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
luminosity
  تابندگی   
tâbandegi (#)

Fr.: luminosité   

The → total → brightness of a star or other astronomical object. It is expressed in watts and represents the total amount of → energy that the object radiates each → second over all wavelength regions of the → electromagnetic spectrum. Because this quantity is independent of distance, it is an → intrinsic brightness.
See also:
absolute luminosity, → anomalous luminosity effect, → bolometric luminosity, → color-luminosity diagram, → Eddington luminosity, → H II region luminosity, → intrinsic luminosity, → luminosity class, → luminosity distance, → luminosity function, → luminosity problem, → luminosity-size relation, → mass-luminosity ratio, → mass-luminosity relation, → peak luminosity, → period-luminosity relation, → solar luminosity, → stellar luminosity, → wind luminosity.

Verbal noun of → luminous.

luminosity class
  رده‌ی ِ تابندگی   
rade-ye tâbandegi (#)

Fr.: classe de luminosité   

A classification of stellar spectra according to luminosity for a given → spectral type. The luminosity class is an indication of a star's → surface gravity. It is shown by a Roman numeral as follows: I (→ supergiants), II (bright → giants), III (normal giants), IV (→ subgiants), and V (→ dwarf stars, or → main-sequence stars). Luminosity classes VI (→ subdwarfs) and VII (→ white dwarfs) are rarely used. Subclasses a, b, and c are especially used for supergiants, while the most luminous → hypergiants are assigned luminosity class Ia-0.

luminosity; → class.

luminosity distance
  اپست ِ تابندگی   
apast-e tâbandegi

Fr.: distance de luminosité   

1) Distance derived by comparison of → observed and → intrinsic luminosities. If an object has a known luminosity L, and the observed flux is S, the luminosity distance is defined by DL = (L/4πS)1/2.

2) In cosmology, the → expansion of the Universe results in a diminution of the photon flux and the above equation fails. The reason is that for a homogeneous and isotropic Universe (→ Robertson-Walker metric), the luminosity decreases by a factor (1 + z)4. Therefore, the luminosity distance is related to the → angular diameter distance (DA) by: DL = (1 + z)2.DA.

luminosity; → distance.

luminosity function
  کریا‌ی ِ تابندگی   
karyâ-ye tâbandegi

Fr.: fonction de luminosité   

Number → distribution of → stars or galaxies (→ galaxy) with respect to their → absolute magnitudes. The luminosity function shows the → number of stars of a given intrinsic luminosity (or the number of galaxies per integrated magnitude band) in a given → volume of space.

luminosity; → function.

luminosity problem
  پراسه‌ی ِ تابندگی   
parâse-ye tâbandegi

Fr.: problème de luminosité   

Low-mass → protostars are about an order of magnitude less luminous than expected. Two possible solutions are that → low-mass stars form slowly, and/or protostellar → accretion is episodic. The latter accounts for less than half the missing luminosity. The solution to this problem relates directly to the fundamental question of the time required to form a low-mass star (McKee & Offner, 2010, astro-ph/1010.4307).

luminosity; → problem.

luminosity-size relation
  بازانش ِ تابندگی-اندازه   
bâzâneš-e tâbandegi-andâze

Fr.: relation luminosité-taille   

The relation between the stellar luminosity of a galaxy and its physical size. More at → mass-size relation.

luminosity; → size; → relation.

luminous
  تابان، تابشی   
tâbân (#), tâbeši (#)

Fr.: lumineux   

Radiating light or other types of electromagnetic energy.

From L. luminosus "shining, full of light," from → lumen (gen. luminis) "light," related to lucere "to shine."

Tâbân "luminous," verbal adj. of tâbidan "to shine," variants tâftan "to shine," tafsidan "to become hot," related to tâb "heat, burning; heated iron; torment," âftâb "sunshine," tâbé "frying-pan," tab "fever;" dialect of Gaz tôu-, tôwâ "to shine;" Khotanese ttav- "to be hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian tâb- "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."

Luminous Blue Variable (LBV)
  ورتنده‌ی ِ آبی ِ تابان   
vartande-ye âbi-ye tâbân

Fr.: variable bleue lumineuse   

A high-luminosity variable star, which represents a transition phase in the life of a massive star when it evolves off the main sequence to become a supernova. Only about a dozen confirmed LBVs are presently known in our Galaxy. → Hubble-Sandage variable.

luminous; → blue; → variable.

luminous efficacy
  اسکرمندی ِ تابشی   
oskarmandi-ye tâbeši

Fr.: efficacité lumineuse   

A measure indicating the ability of a light source to emit visible light using a given amount of → power. It is a ratio of the visible energy emitted to the power that goes into the bulb from the electrical line.

luminous; → efficacy.

luminous flux
  شار ِ تابشی   
šâr-e tâbeši (#)

Fr.: flux lumineux   

A measure of the rate of flow of luminous energy, evaluated according to its ability to produce a visual sensation. It is measured in lumens.

luminous; → flux.

luminous infrared galaxy (LIRG)
  کهکشان ِ فروسرخ ِ تابان   
kahkešân-e forusorx-e tâbân

Fr.: galaxie lumineuse en infrarouge   

A galaxy that emits most of its energy in the infrared and whose infrared luminosity (in the 8-1000 µm range) is more than 1011 solar luminosities. → ultraluminous infrared galaxy.

luminous; → infrared; → galaxy.

luminous intensity
  درتنویی ِ تابشی   
dartanuyi-ye tâbeši

Fr.: intensité lumineuse   

A measure of the amount of light that a point source radiates in a given direction. It is expressed by the luminous flux per unit leaving the source in the direction per unit of solid angle.

luminous; → intensity.

luminous matter
  مادّه‌ی ِ تابان   
mâdde-ye tâbân (#)

Fr.: matière lumineuse   

Ordinary baryonic matter that can emit electromagnetic radiation, as opposed to → dark matter.

luminous; → matter.

luminous red nova (LRN)
  نو‌اختر ِ سرخ ِ تابان   
now-axtar-e sorx-e tâbân

Fr.: nova rouge lumineuse   

A stellar explosion thought to be caused by the → merger of stars in a → binary system. They are characterized by a distinct red color, and a → light curve that lingers with resurgent brightness in the → infrared. The luminosity of the explosion is between that of a → supernova and a → nova.

luminous; → red; → nova

lunar
  مانگی، ماهی   
mângi (#), mahi (#)

Fr.: lunaire   

Of or pertaining to the moon.

From O.Fr. lunaire, from L. lunaris "of the moon," from luna "moon" (with capital L) "moon goddess," from *leuksna- (cf. O.C.S. luna "moon," O.Pruss. lauxnos "stars," M.Ir. luan "light, moon"), from the same source as lux, lumen "light;" cognate with Pers. ruz, → day, rowšan "bright, clear."

Mâh and mâng in Pers. are variants of the same term, the dominant form being mâh, while mâng (Av. from, see below) is used in classical literature as well as in some dialects: Tabari, Kurd. mâng, Laki, Tâti, Taeši mong, Šahmirzâdi, Sangesari mung; Mid.Pers. mâh "moon, month;" O.Pers. māha- "moon, month;" Av. māh- "month, moon," also māwngh-; cf. Skt. mās- "moon, month;" Gk. mene "moon," men "month;" L. mensis "month;" O.C.S. meseci, Lith. menesis "moon, month;" O.Ir. mi, Welsh mis, Bret. miz "month;" O.E. mona; E. moon, month; Ger. Mond, Monat; Du. maan; PIE base *me(n)ses- "moon, month."

Note: In Persian the same term, mâh, is used for two different, but related, concepts: moon and month. This was also the case for other IE languages, as shows the above etymology. However, other IE languages have evolved toward more accuracy by using different forms of the same initial term, as in E. moon / month or Ger. Mond / Monat. The Latin family uses two unrelated words, as in Fr. lune "moon" / mois "month" and Sp. luna / mes. An additional difficulty in present Pers. is that the adj. mâhi not only means "lunar" and "monthly" it also denotes "fish." For the sake of clarity and precison, this dictionary uses mângi for "lunar."

lunar calendar
  گاهشمار ِ مانگی   
gâhšomâr-e mângi

Fr.: calendrier lunaire   

A calendar that is based on the cycles of the → lunar phase and involves the → lunar month and → lunar year. For example → Islamic calendar, → Vietnamese lunar calendar.

lunar; → calendar.

lunar crater
  لاوک ِ ماه، ~ ِ مانگی، کندال ِ ~   
lâvak-e mâh, ~ mângi, kandâl-e ~

Fr.: cratère lunaire   

A → crater on the surface of the Moon.

lunar; → crater.

lunar day
  روز ِ مانگ، ~ ِ مانگی   
ruz-e mâng, ~ mângi

Fr.: jour lunaire   

The interval between two successive sunrises for an observer standing on the Moon. This is not the rotational period of the Moon, because the Moon-Earth system has moved round the Sun during that period. It is equal to the length of a → synodic month (29.5306 days).

lunar; → day.

lunar dust
  غبار ِ ماه   
qobâr-e mâh

Fr.: poussière lunaire   

A fine, powder-like dust covering the Moon's surface. → regolith. It is formed when meteoroids crash on the Moon's surface, heating and pulverizing rocks, which contain silica and metals. Since there is no wind or water to smooth rough edges, the tiny grains are sharp and jagged, and cling to nearly everything. Their main chemical compositions are SiO2 (about 45%) and Al2O3 (about 15%). The dust grains have an average size of 19 microns (40% smaller than hair).

lunar; → dust.

lunar eclipse
  ماه‌گرفت   
mâhgereft (#)

Fr.: éclipse de lune   

The → darkening of the → Moon which occurs when the Moon enters the → umbra of the → Earth's shadow. This phenomenon can occur only when the → full Moon is near one of the → lunar nodes of its → orbit around the Earth. There will be a → total eclipse if the entire Moon enters the umbra, otherwise the eclipse will be partial when the Moon is somewhat to the north or south of the node and does not cross the shadow entirely. During the eclipse the Moon looks more or less dark, depending especially on the transparency of the Earth's → atmosphere. The → refraction of Sun's light through the atmosphere sometimes gives a red color to the eclipsed Moon. Colored fringes can be seen around the shadow edge during → partial eclipses. Because an eclipse of the Moon is due to the cutting off of the Sun's light, it is visible from the entire hemisphere where the Moon is above the horizon. The maximum duration of a total lunar eclipse, when the Moon passes through the shadow centrally, is 1h 47m (M.S.: SDE).

lunar; → eclipse.

<< < -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 > >>