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: 690
Dubhe (α Ursae Majoris)
  دبه   
dobbé (#)

Fr.: Dubhé   

The second brightest star in the constellation → Ursa Major with a → visual magnitude of about 1.8. It lies at the front of the → Big Dipper's bowl and with → Merak (Beta UMa) makes the famous → Pointers. α Ursae Majoris is a → supergiant of type K0 IIIa and has a → companion.

From Ar. al-dubb (الدب) "bear," referring to the bear in Gk. mythology.

Dobbé from Ar., as above.

ductile
  رشایند   
rešâyand

Fr.: duvtile   

Describing a substance that exhibits → ductility.

M.E., from L. ductilis, from duct(us), p.p. of ducere "to draw along," → aonduct, + -ilis "-il," a suffix of adjectives.

Rešâyand, literally "capable of becoming string, thread," from reš, as in rešté "thread, line, rope, row," rešmé "string, rope, thread," variants rasan, ras, (Gilaki) viris, related to abrišam "silk;" from reštan, risidan "to spin;" Mid.Pers. rištag "rope, string, thread;" Av. uruuaēs- "to turn around," uruuaēsa- "vortex in water;" Proto-Iranian *uris- "to turn, spin;" cf. Skt. vréśī- "an appellation of waters;" Gk. rhiknos "crooked;" Lith. rišti "tie, bind;" O.H.G. rīho "knee-bend;" âyand agent noun form of âmadan "to come; to become," → elastic.

ductility
  رشایندی   
rešâyandi

Fr.: ductilité   

The property of a metal that allows it to be elongated into wire or threads without fracture. For example, → copper and → silver are highly ductile metals.

ductile; → -ity.

Dulong-Petit law
  قانون ِ دولون-پتی   
qânun-e Dulong-Petit

Fr.: loi de Dulong et Petit   

The product of the → specific heat and → atomic weight of most solid elements at room → temperature is nearly the same. In other words, specific heat is constant for a solid and independent of temperature. Experiment shows that at moderate temperatures this law is satisfied for → crystals with rather simple structure. However, the law fails for crystals with more complex structures. More specifically the law cannot explain the variation of specific heat with temperature. The specific heat drops to zero as the temperature approaches 0 K. This behavior is explained only with the quantum theory. → Debye model.

Named after Pierre L. Dulong (1785-1838) and Alexis T. Petit (1797-1820), French chemists, who proposed the law in 1819. They collaborated in several important investigations, including studies of thermal expansion of gases and of liquids and the specific heats of substances; → law.

Dumbbell Nebula (M27, NGC 6853)
  میغ ِ دمبل   
miq-e dambel

Fr.: Nébuleuse de l'Haltère   

One of the brightest planetary nebulae; it lies in the constellation → Vulpecula at a distance of about 1000 light-years. It was discovered by Charles Messier in 1764.

Dumbbell "a short bar with weights at each end that is used for exercise," from dumb + bell. When viewed in a small telescope, the brighter portion of the nebula shows like a bipolar geometry, hence the name; → nebula.

Dambel loanword from dumbbell, as above; → nebula.

duodecennial
  دوازده‌سالی   
davâzdahsâli (#)

Fr.: duodécennal   

Consisting of twelve → years.

From L. duodecennium, from duodecim "tweleve," from duo, → two, + decem, → ten, + annus "year," → annual.

Davâzdahsâli, from davâzdah "twelve," from do, → two, + dah, → ten + sâl, → year.

duodecennial animal calendar
  گاهشمار ِ دوازده‌سالی ِ جانوری   
gâhšomâr-e davâzdahsâli-ye janevari (#)

Fr.: calendrier duodécennal   

A → lunisolar calendar in which the years are named after each of the following twelve animals: rat, ox, tiger, hare, dragon, snake, horse, sheep, monkey, cock, dog, pig. An animal presides over one year in the twelve-year cycle, which is then repeated. The calendar was/is mainly used by central Asian cultures (Khotanese, Sogdians, Buddhists, Kucheans, Mongols, and Chinese). It was also used in Iran after the Mongol invasion in the thirteenth century.

duodecennial; → animal; → calendar.

duplicate
  ۱) دوتاییدن، دوتا کردن؛ ۲) دوتاکرد   
1) dotâyidan, dotâ kardan; 2) dotâkard

Fr.: 1) faire un double de; 2) double, copie exacte   

1) To make an exact copy of.
2) A copy exactly like an original.

From L. duplicatus, p.p. of duplicare "to double," from duo, → two + plicare "to fold," → multiply.

Dotâyidan, "to double," infinitive from dotâyi, → double.

duplication
  دوتایش، دوتاکرد   
dotâyeš, dotâkard

Fr.: duplication   

An act or instance of duplicating; the state of being duplicated.

Verbal noun of → duplicate.

dust
  غبار، گرد   
qobâr(#), gard (#)

Fr.: poussière   

Tiny pieces of solid material, such as carbon and silicate grains, in the → interstellar medium that are about 0.1-1.0 micron in size. → Dust grains embedded in → molecular clouds may be significantly larger.

O.E. dust, akin to O.H.G. tunst "storm," from P.Gmc. *dunstaz, from PIE base dhem-/dhemə- "to smoke, to blow," cf. Skt. dhūmá "smoke," Mod.Pers. dam "smoke; to blow, breathe," Av. dāδmainya- "blowing up," Gk. thumiao "to fumigate, burn incense," thymos "spirit, mind, soul," L. fumus "smoke," Ossetic dymyn/dumun "to smoke, blow up," Lith. dumai "smoke."

Qobâr, from Ar.; gard "dust," Mid.Pers. gart, gard.

dust analogue
  آناگویه‌ی ِ غبار   
ânâguye-ye qobâr

Fr.: analogue de poussière   

A chemical compound produced in laboratory experiments to simulate real → interstellar dust grains and thus study them.

dust; → analogue.

dust coagulation
  ماسش ِ غبار، رچش ِ ~   
mâseš-e qobâr, roceš-e ~

Fr.: coagulation de la poussière   

A process of formation of → dust grains in → interstellar medium and → protoplanetary disks, in which randomly colliding aggregates may stick together.

dust; → coagulation.

dust devil
  دیو-باد   
div-bâd

Fr.: tourbillon de poussière   

A small but vigorous → whirlwind, usually of short duration, rendered visible by → dust, → sand, and → debris picked up from the ground (Meteorology Glossary, Amer. Meteo. Soc.). See also → dust storm, → dust whirl.

dust; → devil.

dust emission
  گسیل ِ غبار   
gosil-e qobâr

Fr.: émission des poussières   

Thermal emission in infrared from interstellar → dust grains receiving photons. Dust grains absorb ultraviolet and visible light emitted by nearby stars and re-radiate in the infrared wavelengths. Since the infrared light is of lower energy than the ultraviolet/visible light, the difference goes into heating the dust grain. Typical temperatures for interstellar grains are tens of degrees Kelvin.

dust; → emission.

dust feature
  آرنگ ِ غبار   
ârang-e qobâr

Fr.: marque de poussière, signature de ~, motif spectral de ~   

An emission or absorption mark in the spectrum of an astronomical object, the origin of which is attributed to the presence of dust in the object or on the line of sight.

dust; → feature.

dust grain
  دانه‌ی ِ غبار   
dâne-ye qobâr (#)

Fr.: grains de poussière   

A small, solid flake of → graphite and/or → silicates coated with water ice, found in the → interstellar medium or the → interplanetary medium. Dust grains are irregularly shaped with sizes from microns to Angstroms (→ very small grain; → big grain; → PAH). It is believed that the dust is mainly formed in the cool outer layers of → red giants and dispersed in the interstellar medium. In dense environments, such as → molecular clouds and around → protostars, dust grains grow due to collisions (→ grain growth). Therefore, dust grains in → protostellar disks should be larger than interstellar grains. Dust grains absorb and scatter optical and ultraviolet light and re-radiate in infrared (→ dust emission). Dust acts as a catalyst in the interstellar medium, because molecules form via reactions on the surface of dust grains.

dust; → grain.

dust lane
  باریکه‌ی ِ غبار   
bârike-ye qobâr

Fr.: bande de poussière   

A narrow, elongated structure of absorbing matter seen running over extended emission objects such as nebulae and galaxies.

dust; lane, from O.E. lane, lanu "narrow hedged-in road," cf. Du. laan "lane," O.N. lön "row of houses," of unknown origin.

Bâriké "a narrow thing," from bârik "narrow," from Mid.Pers. bārīk "narrow," Av. bāra-, as in tiži.bāra- "sharp-edged," from brāy- "to cut," Mod.Pers. bor-, boridan "to cut;" qobârdust.

dust model
  مدل ِ غبار   
model-e qobâr

Fr.: modèle de poussière   

A model of → dust grains conceived to describe the observed → interstellar extinction properties. It is characterized by the abundance of the different → chemical elements locked up in the dust, and by the → composition, → morphology, and → size distribution of its individual grains. For example, → MRN dust model.

dust; → model.

dust obscuration
  تیره‌شد پت غبار   
tirešod pat qobâr

Fr.: obscurcissement par la poussière   

The → absorption of → electromagnetic radiation from an astrophysical object by → dust grains associated with that object.

dust; → obscuration.

Tiregi, → obscuration, pat, → by; qobâr, → dust.

dust scattering
  پراکنش ِ غباری، ~ پت غبار   
parâkaneš-e qobâri, ~ pat qobâr

Fr.: diffusion par la poussière   

The scattering of → photons by → dust grains.

dust; → scattering.

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