# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1062
 Planck time   زمان ِ پلانک   zamân-e PlanckFr.: temps de Planck   The time representing the → Planck length divided by the → speed of light. It is expressed by: tP = (Għ/c5)1/2≅ 5.4 x 10-44 s, where G is the → gravitational constant, ħ is the → reduced Planck's constant, and c is the → speed of light. At the Planck time, the mass density of the Universe is thought to approach the → Planck density.→ Planck; → time. Planck units   یکاهای ِ پلانک   yekâhâ-ye Planck (#)Fr.: unités de Planck   A set of → natural units in which the normalized units are: the gravitational constant, Planck's constant, the speed of light, the Coulomb constant, and Boltzmann's constant.→ Planck; → unit. Planck's blackbody formula   دیسول ِ سیه‌جسم ِ پلانک   disul-e siyah jesm-e PlanckFr.: formule du corps noir de Planck   A formula that determines the distribution of intensity of radiation that prevails under conditions of thermal equilibrium at a temperature T: Bv = (2hν3 / c2)[exp(hν / kT) - 1]-1 where h is Planck's constant and ν is the frequency.→ Planck; → blackbody; → formula. Planck's constant   پایای ِ پلانک   pâyâ-ye Planck (#)Fr.: constante de Planck   → Planck; → constant. Planck's radiation law   قانون ِ تابش ِ پلانک   qânun-e tâbeš-e PlanckFr.: loi du rayonnement de Planck   An equation that expresses the energy radiated per unit area per unit time per unit wavelength range by a blackbody as a function of temperature. It is expressed by → Planck's blackbody formula.→ Planck; → radiation; → law. plane   ۱) هامُن؛ ۲) تخت   1) hâmon (#); 2) taxt (#)Fr.: plan   1) (n.) a flat or level surface. 2) (adj.) Of or pertaining to planes or plane figures.1) From L. plantum "flat surface," noun use of adj. planus "flat, level, plain." 2) From L. planus, as above.1) Hâmon, variant of hâmun "plain, level ground;" Mid.Pers. hâmôn "level, flat;" Proto-Iranian *hāma-van-, from *hāma- "same, equally, even; together, with" (Mod.Pers./Mid.Pers. ham-; O.Pers./Av. ham-; cf. Skt. sam-; also O.Pers./Av. hama- "one and the same;" Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + *-van- suffix. 2) Taxt "flat;" Mid.Pers. taxtag "tablet, plank, (chess)board." plane figure   شکل ِ هامن، ~ تخت   šekl-e hâmon, ~ taxtFr.: figure plane   A two-dimensional geometric figure. The points of the figure lie entirely in a plane.→ plane; → figure. plane mirror   آینه‌ی ِ تخت   âyene-ye taxt (#)Fr.: miroir plan   A mirror whose reflective surface is neither concave nor convex.→ plane; → mirror. plane of polarization   هامن ِ قطبش   hâmon-e qotbešFr.: plan de polarisation   In a → linearly polarized light, a plane perpendicular to the → plane of vibration and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the magnetic vector (H) of the electromagnetic light wave.→ plane; → polarization. plane of rotation   هامن ِ چرخش   hâmon-e carxešFr.: plan de rotation   For a rotating object, the plane → perpendicular to the → rotation axis.→ plane; → rotation. plane of the sky   هامن ِ آسمان   hâmon-e âsmânFr.: plan du ciel   An imaginary plane that is perpendicular to the → line of sight.→ plane; → sky. plane of vibration   هامن ِ شیوش   hâmon-e šivešFr.: plan de vibration   In a → linearly polarized light, a plane perpendicular to the → plane of polarization and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the electric vector (E) of the electromagnetic light wave.→ plane; → polarization. plane polarization   قطبش ِ هامنی   qotbeš-e hâmoniFr.: polarisation plane   Same as → linear polarization.→ plane; → polarization. plane polarized light   نور ِ قطبیده‌ی ِ هامنی   nur-e qotbide-ye hâmoniFr.: lumière polarisée plane   Light exhibiting → plane polarization. Same as → linearly polarized light.→ plane; → polarized; → light. plane wave   موج ِ تخت   mowj-e taxt (#)Fr.: onde plane   A wave whose wavefronts of constant phase are infinite parallel planes normal to the direction of propagation.→ plane; → wave. plane-parallel atmosphere   هواسپهر ِ پراسو-تخت، جو ِ ~   havâsepehr-e parâsu-taxthâ, javv-e ~Fr.: atmosphère plan-parallèle   An approximation used in many stellar atmosphere models that depict the atmosphere as being only one-dimensional and bounded at the top and bottom by horizontal plane surfaces normal to the direction of gravity.→ plane; → parallel; → atmosphere. plane-parallel plate   تیغه‌ی ِ تخت-پراسو   tiqe-ye taxt-parâsuFr.: lame plan-parallèle   A piece of glass with plane parallel surfaces used to admit light into an optical system and to exclude dirt and moisture.→ plane; → parallel; → plate. planemo   پلنمو   planemoFr.: planemo   An object with a mass greater than an → asteroid, but smaller than that of a → brown dwarf.Short for planetary mass object; → planetary; → mass; → object. planet   سیاره   sayyâré (#)Fr.: planète   1) A celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit. → dwarf planet. 2) → extrasolar planet.From O.E., from O.Fr. planete (Fr. planète), from L.L. planeta (plural form planetae), from Gk. planetes (single form) "wandering," from (asteres) planetai "wandering (stars)," from planasthai "to wander," of unknown origin.Sayyâré, from Ar. saiyârat "walker, traveller." Planet Nine   سیاره‌ی ِ نه   sayyâre-ye nohFr.: Planète Neuf   A hypothetical large planet in the far outer → solar system the gravitational effects of which would explain the unexpected orbital configuration of a group of → trans-Neptunian objects (TNOs). Trujillo & Sheppard (2014) noticed a clustering of the → argument of perihelion of bodies lying beyond ~150 → astronomical unit (AU), and attributed this to a hypothetical super-Earth body lying at several hundred AUs. Batygin & Brown (2016) showed numerically and analytically how the apsidal and nodal clustering of the distant TNOs arises as a result of resonant and secular dynamical effects from a distant perturber. They identified a range of semimajor axes (400-1500 AU) and eccentricities (0.5-0.8) for which a distant planet can explain the → orbital elements of the distant TNOs. The predicted planet would have a mass of 10 Earths (approximately 5,000 times the mass of → Pluto), a diameter of four times Earth and a highly elliptical orbit with an → orbital period of approximately 15,000 years.→ planet; → nine.