Fr.: étoile de comparaison
A non-variable star used to monitor the variations of another nearby star.
cosmic star formation peak
cakâd-e keyhâni-ye diseš-e setâregân
Fr.: pic de formation stellaire cosmique
A crucial period in the history of the → Universe, when the bulk of stars in massive galaxies were likely formed. Observations of young stars in distant galaxies at different times in the past have indicated that the → star formation rate peaked at the → redshift of z ~ 2, some 10 billion years ago, before declining by a factor of around ten to its present value (P. Madau & Dickinson, 2014, arXiv:1403.0007).
Fr.: étoile noire, ~ sombre
A hypothetical stellar object whose structure or evolution has been affected by → dark matter. Dark matter models predict that in the → early Universe dark matter (in the form of → WIMPs) should congregate and annihilate in the cores of → Population III stars. The result would be dark stars with properties very different from ordinary stars. The reason is that the presence of large amounts of dark matter during the formation of a star inhibits the collapse and can partially prevent further cooling of the gas beyond a certain critical point, well before a → main sequence object has formed. As a consequence, dark matter stars should be more massive, more luminous, and live longer than Pop. III stars, but would be cooler. The formation of dark stars could have had an impact on the → reionization history of the Universe (see, e.g., P. Scott, 2011, astro-ph/1101.1029, and references therein).
setâre-ye gerdé, ~ disk
Fr.: étoile de disque
A star that lies within the → galactic disk of a → spiral galaxy. Stars belonging to the → thin disk, such as the Sun or Alpha Centauri, lie at a typical distance of about 1,000 → light-years from the galactic midplane. There are also → thick disk stars, such as Lalande 21185, that lie at an average distance of about 3,500 light-years from the midplane.
Fr.: étoile donneuse
In a → binary system, a star whose gas is → accreted by a compact companion. The donor may be a → giant or a → supergiant with an enormously distended atmosphere and a significant → stellar wind, or a star filling its → Roche lobe in a → close binary.
setâre-ye dotâyi (#)
Fr.: étoile double
An apparently single star which better observational resolution shows it to be a pair of closely lying stars. They may or may not be physically related.
setâre-ye kutulé (#)
Fr.: étoile naine
A star that burns its hydrogen content to produce its energy and therefore belongs to the main-sequence luminosity class.
early spectral class star
setâré bâ rade-ye binâbi-ye âqâzin
Fr.: étoile de type spectral précoce
setâre-ye gun-ye âqâzin (#)
Fr.: étoile de type précoce
Fr.: étoile EBH
Same as → extreme horizontal branch star.
Fr.: étoile électrofaible
A postulated type of star that could form toward the end of a → massive star's life, after → nuclear fusion has stopped in its → core, and before the star → collapses into a → black hole. In those → extreme conditions, when → temperature and → density inside the star are very high, → quarks could convert into → leptons. Hence huge amounts of energy can be released, much of which would be in the form of → neutrinos.
Fr.: étoile enfouie
A newborn star which is tightly enveloped by a surrounding cloud of gas and dust.
Ebedded p.p. of embed, from en- + bed from O.E. bed "bed," from P.Gmc. *badjam "sleeping place dug in the ground" (O.H.G. betti; Ger. bett); PIE base *bhedh- "to dig, pierce;" cf. Gk. bothyros "pit;" L. fodere "to dig," fossa "ditch;" → star.
Setâré, → star; forupušidé, p.p. of forupušidan, from foru- "below; beneath; down, downwards;" Mid.Pers. frôt "down, downwards;" O.Pers. fravata "forward, downward;" Skt. pravát- "a sloping path, the slope of a mountain" + pušidan "to cover, conceal, clothe; to wear clothes;" Mid.Pers. pôšidan, pôš- "to cover, put on, wear;" cf. Mid.Pers. pôst; Mod.Pers. pust "skin, hide;" O.Pers. pavastā- "thin clay envelope used to protect unbaked clay tablets;" Skt. pavásta- "cover;" Proto-Indo-Iranian *pauastā- "cloth."
setâre-ye šâmgâh (#)
Fr.: étoile du soir
Fr.: étoile évoluée
A star that has left the → main sequence.
Fr.: étoile excitatrice
Fr.: étoile exotique
A hypothetical → compact object composed of particles other than electrons, protons, and neutrons balanced against → gravitational collapse by → degeneracy pressure of corresponding quantum properties.
Fr.: étoiles d'extinction
Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.
extreme HB star
Fr.: étoile EBH
Same as → extreme horizontal branch star.
extreme horizontal branch star (EHB)
setâre-ye šâxe-ye ofoqi-ye ostom
Fr.: étoile de la branche horizontale extrême
The hottest variety of stars on the → horizontal branch with temperatures ranging from 20,000 to 40,000 K. EHB stars are distinguished from normal horizontal branch stars by having extremely thin, inert hydrogen envelopes surrounding the helium-burning core. They are hot, dense stars with masses in a narrow range near 0.5 Msun. These stars have undergone such extreme mass loss during their first ascent up the giant branch that only a very thin hydrogen envelope survives. Stars identified as EHB stars are found in low metallicity globular clusters as an extension of the normal HB.
extremely metal-poor star (EMPS)
stâre-ye ostomâné kamfelez
Fr.: étoile extrêmement faible en métaux
A star with an iron abundance [Fe/H] < -3 found in a → galactic halo. These stars, whose → metallicity is typically less than one thousandth of the solar value, are believed to have formed shortly after the → Big Bang, 13.7 billion years ago. The number of such stars depends on the primordial → initial mass function. If the IMF were steep, there could, in principle, be a lot of EMPSs formed at high → redshifts. Thus many of them could have ended up in the halos of galaxies. See also → Population III star.