An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < abs act att clu com dif fac Gal gal imp int pac rad ref sub wei > >>

Number of Results: 304 Search : act
clumping factor
  کروند ِ گوده‌داری   
karvand-e gudedâri

Fr.: facteur de grumelage   

The ratio fcl = <ρ2> / <ρ >2, where ρ represents the → stellar wind density and the brackets mean values. Unclumped wind has fcl = 1 and → clumping becomes significant for fcl≅ 4.

clumping; → factor.

cofactor
  همکروند   
hamkarvand

Fr.: cofacteur   

A number associated with an → element of a → determinant. If A is a square matrix [aij], the cofactor of the element aij is equal to (-1)i+j times the determinant of the matrix obtained by deleting the i-th row and j-th column of A.

co-; → factor.

cometary activity
  ژیرندگی ِ دنباله‌دار   
žirandegi-ye donbâledâr

Fr.: activité cométaire   

The appearance of → gas and → dust features from the rocky-icy nucleus of a comet when approaching the Sun (→ cometary atmosphere, → cometary tail). The → sublimation of → water can explain cometary activity at distances from the Sun up to about 4 → astronomical units. At larger distances, the average temperature of the → comet nucleus' surface is less than 140 K, too low for efficient sublimation of water → ice. However, there are many examples of cometary activity at larger distances. This can probably be due to the sublimation of more → volatile → chemical species. Indeed, radio spectroscopic observations of comets at large distances have revealed an important → outgassing of → carbon monoxide (CO), which can sublimate at temperatures as low as 25 K.

cometary; → activity.

common fraction
  برخه‌ی ِ همدار   
barxe-ye hamdâr

Fr.: fraction d'entiers   

A fraction written as a/b where a and b are → positive  → integers, as opposed to a → decimal fraction; for example, 5/7. Common fractions are sometimes also called → vulgar fractions.

common; → fraction.

compact
  ۱) همپک؛ ۲) همپکیدن، همپک کردن   
1) hampak; 2) hampakidan, hampak kardan

Fr.: 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 hampak

Fr.: 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 markazi

Fr.: 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 galaxy
  کهکشان ِ همپک   
kahkašân-e hampak

Fr.: 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 hampak

Fr.: 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 tondrow

Fr.: 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; → high-velocity cloud.

compact massive galaxy (CMG)
  کهکشان ِ پرجرم ِ همپک   
kahkešân-e porjerm-e hampak

Fr.: 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 hampak

Fr.: 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.

compact planetary nebula B[e] star (cPNB[e])
  ستاره‌یِ B[e]ی ِ میغ ِ سیاره‌ای ِ همپک   
setâre-ye B[e]-ye miq-e sayyâre-yi-ye hampak

Fr.: étoile de nébuleuse planétaire compacte   

A star whose spectrum shows striking similarities to → B[e] stars and is evolving into a → planetary nebula (→ preplanetary nebula).

compact; → planetary; → nebula; → B[e] star.

compact radio source
  خن ِ رادیویی ِ همپک   
xan-e râdioyi-ye hampak

Fr.: source radio compacte   

An object emitting intense energy in radio wavelength from a small, unresolved central region.

compact; → radio source.

compact space
  فضای ِ همپک   
fazâ-ye hampak

Fr.: espace compact   

A topological space for which every collection of open sets that covers the space has a finite subset that also covers the space.

compact; → space.

compactification
  همپکانش   
hampakâneš

Fr.: compactification   

1) Math.: A process applied to topological spaces having many dimensions to make them compact spaces.
2) Physics: In string theory, the process of "curling up" the extra dimensions (six in the superstring theory). According to these theories, the Universe actually has 10 spatial dimensions but that 7 of them have become "compactified" down to subatomic size and thus are unobservable.

Compactification, n. from → compactify.

compactify
  همپکانیدن   
hampakânidan

Fr.: compactifier   

Verbal form of → compactification.

Compactify, from → compact + -ify "cause to become," M.E. -fien, from O.Fr. -fier, from L. -ficare, root of facere "to make, do;" PIE base *dhe- "to put, to do" (cf. Skt. dadhati "puts, places;" Av. dadaiti "he puts," O.Pers. ada "he made," Gk. tithenai "to put, set, place."

compaction
  همپکش   
hampakeš

Fr.: compactage   

1) The act of compacting or the state of being compacted.
2) Geology: The physical process whereby the volume of a fixed mass of sediment reduces either by the weight of overlying deposits or by the pressure of earth movements.

compact; → -tion.

compactness
  همپکی، همپکیدگی   
hampaki, hampakidegi

Fr.: compacité   

1) General: The quality of being compact.
2) For a → compact object, a rough measure of the importance of gravity, defined by a dimension-less quantity which is the ratio between its gravitational radius (→ Schwarzschild radius) and its physical radius. It is expressed as φ = 2 GM / c2 R, where M and R are the mass and radius of the object respectively, and G and c are the → gravitational constant and speed of light respectively. For a → black hole  φ is of order unity (by definition), for a → white dwarf it is of order 10-4, and for a → neutron star  φ is around 0.5.

compact + → -ness.

complex fraction
  برخه‌ی ِ همتافت   
barxe-ye hamtâft

Fr.: fraction complexe   

A fraction in which the → numerator or → denominator, or both, contain fractions. For example (3/5)/(6/7). Also called → compound fraction.

complex; → fraction.

<< < abs act att clu com dif fac Gal gal imp int pac rad ref sub wei > >>