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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 commutation rules   رزن‌های ِ آموتش   razanhâ-ye âmutešFr.: règles de commutation   The specification of commutators of operators that in quantum physics correspond to the coordinates and momenta of a system.→ commutation; → rule. commutative   آموتنده   âmutandéFr.: commutatif   (adj.) Of or pertaining to → commutation.Adj. from → commute. commutative law   قانون ِ آموتشی   qânun-e âmutešiFr.: loi commutative   A principle holding for the operations of addition and multiplication (in some number domains) that asserts that the consequence of the given operation is not affected by the order in which the terms are considered. Thus x + y = y + x; x . y = y . x.→ commutative; → law. The first use of the word commutative in this sense is ascribed to the French mathematician François Joseph Servois (1768-1847). commutativity   آموتندگی   âmutandegiFr.: commutativité   The state or quality of being commutative.Noun from → commutative. commutator   آموتگر   âmutgarFr.: commutateur   Math.: The commutator of a and b is the element c of a group such that bac = ab.Agent noun from → commute. commute   آموتیدن   âmutidanFr.: échanger   To substitute (one thing for another); exchange. → mutation. Math., logic: To satisfy or engage in a commutative operation.From L. commutare "to change altogether," from → com- + mutare "to change," from PIE base *mei- "to change, go, move;" cf. Av. miθô "inverted, false," miθaoxta- "wrong spoken;" Skt. methati "changes, alternates, joins, meets," mithah "mutual, reciprocal;" L. meare "to go, pass," mutuus "done in exchange;" Goth. maidjan "to change;" E. prefix mis- (in mistake).Âmutidan, from intensive prefix â- + mut, from L. mutare cognate with Av. miθô, as above, + -idan infinitive suffix. comoving   هم‌جنب، هم‌میاو   hamjonb, ham-miyâvFr.: comobile   Moving together or in a correlated way.From → com- "together," + pr.p. of → move.Hamjonb, ham-miyâv "comoving," from ham- "together," → com-, + jonb or miyav "moving, mover," present stems of jondidan and miyâvidan "→ move." comoving coordinates   هماراهای ِ هم‌جنب   hamârâhâ-ye hamjonbFr.: coordonnées comobiles   A system of coordinates used in cosmology which is fixed with respect to the overall → Hubble flow of the universe. A given galaxy's location in comoving coordinates does not change as the Universe expands.→ comoving; → frame. comoving distance   اپست ِ هم‌میاو   apest-e ham-miyâvFr.: distance comobile   1) A distance in → comoving coordinates between two points in space at a given cosmological time. In other words, the distance between two nearby objects in the Universe which remains constant with epoch if the two objects are moving with the → Hubble flow. More specifically, it is the → proper distance divided by the ratio of the → scale factor of the Universe between then, a(t)em, and now, a(t)obs: DC = Dproper . [a(t)obs/a(t)em]. In terms of → redshift (z), it is the proper distance multiplied by (1 + z). At the present epoch, i.e. a = a(tobs) = 1, DC = Dproper. If the objects have no peculiar velocity their comoving distance at any time is the same as their distance today. The comoving distance of the → cosmic horizon is about 48 × 109→ light-years. 2) Transverse comoving distance: In a non-flat Universe, the comoving distance between two events at the same → redshift but separated on the sky by some angle. It is expressed by trigonometric functions of → curvature, → comoving distance, and the → Hubble distance accounting for the curvature of space. In a flat universe (Ωk) it is the same as the → comoving distance. 3) Line-of-sight comoving distance: The total line-of-sight comoving distance from us to a distant object computed by integrating the infinitesimal comoving distance contributions between nearby events along the radial ray from the time temit, when the light from the object was emitted, to the time tobs, when the object is observed.→ comoving; → distance. comoving frame   چارچوب ِ هم‌جنب   cârcub-e hamjonbFr.: rérérentiel comobile   A → reference frame that is attached to a moving object. The object in this frame is therefore at rest.→ comoving; → frame. comoving volume   گنج ِ هم‌جنب   gonj-e hamjonbFr.: volume comobile   The volume that a structure at → redshift  z would have if it was seen at the → current cosmological epoch (defined by z = 0).→ comoving; → volume. compact   ۱) همپک؛ ۲) همپکیدن، همپک کردن   1) hampak; 2) hampakidan, hampak kardanFr.: 1) compacte; 2) condenser, resserer   1) Closely and firmly joined or packed together; Occupying little space compared with others of its type. 2) To reduce in size or volume.M.E., from L. compactus "concentrated," p.p. of compingere "to fasten together," from → com- "with, together" + pangere "to fix, fasten," cf. Gk. pegnunai "to fasten, coagulate;" PIE *pag-/*pak- "to fasten."1) Hampak, from ham-, → com-, + pak, from pakidé [Mo'in, Dehxodâ] "thick, dense, compact," in Hamadâni pukida "much, full, abundant," Kordi pêk "together, joint," pêk hatin "to be made up of," pêk hênan "to collect, constitute," from PIE *pag-/*pak- as above? 2) Hampakidan, from hampak + -idan infinitive suffix; hampak kardan, from hampak + kardan "to do, make, perform," → -ize. compact binary star system   راژمان ِ درین ِ همپک   râžmân-e dorin-e hampakFr.: système binaire compact   A binary star system which is composed of a collapsed object (→ degenerate dwarf, → neutron star, or → black hole) in orbit with a low-mass (≤ 0.5 Msol) secondary star, wherein the collapsed star → accretes matter from its → companion. These two objects form a binary system of overall dimensions 106 km with an orbital period of only hours or less. See also: → X-ray binary. → compact; → binary; → star; → system. compact central object (CCO)   بر‌آخت ِ همپک ِ مرکزی   barâxt-e hampak-e markaziFr.: objet compact central   An → X-ray source detected close to the center of young → supernova remnant (SNR)s that has no apparent emission in other wave-bands and no binary companions. Although these sources have been known and studied for several decades without much understanding of their nature, exciting results over the past few years have brought them into the forefront of → neutron star studies. They have soft, exclusively thermal spectra in the few hundred eV range and X-ray luminosities around 1033 - 1034 erg s-1. About ten CCOs are presently known, including the central sources of CasA, Puppis A and Kes 79 supernova remnants. Several, J1852+0040 in Kes79, J0822.0-4300 in Puppis A and 1E 1207.4-5209 in PKS 1209-51/52, have detected pulsations in the hundreds of milliseconds range. J1852+0040 has a detected → period derivative, indicating that it is spinning down like a → rotation-powered pulsar (RPP). The measured period and either measurements or constraints on period derivative indicate that these sources have very low → magnetic fields in the range 1010 - 1011 G assuming magnetic dipole braking. Since their SNRs are all young, ~ 103 - 104 yr, they were probably born with unusually low magnetic fields, which makes them "anti-magnetars" (A. K. Harding, 2013, Front. Phys. 8, 679 and references therein).→ compact; → central; → object. compact elliptical galaxy   کهکشان ِ همپک ِ بیضیوار   kahkešân-e hampak-e beyzivârFr.: galaxie elliptique compacte   A galaxy belonging to a comparatively rare class of galaxies possessing very small radii and high central → surface brightnesses. The prototype is the → Local Group  → dwarf galaxy M32. At the low mass end of the → early-type galaxy population, the well-known → mass-size relation splits into diffuse and compact branches. The compact branch is composed of compact elliptical galaxies (cEs) and may even extend to the regime of → ultracompact dwarfs. Compact ellipticals have → effective radii (Re) generally less than 0.6 kpc, while their diffuse counterparts, the → dwarf elliptical galaxies (dEs) or → dwarf spheroidals (dSphs), have Re ~ 0.6-3 kpc at similar mass. One formation scenario for cEs proposes that they are low-mass classical → elliptical galaxies, in accordance with the fact that they follow the same trend on the fundamental plane as the giant ellipticals. This implies formation through hierarchical mergers, as in "normal" ellipticals. Most cEs are notably more → metal-rich than dEs and are outliers from the → mass-metallicity relation of massive early type galaxies and low-mass galaxies in the Local Group. An alternative formation scenario addresses the problem of high metallicity by proposing that cEs are the remnants of larger, more massive galaxies. In this scenario, their disks are stripped by strong tidal interactions (→ tidal stripping) with an even more massive host galaxy, leaving only the compact, metal-rich bulges (Du et al., 2018, arxiv/1811.06778 and references therein).→ compact; → elliptical; → galaxy. compact galaxy   کهکشان ِ همپک   kahkašân-e hampakFr.: galaxie compacte   A galaxy with no disk or nebulous background and a high surface brightness that appears only barely larger than a star-like point on a sky survey photograph.→ compact; → galaxy. compact H II region   ناحیه‌ی ِ H IIی ِ همپک   nâhiye-ye H II-ye hampakFr.: région H II compacte   A Galactic H II region with an electron density ≥ 103 cm-3 and of a linear dimension ≤ 1 pc.→ compact; → H II region. compact high-velocity clouds (CHVCs)   ابرهای ِ همپک ِ تندرو   abrhâ-ye hampak-e tondrowFr.: nuages compacts à grande vitesse   A population of relatively small (typically < 2°) → high-velocity clouds, which are spatially and kinematically isolated from the gas distribution in their environment. They are thought to be located in the → intergalactic medium of the → Local Group. compact massive galaxy (CMG)   کهکشان ِ پرجرم ِ همپک   kahkešân-e porjerm-e hampakFr.: galaxie massive compacte   A galaxy with a stellar mass of M ≥ 1011Msun and an → effective radius of Re ≤ 1.5 kpc. Many studies have shown that massive galaxies with low → star formation rates were remarkably compact at a → redshift of z≥ 2. At fixed stellar mass of Mstars ≅ 1011Msun, quiescent galaxies are a factor of ~ 4 smaller at z = 2 than at z = 0. As the stellar mass of the galaxies also evolves, the inferred size growth of individual galaxies is even larger. It is unlikely that all massive galaxies in the present-day Universe had a compact progenitor. However, the vast majority of CMGs that are observed at z = 2 ended up in the center of a much larger galaxy today. Their size growth after z = 2 is probably dominated by minor → mergers. Such mergers are expected because other mechanisms cannot easily produce the observed scaling between size growth and mass growth (P. G. van Dokkum1 et al., 2015, ApJ 813, 23).→ compact; → massive; → galaxy. compact object   بر‌آخت ِ همپک   barâxt-e hampakFr.: objet compact   An astronomical object that is substantially denser or more compact than most objects of its class. More specifically, a → neutron star or a → stellar black hole.→ compact; → object.