birth binary population (BBP)
porineš-e dorinhâ hengâm-e zâdmân
Fr.: population binaire à la naissance
In star formation models, the population of binary components formed via random pairing of stars distributed according to the → canonical IMF.
Fr.: population complexe
Same as → composite population.
Fr.: population composite
A stellar population consisting of more than one → simple population. Also called complex population.
porineš-e gerdé, ~ disk
Fr.: population disque
Of a spiral galaxy, those stars that lie in a flattened disk and move in nearly circular orbits around its centre. They are Population I stars of all ages up to the age of the disk, but in general are younger than stars in → halo population.
→ disk; population, from L.L. populationem "a people, multitude," from populatio, from populare "to inhabit," from populus "people," related to plebes "the common people," cf. Gk. plethos "people, multitude, great number," from PIE base *pel- "to be full;" Mod.Pers. por "full," O.Pers. paru- "much, many," Av. pouru- "much, many," pərəna- "full," par- "to fill," Skt. puru-, Gk. polus, O.E. full "completely, full," from P.Gmc. *fullaz, O.H.G. fol, Ger. voll, Goth. full.
Like Gk., Pers. uses the concepts of "multitude, many, full" to denote "people, group, herd, flock". The following examples are all terms derived from O.Pers. paru- "much, many," Av. par- "to fill," pouru- "much, many," pərəna- "full" (Mod.Pers. por "full"): literary Pers. bâré "herd, flock," parré "a rank or file of soldiers, a circular disposition of troops," Lori, Qâyeni bor "group, tribe, herd," Torbat-Heydariyeyi, Qomi borr "heap, bundle, group," Qomi borreh "group, assemblage of people," Pashtu parrak "flock, herd," Urdu para "flock, herd," Lârestâni baila "group, tribe," Tabari balik "herd, flock." With this introduction, porineš "population," verbal noun of porinidan "to populate," infinitive of porin "populous," from por "mutitude, many, full" + -in attribution suffix.
Fr.: population finie
A → statistical population consisting of individuals or items which are finite in number.
Fr.: population du halo
Fr.: population infinie
A → statistical population consisting of individuals or items which either possesses the infinite property through some limiting process or is non-enumerable. For example, the population of all → real numbers between 0 and 1 and the population of all → integers are examples of infinite population. In case of random sampling with replacement, any population is always infinite.
porineš-e vâgardânidé, ~ vârun
Fr.: population inversée
In atomic physics, a condition in which there are more electrons in an upper energy level than in a lower one, while under normal conditions of thermal equilibrium the reverse is true. → optical pumping.
old stellar population
porineš-e setâre-yi-ye kohan
Fr.: population stellaire vielle
A population of stars in a stellar system that have definitely left the → main sequence.
Verbal noun of populate, from M.L. populatus, p.p. of populare "to inhabit," from L. populus "people."
In the IE languages the concepts of "full, many, multitude" and "people, group, herd, flock" are related. In Pers. several variants of por "full, much, many" denote "group, population," as in Lori, Qâyeni bor "group, tribe, herd," Torbat-Heydariyeyi, Qomi borr "heap, bundle, group," Qomi borreh "group, assemblage of people," Pashtu parrak "flock, herd," Urdu para "flock, herd," Lârestâni baila "group, tribe," Tabari balik "herd, flock;" other examples from literary Pers. bâré "herd, flock," parré "a rank or file of soldiers, a circular disposition of troops." Therefore, porineš "population," verbal noun of porinidan "to populate," infinitive of porin "populous," from por "mutitude, many, full" + -in attribution suffix. Por, from Mid.Pers. purr "full;" O.Pers. paru- "much, many;" Av. par- "to fill," parav-, pauru-, pouru- "full, much, many;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.
Population I star
setâre-ye-e porineš-e I
Fr.: étoiles de population I
A member of a class of relatively young stars, containing a large fraction of → metals, found mainly in the disk of the Galaxy.
Population II star
setâre-ye porineš-e II
Fr.: étoiles de population II
Population III star
setâre-ye porineš-e III
Fr.: étoile de population III
A member of the first generation of stars, formed out of pristine gas, enriched by → primordial nucleosynthesis alone. The material from which these stars formed consisted mostly of hydrogen and helium. Because neutral hydrogen clouds were free of dust, their cooling mechanism was drastically ineffective. As a result, these star forming clouds had a much higher temperature than in the present epoch, and their → Jeans mass was much higher. Therefore, these first generation of stars were principally massive, with a typical mass scale of order of about 100 Msun. Population III stars started forming about 300 million years after the → Big Bang at → redshifts between 50 and 6, when the Universe had between 1 and 5% of its present age. These stars were probably responsible for the → reionization of the Universe. Given their high mass, they lived only a few million years ending with either a → pair-instability supernova phase or a direct collapse to a → black hole. Population III stars thus initiated the chemical enrichment of the Universe and opened the way to more normal modes of star formation, namely → Population II. Some models predict a bimodal → initial mass function for the first stars, allowing also for solar mass stars. See also → extremely metal-poor star.
vâgardâni-ye porineš, vâruneš-e ~
Fr.: inversion des populations
In physics, specifically statistical mechanics, the state of an atomic or molecular system in which the number of members in an excited state is larger than those in lower energy states. → optical pumping; → inverted population.
Fr.: population simple
A set of stars resulting from a spatially (≤ few pc) and temporally (≤ Myr) correlated star formation event.
Fr.: population statistique
Fr.: population stellaire
stellar population synthesis
handâyeš-e porinešhâ-ye setâre-yi
Fr.: synthèse de poupulations stellaires
A theoretical model that reconstructs the integrated spectrum of → stellar populations from an empirical library of stellar spectra containing the range of types expected to be present in the sample. The light received from a given galaxy is emitted by a large number of stars that may have different masses, ages, and metallicities. Stellar population synthesis models are tools for interpreting the integrated light that we observe from the galaxies.