An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13116 Search : far
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 elliptical galaxy
  کهکشان ِ همپک ِ بیضیوار   
kahkešân-e hampak-e beyzivâr

Fr.: 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 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.

companion
  همدم   
hamdam (#)

Fr.: compagnon   

The fainter of the two components in a → binary system.

Companion from O.Fr. compaignon "fellow, mate," from L.L. companionem, lit. "bread fellow, messmate," from L. → com- "with" + panis "bread."

Hamdam "bearthing together, i.e. an intimate companion, friend," from ham- "with", → com- + dam "breath," Mod.Pers./Mid.Pers. damidan "to breathe, blow," Av. dāδmainya- "blowing up," cp. Skt. dham- "to blow," dhamati "he bows," Proto-Indo-Iranian *dhamH-, Proto-Iranian *damH- "to blow, breathe; to swell," PIE *dhemH- "to blow."

companion of Sirius
  همدم ِ تیشتر   
hamdam-e Tištar

Fr.: compagnon de Sirius   

A faint star of 8th magnitude in a binary system with → Sirius. Called also Sirius B, it is a → white dwarf with a mass comparable to that of the Sun, but with a diameter smaller than that of the Earth. The mean distance between the stars is about 20 A.U. (angular separation 4.6 seconds of arc), and their period of revolution about 50 years. This star was discovered in 1844 by Friedrich Bessel, who noticed that Sirius had a slight wobbling motion, as if it was orbiting an unseen object. In 1863, the optician and telescope maker Alvan Clark spotted the companion. The star was later determined to be a → white dwarf.

companion; → Sirius.

comparative
  همسنجشی   
hamsanješi (#)

Fr.: comparatif   

1) Of or relating to comparison.
2) Proceeding by, founded on, or using comparison as a method of study.
3) Grammar: Being, noting, or pertaining to the intermediate degree of the comparison of adjectives, as better and more beautiful, the comparative forms of good and beautiful, and of adverbs, as nearer and more carefully, the comparative forms of near and carefully (Dictionary.com).

comparison; → -ive.

comparator
  هم‌سنجگر   
hamsanjgar

Fr.: comparateur   

A device that compares the measured property of an object (position, shape, color, brightness) with a standard. → blink comparator.

L.L. comparator "comparer," from compara, → compare, + -tor suffix forming personal agent nouns, cf. Gk. -tor, Skt. -tar.

Hamsanjgar, agent noun from hamsanjidancomparison.

compare
  هم‌سنجیدن   
hamsanjidan (#)

Fr.: comparer   

To examine in order to note similarities and differences.

From O.Fr. comparer, from L. comparare "to match, make equal with, liken," from → com- "with" + parare "to make or esteem equal," from par "equal."

Sanjidan "to compare; to measure," from Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-. Other terms from this base in Pers.: lanjidan "to pull up," hanjidan, âhanjidan "to draw out," farhang "education, culture."

comparison
  هم‌سنجش   
hamsanješ (#)

Fr.: comparaison   

The act of comparing or the process of being compared.

From O.Fr. comparaison from L. comparationem, from p.p. stem of comparare, → compare.

Hamsanješ, from hamsanj present tense stem of hamsanjidan, → compare, + verbal noun suffix.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc coh col col col Com com com com com com com com Com con con con con con con con con con con con con coo Cor Cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>