wave.

gravo-turbulence
  گرانی-آشوبناکی   
gerâni-âšubnâki

Fr.: gravo-turbulence   

The interplay between supersonic turbulence and self-gravity in star forming gas.

Gravo-, from grav-, from → gravity + epenthetic vowel -o- + → turbulence.

gray
  خاکستری   
xâkestari (#)

Fr.: gris   

(n.) A color between white and black. (adj.) Having a neutral hue.

M.E., O.E. græg, from P.Gmc. *græwyaz; cf. O.N. grar, O.Fris. gre, Du. graw, Ger. grau; Frank. *gris, Fr. gris.

Xâkestari, "ash-colored," from xâkestar "ashes," from Mid.Pers. *xâkâtur, from xâk "earth, dust" + âtur "fire," varaint âtaxš (Mod.Pers. âtaš, âzar, taš), from Av. ātar-, āθr- "fire," singular nominative ātarš-; O.Pers. ātar- "fire;" Av. āθaurvan- "fire priest;" Skt. átharvan- "fire priest;" cf. L. ater "black" ("blackened by fire"); Arm. airem "burns;" Serb. vatra "fire;" PIE base *āter- "fire."

gray (Gy)
  گری   
gray

Fr.: gray   

An SI unit of absorbed radiation dose. One gray is equivalent to an energy absorption of 1 → joule/kg. It has replaced the → rad (rd), an older standard. One gray is equivalent to 100 rad.

Named for Louis Harold Gray (1905-1965), British radiologist and the pioneer of use of radiation in cancer treatment.

gray atmosphere
  جّو ِ خاکستری، هواسپهر ِ ~   
javv-e xâkestari, havâsepher-e ~

Fr.: atmosphère grise   

A simplifying assumption in the models of stellar atmosphere, according to which the absorption coefficient has the same value at all wavelengths.

gray; → atmosphere.

gray body
  جسم ِ خاکستری   
jesm-e xâkestari (#)

Fr.: corps gris   

A hypothetical body which emits radiation at each wavelength in a constant ratio, less than unity, to that emitted by a black body at the same temperature.

gray; → body.

graze
  برمژیدن   
barmažidan (#)

Fr.: raser, frôler, effleurer   

To touch or rub lightly in passing.

Perhaps special use of graze "to feed on grass," from M.E. grasen, O.E. grasian.

Barmažidan, from Choresmian parmž "to touch, to rub," variants barmajidan, majidan, parmâsidan, Mid.Pers. pahrmâh- "to touch, to feel;" ultimately from Proto-Ir. *pari-mars-, from *Hmars-, *Hmarz- "to touch, rub, wipe;" probably related to marz "border, frontier," mâlidan "to rub, polish."

grazer
  برمژنده   
barmžandé

Fr.: rasant   

A thing that grazes.

Agent noun of → graze.

grazing
  ۱) برمژنده؛ ۲) برمژ   
1) barmažandé; 2) barmaž

Fr.: 1) rasant; 2) rasage, frôlement, effleurement   

1) Describing something that grazes. → grazing angle, → grazing occultation.
2) The act of touching or rubbing lightly in passing.

graze; → -ing.

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu 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 coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>