An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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

→ dust; → analogue.

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

→ dust; → coagulation.

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.

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.

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.

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.

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;" qobâr→ dust.

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.

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

→ dust; → obscuration.

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

The scattering of → photons by → dust grains.

→ dust; → scattering.

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.

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.

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.

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.

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.

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.

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).

A → braneworld theory in which the → space-time is locally embedded in a five dimensional space, the → bulk, and has as a key aspect leakage of gravitational energy into the bulk. More specifically, the → graviton is pinned to a four-dimensional braneworld by intrinsic curvature terms induced by quantum matter fluctuations. But as it propagates over large distances, the graviton eventually evaporates off the brane into an infinite volume, five-dimensional Minkowski bulk. Therefore, the DGP braneworld theory is a model in a class of theories in which gravity deviates from conventional → General Relativity not at short distances, but rather at long distances. This means that at those distances General Relativity cannot correctly describe gravitational interactions. This model has various cosmologically interesting features. Particularly in the model with five dimensional bulk, the → accelerating expansion of the Universe at late epoch is realized without introducing the → cosmological constant (see, e.g., A. Lue, 2002, arxiv.0208169, T. Tanaka, 2003, arXiv.0305031).

G. Dvali, G. Gabadadze and M. Porrati, 2000, Phys. Lett. 485B, 208.

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, → dwarf starburst 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."

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.