# 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: 155 Search : ratio
 consideration   آگارش   âgârešFr.: considération   The act or an instance of considering.→ consider; → -tion. constant of aberration   پایا‌ی ِ بیراهش   pâyâ-ye birâhešFr.: constante d'aberration   The maximum amount of the apparent yearly displacement of a star, resulting from the → aberration of starlight. The value of the constant of aberration, κ, at J2000.0 is 20".49552. κ = (v/c) csc 1", where v is the average speed of the Earth about the Sun and c is the → speed of light in vacuum. The Earth's speed is given by: v = 2πa / [P(1 - e2)1/2], where a is the → semi-major axis of the Earth's orbit, e is the → eccentricity of the Earth's orbit, and P is the → sidereal period of the Earth. Same as → constant of annual aberration. See also → constant of diurnal aberration.→ constant; → aberration. constant of annual aberration   پایا‌ی ِ بیراهش سالانه   pâyâ-ye birâheš sâlânéFr.: constante d'aberration annuelle   Same as → constant of aberration.→ constant; → annual; → aberration. constant of diurnal aberration   پایا‌ی ِ بیراهش روزانه   pâyâ-ye birâheš ruzânéFr.: constante d'aberration diurne   The quantity 0''.3200 ρ cos φ', where ρ is the geocentric distance of the observer measured in units of → equatorial radius the Earth and φ' is the observer's → geocentric latitude. The numerical part is equal to 2πa csc1'' / (cP), where a is the equatorial radius of the Earth, P is its → sidereal period of rotation, and c is the → speed of light in vacuum.→ constant; → diurnal; → aberration. Coriolis acceleration   شتاب ِ کوریولیس   šetâb-e Coriolis (#)Fr.: accélération de Coriolis   The apparent acceleration corresponding to the → Coriolis force. It is the acceleration which, when added to the acceleration of an object relative to a rotating → reference frame and to its → centrifugal acceleration, gives the acceleration of the object relative to a fixed reference frame. Coriolis acceleration equals 2ω x v, where ω is the → angular velocity of the rotating reference frame and v is the radial velocity of a particle relative to the center of the rotating reference frame.→ Coriolis effect; → force. cosmic acceleration   شتاب ِ کیهانی   šetâb-e keyhâniFr.: accélération cosmique   → cosmic; → acceleration. deceleration   واشتاب   vâšetâb (#)Fr.: décéleration   The act or process of moving, or of causing to move, with decreasing speed. Sometimes called negative acceleration.Verbal noun of decelerate. deceleration parameter   پارامون ِ واشتاب   pârâmun-e vâšetâbFr.: paramètre de décéleration   A parameter designating the rate at which the expansion of the Universe would slow down owing to the braking gravitational effect of the matter content of the Universe. It is expressed by: q(t) = -R(t)R ..(t)/R .2(t), where R(t) represents the size of the Universe at time t. See also → expansion parameter; compare with → acceleration parameter.→ deceleration; → parameter. declaration   روناگش   runâgešFr.: déclaration   The act of declaring; announcement. 2) Something that is announced or proclaimed.Verbal noun of → declare. deflagration   تشکفت   taškaftFr.: déflagration   A rapid → chemical reaction in which the → output of → heat is enough to enable the reaction to proceed and be accelerated without input of heat from another source. The effect of a true deflagration under confinement is an → explosion. See also: → detonation; → explosion.Verbal noun of → deflagrate. demonstration   پدیش، پدیشش   padiš, padišešFr.: démonstration   1) The → act or → circumstance of proving or being → proved conclusively, as by → reasoning or a show of → evidence. 2) Something serving as → proof or supporting evidence. 3) An exhibition, as of feeling; display; → manifestation (Dictionary.com).Verbal noun of → demonstrate. deuteration   دوترش   doterešFr.: deutération   The process of introducing → deuterium into a → chemical compound.Verbal noun of → deuterate. disintegration   واپاشی، فروپاشی   vâpâši, forupâši (#)Fr.: desintégration   The breaking up of a body into fragments. For example, that of an unstable nuclei either spontaneously or as a result of bombardment by fast-moving particles, or the breaking up of a comet.Disintegration, verbal noun of disintegrate, from → dis- + → integration.Vâpâši, forupâši, from vâ-, frou-→ de- + pâši, noun of pâšidan→ disperse. diurnal aberration   بیراهش ِ روزانه   birâheš-e ruzânéFr.: aberration diurne   The aberration of a star's position due to the rotation of the Earth. Its value depends on the latitude of the observer, and is only 0''.32 in the case of an observer at the equator, where the rotational velocity is greatest.→ diurnal; → aberration. diurnal libration   هلازان ِ روزانه   halâzân-e ruzâneFr.: libration diurne   Daily geometrical libration of the Moon arising from the fact that observers at different points on the Earth see the Moon from slightly different angles. As the Moon rises in the east, you are positioned on one side of our planet, and by the time it sets in the west. Earth's rotation has carried you to the other side. This change in position produces a slight → parallax effect that adds about another 1° of libration in longitude. Two other geometrical libration are → libration in longitude and → libration in latitude. See also → physical libration.→ diurnal; → libration. duration   پایش   pâyešFr.: durée   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.). dust obscuration   تیره‌شد پت غبار   tirešod pat qobârFr.: 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. e-term of aberration   بیراهش ِ ترم ِ e   birâheš-e tarm-e eFr.: aberration elliptique   The same as → elliptic aberration.e, → elliptic; → term; → aberration. eclipse obscuration   تیره‌شد ِ خورگرفت   tirešod-e xorgereftFr.: obscuration de l'éclipse   The fraction of the Sun's area occulted by the Moon. It should not be confused with → eclipse magnitude, which is the fraction of the Sun's diameter occulted by the Moon. Eclipse obscuration may be expressed as either a percentage or a decimal fraction (e.g., 50% or 0.50) (F. Espenak, NASA).→ eclipse; obscuration, verbal noun from → obscure. electron configuration   همپیکرش ِ الکترونی   hampeykareš-e elektroniFr.: configuration électronique   Of an atom, a form of notation which shows how the electrons are distributed among the various atomic orbital and energy levels. The format consists of a series of numbers, letters and superscripts. For example, 1s2 2s2 2p3 means: 2 electrons in the 1s subshell, 2 electrons in the 2s subshell, and 3 electrons in the 2p subshell.