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: 716
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.

dust settling
  نیاشش ِ غبار   
niyâšeš-e qobâr

Fr.: dépose de poussières   

A process occurring in → protoplanetary disks whereby relatively large → dust grains settle to the disk midplane. These grains, with sizes from → micron to → millimeter, grow from smaller dust grains and will eventually give rise to a planetary system.

dust; → settling.

dust storm
  غبار-توفان   
qobâr-tufân

Fr.: tempête de poussière   

An unusual, frequently severe weather condition characterized by strong winds and dust-filled air over an extensive area. See also → dust devil, → dust whirl.

dust; → storm.

dust tail
  دنباله‌ی ِ غباری   
donbâle-ye qobâri (#)

Fr.: queue de poussière   

The tail of a → comet which is caused by → solar radiation pressure forcing the dust particles away from the → coma in a curved arch. Also called a → Type II tail.

dust; → tail.

dust temperature
  دمای ِ غبار   
damâ-ye qobâr

Fr.: température de poussière   

An indication of the heat amount received by → dust grains from the ambient → radiation field. Dust temperature depends on the optical properties and → sizes of grains (i.e., on the way they → absorb and → emit radiation) as well as on the → interstellar radiation field. Most of the visible and → ultraviolet radiation in galaxies from stars passes through clouds of particles and heats them. This heating leads to re-radiation at much longer wavelengths extending to the millimeter.

dust; → temperature.

dust whirl
  غبارگرد   
qobârgard

Fr.: tourbillon de poussière   

A rapidly rotating column of air (whirlwind) over a dry and dusty or shady area, carrying dust, leaves, and other light material picked up from the ground (Meteorology Glossary, Amer. Meteo. Soc.). See also → dust devil, → dust storm.

dust; → whirl.

dust-driven wind
  باد ِ غبار‌زاد   
bâd-e qobârzâd

Fr.: vent induit par poussière   

A → stellar wind generated by the action of → radiation pressure on dust grains. This occurs in the case of cool stars, such as → AGB stars, with → effective temperatures below 2500 K when the density is sufficiently large. Since dust is a very good continuum absorber, the dust grains will be radiatively accelerated outward.

dust; → drive; → wind.

duty
  هرگ   
harg (#)

Fr.: devoir   

1) Something that one is expected or required to do by moral or legal → obligation.
2) The binding or obligatory force of something that is morally or legally right; moral or legal obligation.
3) An → action or → task required by a person's position or occupation; → function (Dictionary.com).

M.E. du(e)te, from Anglo-Fr. duete, from O.Fr. deu "due, owed; proper, just," from V.L. *debutus, from L. debitus, p.p. of debere "to owe."

Harg, from Mid.Pers. harg, halg "duty, tribute; work, effort;" akin to Mod.Pers. gahulidan "to exchange, barter," → exchange; cf. Wakhi (y)ark "work, matter, business", Yaghnobi ark "work, matter, business," Yighda hor, Munji hôr(g) "work;" Proto-Ir. *harH- "to pay tribute; to barter, trade, exchange;" cognate with Gk. elein "to take (by force)," elor "loot, looty, catch;" E. to sell (Cheung 2006).

dwarf
  کوتوله   
kutulé (#)

Fr.: nain   

1) General: A person of abnormally small height owing to a pathological condition; an animal or plant much smaller than the average of its kind or species.
2) Astro.: An adjective characterizing a particular type of object, as in → dwarf star, → dwarf galaxy, → dwarf planet.
See also:
blue compact dwarf galaxy, → brown dwarf, → brown dwarfcooling, → brown dwarfdesert, → DA white dwarf, → DB white dwarf, → DC white dwarf, → DO white dwarf, → double white dwarf, → DQ white dwarf, → Draco Dwarf, → dwarf Cepheid, → dwarf elliptical galaxy, → dwarf irregular galaxy, → dwarf nova, → dwarf spheroidal galaxy, → dwarf spiral galaxy, → DZ white dwarf, → L dwarf, → M dwarf, → OB subdwarf, → red dwarf, → Sagittarius Dwarf Elliptical Galaxy, → Sagittarius Dwarf Irregular Galaxy, → Sculptor Dwarf Elliptical Galaxy, → subdwarf, → T dwarf, → tidal dwarf galaxy, → white dwarf, → white dwarf cooling track, → white dwarf crystallization, → Y dwarf.

Dwarf, from ME dwerg, dwerf, O.E. dweorg, dweorh, O.H.G. twerg "dwarf," from P.Gmc. *dweraz.

Kutulé, from kut "small, short" + Pers. diminutive suffix -ulé, → -ula. The first component kut is the base of kutâh "short, small, little," kudak "child, infant," Mid.Pers. kôtâh "low," kôtak "small, young; baby;" the Mid/Mod.Pers. kucak "small," belongs to this fammily; Av. kutaka- "little, small."

dwarf Cepheid
  کفیءوسی ِ کوتوله   
Kefeusi-ye kutulé

Fr.: céphéide naine   

An old name for a class of pulsating variable stars with small variations in amplitude, also called an AI Velae star or delta Scuti star. They lie in the lower part of the Cepheid instability strip.

dwarf; → Cepheid.

dwarf elliptical galaxy
  کهکشان ِ بیضی‌گون ِ کوتوله   
kahkašân-e beyzigun-e kutulé (#)

Fr.: galaxie elliptique naine   

A galaxy that is much smaller than other members of the elliptical class; it is designated as dE. A subtype of dwarf ellipticals is called a → dwarf spheroidal galaxy (dSph). The basic characteristics of the class are low surface brightness and smooth light distribution. They range in luminosity from that of the faintest dSph galaies MV ~ -9 to about -17. In the → Local Group there are 19 known dEs. They are very common in → galaxy clusters.

dwarf; → elliptical; → galaxy.

dwarf galaxy
  کهکشان ِ کوتوله   
kahkešân-e kutulé (#)

Fr.: galaxie naine   

A small, low luminosity galaxy that is associated with a larger spiral galaxy and may make up part of a galactic halo. There are many of them in the Local Group, and often orbit around larger galaxies such as the Milky Way and the Andromeda Galaxy. There are three main types of them: → dwarf elliptical galaxy (dE), → dwarf irregular galaxy (dI), and → dwarf spiral galaxy (dSA).

dwarf; → galaxy.

dwarf irregular galaxy
  کهکشان ِ بی‌سامان ِ کوتوله   
kahkašân-e bisâmân-e kutulé

Fr.: galaxie irrégulière naine   

An irregular galaxy that is much smaller than other irregulars. Dwarf irregulars are generally metal poor and have relatively high fractions of gas. They are thought to be similar to the earliest galaxies that populated the Universe, and are therefore important to understand the overall evolution of galaxies.

dwarf; → irregular; → galaxy.

dwarf nova
  نووای ِ کوتوله، نو‌اختر ِ ~   
novâ-ye kutulé, nowaxtar-e ~

Fr.: nova naine   

A class of → novae and → cataclysmic variables that have multiple observed → eruptions. Their prototype is → U Geminorum star. Optically, dwarf nova eruptions have amplitudes of 2-6 mag in V, a duration of a few to 20 days and a recurrence time-scale of weeks to years. Dwarf novae are thought to be → semidetached binary stars consisting of a → white dwarf  → primary accreting via → Roche lobe overflow from a → companion which is usually a → late-type, generally → main-sequence star. DN outbursts are usually attributed to the release of gravitational energy resulting from an → instability in the → accretion disk or by sudden mass transfers through the disk.

dwarf; → nova.

dwarf planet
  سیاره‌ی ِ کوتوله   
sayyâre-ye kutulé (#)

Fr.: planète naine   

A new category of → astronomical objects in the → solar system introduced in a resolution by the 26th General Assembly of the → International Astronomical Union (IAU) on August 24, 2006. The characterizing properties are as follows: 1) It is in orbit around the Sun; 2) It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a → hydrostatic equilibrium (nearly round) shape; 3) It has not "cleared the neighbourhood" around its orbit; and 4) It is not a → satellite of a → planet, or other non-stellar body. The property 3 reclassified → Pluto from a planet to a dwarf planet because it has not cleared the neighborhood of its orbit (the → Kuiper Belt). The largest known dwarf planets are: → Eris, → Pluto, → Ceres, → Makemake, and → 2015 RR245.

dwarf; → planet.

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