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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<< < -es -iv -ti 21- a p abe abs abs acc acc acc act act ada adi ads aes Age Alb Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app app arb are ari art ass ast ast ast Atl ato ato Aug aut awa azi bac bal Bar Bar Bay bea Bep Bet BIC bij bin bio bir bla bla blu blu bol Boo bou Bq bre bri bub B[e cal cal can car car Cas cat cau cel cen Cer cha cha cha che chi CI cir cir cla cle clo clu co- cob 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 cov cra cri cro cry cum cur cyc d'A dar dat DC dea dec dec dec def def deh Del den dep des det deu dia dif dif dif dim dip Dir dis dis dis dis dis div dom dos dou dri Dum dus dyn dyn ear eas ecl Edd eff Ein eje ele ele ele ele eli emb emi Enc ene ens eph epo equ equ eru eth Eul eve evo exc exc exi exo exp exp ext ext Fab fai Fan fea fem fer fie fil fir fir fla flo flu foc For for fos fra fre fre fro fun g m Gal gal gal gas gau gel gen geo geo geo gho gla gno gra gra gra gra Gre Gre gro gyr had hal har Har HD hea hel hel Her Her Hic hig hip hol hor hos hov Hub hun hyd hyd Hyd hyp IC ide ill ima imp imp inc inc ind ind inf inf inf inf inj ins ins int int int int int int int int inv Io ion iro isl iso iso Jal JHK Jul jur Kel Kep kin kne L2 Lag lam Lap lar lat law Lec len Lep lib lig lin lin lin liq lit loc log lon los low lum lun lux Lyr mac mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mom moo mor mov mul mur Na nar nat nea neg Nes neu New New Nic nod non non non Nor nov nuc nul num OB obl obs occ Ock off Ohm on- ope opi opt opt orb orb ord Ori ort OSI out ove ozo pal pan par par par par pat pec pen per per per per per Pfu 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 pyr qua qua qua qua qui rad rad rad rad rad rad rak ran rat Ray rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set sha SHB sho sib sid sil sim sin sit sky slo Sne Soc sol sol sol sol son sou spa spa spe spe spe spe sph spi spo Squ sta sta sta sta ste ste ste sto str str str sub sub sub sum sup sup sup sup sur sus sym syn T d tap tec tem ten tes the the the the thi thr tid tim tip ton tor tow tra tra tra tra tri tri tru tub tur two Typ ult un- und uni uni uno upp urg UX Van var veg vel ver vib vio vir vis Voi vow wan wat wav WC wea wel whi Wil wir WNh wor X-r yel Z C zer ZZ > >>

Number of Results: 13003 Search : far
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.

grazing incidence
  فتاد ِ برمژنده   
fotâd-e barmažandé

Fr.: incidence rasante   

Light striking a surface at an angle almost perpendicular to the normal. → grazing-incidence telescope.

grazing; → incidence.

grazing occultation
  فروپوشانش ِ برمژنده   
forupušâneš-e barmažandé

Fr.: occultation rasante   

A special type of occultation that occurs when the star appears to pass tangentially on the → edge of the → Moon.

grazing; → occultation.

grazing-incidence telescope
  تلسکوپ با فتاد ِ برمژنده   
teleskop bâ fotâd-e barmažandé

Fr.: télescope à incidence rasante   

A telescope design used for focusing → extreme ultraviolet, → X-rays, and → gamma rays by means of → grazing incidence. Such short wavelengths do not reflect in the same manner as at the large incidence angles employed in optical and radio telescopes. Instead, they are mostly absorbed. To bring X-rays to a → focus, one has to use a different approach from → Cassegrain or other typical → reflecting telescopes. In a grazing-incidence telescope, incoming light is almost → parallel to the → mirror surface and strikes the mirror → surface at a very → shallow angle. Much like skipping a stone on the water by throwing it at a low angle to the surface, X-rays may be → deflected by mirrors arranged at low incidence angles to the incoming energy. Several designs of grazing-incidence mirrors have been used in various → X-ray telescopes, including → plane mirrors or combinations of → parabolic and → hyperbolic surfaces. To increase the collecting area a number of mirror elements are often nested inside one another. For example, the → Chandra X-ray Observatory uses two sets of four nested grazing-incidence mirrors to bring X-ray photons to focus onto two → detector instruments. → Bragg's law; → X-ray astronomy.

grazing incidence; → telescope.

great
  بزرگ   
bozorg (#)

Fr.: grand   

Unusual or considerable in degree, power, intensity, number, etc.

O.E. great "big, coarse, stout," from W.Gmc. *grautaz (cf. Du. groot, Ger. groß "great").

Bozorg "great, large, immense, grand, magnificient;" Mid.Pers. vazurg "great, big, high, lofty;" O.Pers. vazarka- "great;" Av. vazra- "club, mace" (Mod.Pers. gorz "mace"); cf. Skt. vájra- "(Indra's) thunderbolt," vaja- "strength, speed;" L. vigere "be lively, thrive," velox "fast, lively," vegere "to enliven," vigil "watchful, awake;" P.Gmc. *waken (Du. waken; O.H.G. wahhen; Ger. wachen "to be awake;" E. wake); PIE base *weg- "to be strong, be lively."

<< < -es -iv -ti 21- a p abe abs abs acc acc acc act act ada adi ads aes Age Alb Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app app arb are ari art ass ast ast ast Atl ato ato Aug aut awa azi bac bal Bar Bar Bay bea Bep Bet BIC bij bin bio bir bla bla blu blu bol Boo bou Bq bre bri bub B[e cal cal can car car Cas cat cau cel cen Cer cha cha cha che chi CI cir cir cla cle clo clu co- cob 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 cov cra cri cro cry cum cur cyc d'A dar dat DC dea dec dec dec def def deh Del den dep des det deu dia dif dif dif dim dip Dir dis dis dis dis dis div dom dos dou dri Dum dus dyn dyn ear eas ecl Edd eff Ein eje ele ele ele ele eli emb emi Enc ene ens eph epo equ equ eru eth Eul eve evo exc exc exi exo exp exp ext ext Fab fai Fan fea fem fer fie fil fir fir fla flo flu foc For for fos fra fre fre fro fun g m Gal gal gal gas gau gel gen geo geo geo gho gla gno gra gra gra gra Gre Gre gro gyr had hal har Har HD hea hel hel Her Her Hic hig hip hol hor hos hov Hub hun hyd hyd Hyd hyp IC ide ill ima imp imp inc inc ind ind inf inf inf inf inj ins ins int int int int int int int int inv Io ion iro isl iso iso Jal JHK Jul jur Kel Kep kin kne L2 Lag lam Lap lar lat law Lec len Lep lib lig lin lin lin liq lit loc log lon los low lum lun lux Lyr mac mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mom moo mor mov mul mur Na nar nat nea neg Nes neu New New Nic nod non non non Nor nov nuc nul num OB obl obs occ Ock off Ohm on- ope opi opt opt orb orb ord Ori ort OSI out ove ozo pal pan par par par par pat pec pen per per per per per Pfu 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 pyr qua qua qua qua qui rad rad rad rad rad rad rak ran rat Ray rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set sha SHB sho sib sid sil sim sin sit sky slo Sne Soc sol sol sol sol son sou spa spa spe spe spe spe sph spi spo Squ sta sta sta sta ste ste ste sto str str str sub sub sub sum sup sup sup sup sur sus sym syn T d tap tec tem ten tes the the the the thi thr tid tim tip ton tor tow tra tra tra tra tri tri tru tub tur two Typ ult un- und uni uni uno upp urg UX Van var veg vel ver vib vio vir vis Voi vow wan wat wav WC wea wel whi Wil wir WNh wor X-r yel Z C zer ZZ > >>