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

Primary star of the → Delta Scorpii system.

Dschubba, from Ar. Al-Jabhah (الجبهه) "the forehead" Scorpion). The name was officially adopted by the → International Astronomical Union's Working Group on Star Names on 21 August 2016.

Of, pertaining to, or noting two; having a twofold, or double, character or nature.

From L. dualis, from duo "two."

Dogâné, from do "two," cognate with duo + -gân plurality suffix + -é nuance suffix.

The outcome of a → merger process between two galaxies, each with its own central → supermassive black hole (SMBH), resulting in a remnant galaxy hosting two SMBHs. Simulations of → galaxy mergers show there should be lots of dual → active galactic nuclei (AGN) visible at less than 10 kpc separations. As of 2015 more than 100 known dual supermassive black holes have been found. See also → binary supermassive black hole.

→ dual; → supermassive; → black; → hole.

1) Philo.: The doctrine, as opposed to idealism and materialism, that reality consists of two basic types of substance usually taken to be mind and matter or two basic types of entity, mental and physical.
2) The state of being twofold or double. → dualism, → pluralism (Dictionary.com).

→ dual; → -ism.

The quality or character of being twofold, as the → wave-particle duality.

M.E dualitie, from L.L. dualitas.

Dogânegi, from dogânag + -i.

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.

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.

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.

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.

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.

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.

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.

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.

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

Verbal noun of → duplicate.

The ability to withstand damage or decay.

→ durable; → -ity.

Capable of lasting, enduring; withstanding deterioration.

→ duration; → -able.

Continuance in time; a period of existence or persistence; length of time during which anything continues.

Noun of action from L. durare "to harden," → during.

Pâyeš, noun of action from pâyidan, → last (v.).

In the course of, in the time of, throughout the continuance of.

M.E. Duryng, durand, pr.p. of duren "to last, endure, continue, be or exist," from O.Fr. durer, from L. durare "to harden," from durus "hard;" PIE root *deru- "be firm, solid, steadfast."

Tarpây, literally "lasting over time," from tar- "through, across, over time," variant tarâ-, → trans-, + pây present stem and agent noun of pâyidan, → last (v.).

The time of day immediately following → sunset which is partial darkness between day and night.

Back formation from M.E. dosk, duske "dusky," from O.E. dox "dark-haired, dark."

Šâmgâh, from šâm "evening, evening meal" + gâh "time." The first component, šâm, from Mid.Pers. šâm "evening meal, supper," from Av. xšāfnya- "evening meal," from Av. xšap-, xšapā-, xšapan-, xšafn- "night" (O.Pers. xšap- "night;" Mid.Pers. šap; Mod.Pers. šab "night"); cf. Skt. ksap- "nigh, darkness;" Hitt. ispant- "night." The second component gâh "time;" Mid.Pers. gâh, gâs "time;" O.Pers. gāθu-; Av. gātav-, gātu- "place, throne, spot;" cf. Skt. gâtu- "going, motion; free space for moving; place of abode;" PIE *gwem- "to go, come."

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.