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The hypothesis first put forward by Immanuel Kant (1724-1804) according to which the objects termed "spiral nebulae" were stellar systems comparable to our own → Milky Way galaxy. At the end of the 18th century, William Herschel (1738-1822) using his giant reflectors discovered thousands of such nebulae. However, in spite of advances in observations it was never possible to prove Kant's idea until the second decade of the twentieth century. The observations using the Mount Wilson 2.50m (100 inch) telescope allowed Edwin Hubble in 1924 to firmly establish that the "spiral nebulae" were unquestionably extragalactic.
izo- (#), ham- (#)
Prefix denoting "equal; homogeneous; uniform." Also is- sometimes before a vowel.
From L.L., from Gk. isos "equal."
Izo-, loan from Gk. isos, as above. The Pers. ham-→ com- is overused; therefore this dictionary adopts izo-.
izobâr (#), izofešâr
1) Meteo.: A line connecting points having equal pressure.
From Gk. isobares "of equal weight," from → iso- + bar, from baros "weight," cognate with Pers. bâr "charge, weight" (Mid.Pers. bâr, from O.Pers./Av. bar- "to bear, carry," Mod.Pers. bordan "to carry;" L. brutus "heavy, dull, stupid, brutish;" Skt. bhara- "burden, load," bharati "he carries;" Mod.Pers. gerân "heavy;" Skt. guru; L. gravis; PIE *gwere- "heavy;" *bher- "to carry, give birth").
Fr.: processus isobare
A process taking place at constant pressure. → polytropic process.
Fr.: spin isobarique
Same as → isospin.
Fr.: processus isochore
A process in which the volume remains unchanged.
Farâravand, → process; izogonj, from izo→ iso- + gonj "volume," gonjdan "to be contained; to hold exactly; to be filled;" Mid.Pers. winj- "to be contained;" Proto-Iranian *uiac-/*uic-; cf. Skt. vyac- "to contain, encompass," vyás- "extent, content, extension;" L. uincire "to bind."
A curve on a → Hertzsprung-Russell diagram connecting all stars having the same age.
Isochrone, back formation from isochronal, from Gk. → iso- + khronos "time."
Having similar angles.
Fr.: trajectoire isogonale
Math.: A curve which intersects every member of a given one-parameter family of curves at one and the same angle.
Line joining geographical points of equal insolation during a specific interval of time.
Fr.: angle isocinétique
To set or place apart; detach or separate so as to be alone.
Isolate, back-formation from isolated, from Fr. isolé "isolated," from It. isolato, from L. insulatus "made into an island," from insula "island;" maybe from *en-salos "in the sea," from salum "sea."
Vâyutidan, from vâ- denoting "separation" (also "reversal, opposition; repetition; back, backward," variant of bâz-, from Mid.Pers. abâz-, apâc-; O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind") + Mid.Pers. yut "separate, different," Mod.Pers. jodâ "separate, apart;" Av. yuta- "separate, apart" + -idan infinitive suffix.
Set apart or separated from others or other things.
Past participle of → isolate.
Fr.: galaxie isolée
A galaxy that is not a member of a dense aggregate. In other words, a galaxy that is formed in a low galactic density environment and has evolved without major interactions with other galaxies of similar mass.
isolated massive star formation
diseš-e vâyutide-ye setâre-ye porjerm
Fr.: formation isolée d'étoile massive
Massive star formation outside → OB associations. Recent observational findings suggest that → massive star formation is a collective process. In other words, massive stars form in → cluster environments and the mass of the most massive star in a cluster is correlated with the mass of the cluster itself. Nevertheless, other observational results give grounds for supposing that massive stars do not necessarily form in clusters but that they can be formed as isolated stars or in very small groups. According to statistical studies nearly 95% of Galactic → O star population is located in clusters or OB associations. This means that a small percentage, about 5%, of high mass stars may form in isolation. Isolation is meant not traceable to an origin in an OB association. This definition therefore excludes → runaway massive stars, which are thought to result from either dynamical interaction in massive dense clusters, or via a kick from a → supernova explosion in a → binary system. Alternatively, isolated massive star has been defined as follows: An O-type star belonging to a cluster whose total mass is < 100 Msun and moreover is devoid of → B stars (Selier et al. 2011, A&A 529, A40 and references therein).
isolated neutron star (INS)
setâre-ye notroni-ye vâyutidé
Fr.: étoile à neutron isolée
A → neutron star which does not belong to a → binary system, does not have radio emission, and is not surrounded by a progenitor → supernova remnant. INSs appear to be thermally cooling with no emission outside the → soft X-ray band, except for faint optical/UV counterparts. Although these properties are similar to those of → compact central object (CCO)s, they are a distinct class because they lack any observable associated supernova remnant or nebula. There are presently seven confirmed INSs (sometimes referred to as The Magnificent Seven), six of which have measured weakly modulated X-ray pulsations with periods between 3 s and 11 s, much longer than those of CCOs (A. K. Harding, 2013, Front. Phys. 8, 679).
Fr.: système isolé
An act or instance of isolating; the state of being isolated.
Verbal noun of → isolate.
Physics: Any of two or more nuclei having the same atomic number A and mass number Z
but different half-lives.
Back formation from isomeric, from → iso- + mer a combining form meaning "part," from Gk. meros "part, portion, share."
Izomer, loan from Fr. isomère.