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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 simple fraction   برخه‌ی ِ ساده   barxe-ye sâdéFr.: fraction simple   A fraction in which the → numerator and → denominator are positive → integer numbers. Compare → compound fraction.→ simple; → fraction. simple harmonic motion   جنبش ِ هماهنگ ِ ساده   jonbeš-e hamâhang-e sâdéFr.: mouvement harmonique   The motion of a body subjected to a restraining force which is directly proportional to the displacement from a fixed point in the line of motion. The equation of simple harmonic motion is given by x = A sin(ωt + θ0), where x is the body's displacement from equilibrium position, A is the → amplitude, or the magnitude of harmonic oscillations, ω is the → angular frequency, t is the time elapsed, and θ0 is the → initial phase angle.→ simple; → harmonic; → motion. simple harmonic oscillator   نوشگر ِ هماهنگ ِ ساده   navešgar-e hamâhang-e sâdéFr.: oscillateur harmonique simple   An oscillator whose force is proportional to its extension, according to → Hooke's law. The way the oscillator moves is called → simple harmonic motion.→ simple; → harmonic; → oscillator. simple population   پرینش ِ ساده   porineš-e sâdéFr.: population simple   A set of stars resulting from a spatially (≤ few pc) and temporally (≤ Myr) correlated star formation event.→ simple; → population. simplification   ساده‌کرد، ساده‌شد   sâde-kard, sâde-šodFr.: simplification   The act of simplifying, or the fact of being simplified.Verbal noun of → simplify. simulation   مانندش، همانندسازی   mânandeš, hamânand sâziFr.: simulation   The construction of a mathematical model to reproduce the characteristics of a phenomenon, system, or process, often using a computer, in order to infer information or solve problems.Verbal noun of → simulate. single-dish observation   نپاهش ِ تک-جام   nepâhešè-e tak-jâmFr.: observation avec antenne uinique   A radio astronomical observation which uses only one antenna, in contrast to interferometric observations.→ single; → dish; → observation. singly ionized atom   اتم ِ یکبار یونیده   atom-e yekbâr yonidéFr.: atome une fois ionisé   An atom that has lost one electron and has become a positive ion.→ single; → ionized; → atom. singly ionized carbon   کربون ِ یکبار یونیده   Fr.: carbone une fois ionié   A carbon atom → singly ionized by a photon of energy 11.3 eV. The ion C+ emits a → fine-structure line (2P3/2→ 2P1/2) at 157.7 μm when excitation conditions are satisfied (critical density ~ 3 x 103 cm-3). In → photodissociation regions, [C II] 157.7 μm is a major cooling line for regions exposed to significant → far ultraviolet (FUV) photon fluxes. In Galactic → H II regions, as well as in the central regions of external galaxies, the luminosity of the [C II] line is typically ~ 0.05-0.5% of the FUV luminosity and correlates well with → carbon monoxide (CO) line intensities.→ single; → ionized; → carbon. singular solution   لویش ِ تکین   luyeš-e takinFr.: solution singulière, ~ particulière   Of partial differential equations, the solution which cannot be obtained from the general solution by particular choice of arbitrary functions. → general solution; → particular solution.→ singular; → solution. siphon   سیفون   sifon (#)Fr.: siphon   A ∩-shaped tube with unequal arms that is used to move a liquid from one level to a lower level via a third level higher than either. Once the short arm is filled, for example, by suction, the liquid flows down in the long arm under the action of gravity due to mass excess in it.From Fr. siphon, from L. sipho (genitive siphonis), from Gk. siphon "pipe, tube," of unknown origin. site selection   گزینش ِ سیت   gozineš-e sitFr.: sélection de site   The process of choosing a site for an astronomical observatory based on meteorology, seeing conditions, and access to the site.→ site; → selection. situation   سیتش   sitešFr.: situation   1) The manner of being placed with respect to surroundings. 2) Momentary state; a set of circumstances.Verbal noun of → situate. sky subtraction   زیرکرشش ِ آسمان   zirkaršeš-e âsmânFr.: soustraction de ciel   The act or instance of removing the contribution of non-related, intervening foreground light to the object.→ sky; → subtraction. slepton   اسلپتون   sleptonFr.: slepton   In → supersymmetry theories, a hypothetical → boson super-partner of a → lepton. See also → squarks from → supersymmetry; → lepton. slow neutron   نوترون ِ آهسته   notron-e âhesté (#)Fr.: neutron lent   A neutron whose kinetic energy does not exceed about 10 electron-volts. Also called → thermal neutron.→ slow; → neutron. SMASS classification   رده‌بندی ِ SMASS   radebandi-ye SMASSFr.: classification SMASS   An asteroid taxonomy built on the → Tholen classification but based on the presence or absence of → absorption features in the visible part of the spectrum. In many cases the two classifications are the same, but the Tholen C and S classes are subdivided in the SMASS classification.SMASS stands for the Small Main-belt Asteroid Spectroscopic Survey, → small; → main belt; → asteroid; → spectroscopic; → survey; → classification. Sobolev approximation   نزدینش ِ سوبولف   nazdineš-e SobolevFr.: approximation de Sobolev   A method allowing for a simplified solution to the → radiative transfer equation at frequencies of spectral lines in media moving with a high velocity gradient. This method assumes that the macroscopic velocity gradients are more important than local random variations of thermal line width: dv/dr > vth/l, where dv/dr is the velocity gradient, vth is the thermal broadening of the line, and l the length scale. The Sobolev approximation is only valid if the conditions of the gas do not change over the → Sobolev length. Under the Sobolev approximation, each point in the medium is isolated from other points, and the → radiative transfer problem becomes a local one and therefore much easier to solve.Named after the Russian astronomer Viktor Viktorovich Sobolev, Moving Envelopes of Stars [in Russian], Leningr. Gos. Univ., Leningrad (1947) [translated by S. Gaposchkin, Harvard Univ. Press, Cambridge, Mass. (1960)]; → approximation. socialization   هزانش   hazânešFr.: socialisation   A continuing process whereby an individual acquires a personal identity and learns the norms, values, behavior, and social skills appropriate to his or her social position (Dictionary.com).→ socialize; → -tion. Socratic irony   گواژه‌ی ِ سقراطی، ~ سقراتی   govâže-ye SoqrâtiFr.: ironie socratique   A means by which the pretended ignorance of a skillful questioner leads the person answering to expose his own ignorance (Collins).→ Socratic; → irony.