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: 692
double-degenerate binary system
  راژمان ِ درین ِ دوبار واگن   
râžmân-e dorin-e dobâr vâgen

Fr.: système binaire doublement dégénéré   

A system of evolved → binary stars in which both → components have ejected their envelopes and evolve toward → white dwarf stage. So far a half dozen double-degenerate → binary systems are known, for example Henize 2-248 (M. Santander-Garcia et al., 2015, 518, 5).

double; → degenerate; → binary; → system.

double-diffusive convection
  همبز ِ دوپخشی   
hambaz-e do paxši

Fr.:   

An instability involving two layers of fluid with opposite gradients of properties. Same as → fingering instability. See also → salt finger. Double-diffusive instabilities commonly occur in any astrophysical fluid that is stable according to the → Ledoux criterion, as long as the entropy and chemical stratifications have opposing contributions to the dynamical stability of the system. They drive weak forms of convection, and can cause substantial heat and compositional → mixing. Two cases can be distinguished. In fingering convection, entropy is stably stratified (∇ - ∇ad < 0), but chemical composition is unstably stratified (∇μ < 0); it is often referred to as → thermohaline convection by analogy with the oceanographic context in which the instability was first discovered. In oscillatory double-diffusive convection, entropy is unstably stratified (∇ - ∇ad > 0), but chemical composition is stably stratified (∇μ > 0); it is related to semiconvection, but can occur even when the → opacity is independent of composition (P. Garaud, 2014, arXiv:1401.0928).

double;→ diffusive; → system.

double-lined binary
  دورین ِ دوخطه   
dorin-e doxatté

Fr.: binaire à double raies   

A → spectroscopic binary in which the → spectral lines of both stars are seen and the lines are alternatively double and single. Same as → SB2 binary. See also: → single-lined binary.

double; → line; → binary

double-lined eclipsing binary
  دورین ِ گرفتی ِ دوخطه   
dorin-e gerefti-ye doxatté

Fr.: binaire à éclipse à double raies   

A → double-lined spectroscopic binary whose → light curve is typical of an → eclipsing binary.

double; → line; → eclipsing; → binary.

double-lined spectroscopic binary
  درین ِ دوخطه‌ی ِ بیناب‌نماییک   
dorin-e doxatte-ye binâbnemâyik

Fr.: binaire spectroscopique à double raies   

Same as → double-lined binary.

double; → line; → spectroscopic; → binary.

double-lobed radio source
  خن ِ رادیویی با لپ ِ دوتایی   
xan-e râdioyi bâ lap-e dotâyi

Fr.: radio source à double lobe   

A → galaxy that emits radio energy from two regions located on opposite sides of the galaxy.

double; → lobe; → radio; → source.

double-slit experiment
  آزمایش ِ شکاف ِ دوتایی   
âzmâyeš-e šekâf-e dotâyi (#)

Fr.: expérience de double fente   

An experiment of → diffraction and → interference of two light beams using a → double slit; → Young's experiment.

double; → slit; → experiment.

doublet
  دوتایه   
dotâyé

Fr.: doublet   

A pair of forbidden spectral lines of the same atom arising from a common upper excitation level, for example [O III] λ 5007 and [O III] λ 4959, [N II] λ 6584 and [N II] λ 6548, and [S II] λ 6717, [S II] λ 6731.
A pair of associated lines arising from transitions having a common lower energy level in a spectrum characteristic of the alkali metals.

From O.Fr. doublet, from → double + -et diminutive suffix.

Dotâyé, from dotâdouble + -(y)é nuance suffix.

doubly
  دوبار-، دو-، دوتایی   
dobâr-, dv-, dotâyi

Fr.: double, à ~   

1) To a double measure or degree.
2) In a double manner. → doubly convex, → doubly ionized, → doubly refracting crystal.

double; → -ly (; → twice).

doubly convex
  دو-کوژ   
do-kuž

Fr.: double-convexe   

Describing a → lens which is → convex on both sides.

doubly; → convex.

doubly ionized
  دوبار یونیده   
dobâr yonidé (#)

Fr.: deux fois ionisé   

An atom that has lost two of its external electrons, for example O++ ([O III]).

doubly; → ionized.

doubly refracting crystal
  بلور ِ شکست ِ دوتایی   
bolur-e šakst-e dotâyi

Fr.: cristal à double réfraction   

A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray.

doubly; → refracting; → crystal.

down
  پایین   
pâyin (#)

Fr.: en bas, vers le bas   

Toward or in a lower physical position.
See also: → download, → downgrade, → upload, → downsizing, → meltdown, → overload, → spin-down, → top-down structure formation.

M.E. doun, from O.E. dune "downward," short for adune, ofdune, from a-, of "off, from" + dune "hill."

Pâyin "bottom, below; at the foot of," from pâ(y) "foot; step;" Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-.

downgrade
  فرود-پداک، فرود-پداکیدن   
forud-padâk, forud-padâkidan

Fr.: déclasser, dévaloriser   

1) A downward slope, especially of a road.
2) To assign to a lower status; to minimize the importance of (Dictionary.com).

down; → grade.

download
  ۱) بارگرفتن؛ ۲) بارگیری   
1) bârgereftan; 2) bârgiri (#)

Fr.: 1) télécharger; 2) téléchargement   

1) To transfer data from any other computer to one's computer.
2) The act of downloading.

down; → load.

Bârgereftan, literally "to take load," from bâr, → load, + gereftan "to take," → receiver; bârgiri, verbal noun of bârgereftan.

downsizing
  بزرگ-به-کوچک   
bozorg-bé-kucak

Fr.:   

A scenario of galaxy formation whereby massive galaxies formed earlier in the history of the → Universe (i.e. at high → redshifts) and completed their → star formation process more rapidly than low-mass galaxies. This scenario contrasts with what might be expected from simple → hierarchical structure formation scenarios, which predict that large galaxies formed in more recent times through the → merging of small galaxies.

Downsizing, first suggested by Cowie et al. (1996, AJ 112, 839), from downsize (v.), is a new sense for this term. Its current main meaning in non astrophysical contexts is "to make in a smaller size, or become smaller in size (in particular in economic vocabulary, by reductions in personnel)," from → down + → size.

Bozorg-bé-kucak, literally "large to small," from bozorg, → large, + "to" + kucak, → small.

downstream
  فروداب   
forudâb (#)

Fr.: en aval   

1) With or in the direction of the current of a stream. → upstream.
2) Of or pertaining to the latter part of a process or system.

down; → stream.

Forud, → incidence; water, → water.

DQ white dwarf
  سفید‌کوتوله‌ی ِ DQ   
sefid kutule-ye DQ

Fr.: naine blanche DQ   

A → white dwarf whose spectrum shows carbon features of any kind.

D short for → dwarf; Q a convention; → white.

Draco
  اژدها   
eždahâ (#)

Fr.: Dragon   

The Dragon. A large constellation that winds around the north → celestial pole, appearing to encircle → Ursa Minor. The north → ecliptic pole also lies within Draco. Abbreviation: Dra, genitive form: Draconis.

O.Fr. dragon, from L. draco "serpent, dragon," from Gk. drakon "serpent, seafish," from drak-, strong aorist stem of derkesthai "to see clearly," perhaps literally "the one with the (deadly) glance," cf. Av. darəs- "to look," huuarə.darəsa- "having the appearance of the sun," Skt. darś- "to see, appear, look, show," dárśya- "worthy of being seen;" PIE base *derk- "to look."

Eždahâ, from Mid.Pers. aždahâg, ažidahâk, from Av. aži.dahāka- "the name of an evil king in the Iranian mythology," from aži- "serpent; dragon, monster" (Mid.Pers. až, âž, aži), cf. Skt. áhi- "snake, adder," Gk. ékhis, óphis "snake," L. anguis "snake," Arm. auj, Russ. , Lith. angis; PIE base *angw(h)i- "snake, worm." The etymology of the second component, Av. dahāka-, is a matter of discussion. It is probably related to dahaka- "stinging, tormenting," from dah- "to sting, to do harm."

Draco Dwarf
  کوتوله‌ی ِ اژدها   
kutule-ye eždahâ

Fr.: Naine du Dragon   

A dwarf elliptical galaxy that is a satellite of our Galaxy and lies at a distance of about 250,000 light-years from the Galactic center. Its diameter is only about 3,500 light-years, and its absolute magnitude -8.6, making it the least luminous galaxy known.

Draco; → dwarf.

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