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: 464
luminosity distance
  دورای ِ تابندگی   
durâ-ye tâbandegi

Fr.: distance de luminosité   

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. For very distant galaxies, spatial curvature is important and the luminosity distance differs from other measures of distance.

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.

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 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.

lunar ecliptic limit
  حد ِ هورپهی ِ ماه   
hadd-e hurpehi-ye mâh

Fr.: limite écliptique de la Lune   

The farthest distance from a → lunar orbit node within which, if the Moon happens to be at full, a lunar eclipse may occur. The lunar ecliptic limit extends about 12° on each side of the node.

lunar; → ecliptic; → limit.

lunar exosphere
  برون‌سپهر ِ ماه   
borun-sepehr-e mâh

Fr.: exosphère lunaire   

An extremely thin gathering of gas surrounding the → Moon. It is made up of → atoms and → ions generated at the Moon's surface by interaction with → solar radiation, → plasma in the Earth's → magnetosphere, or → micrometeorites.

lunar; → exosphere.

lunar geology
  زمین‌شناسی ِ ماه   
zaminšenâsi-ye mâh

Fr.: géologie lunaire   

The study of the → Moon's → crust, → rocks, strata (→ stratum), etc.

lunar; → geology.

lunar highland
  کوهسار ِ مانگی   
kuhsâr-e mângi

Fr.: hauts plateaux lunaires   

A light color area on the → Moon, as contrasted with → lunar maria. Also called terra.

lunar; → highland.

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