star formation region
nâhiye-ye diseš-e setâré
Fr.: région de formation d'étoiles
star formation time scale
marpel-e zamâni-ye diseš-e setâre
Fr.: échelle de temps de formation d'étoiles
The time necessary for a star to form. It depends inversely on the stellar mass.
Fr.: étoile S2
A → main sequence→ B-type star that orbits the → supermassive black hole candidate → Sgr A* in the → Galactic center. The star S2, which is bright enough for making detailed measurements, has a highly elliptical, 16-year-period orbit around Sgr A*. Near → pericenter at 120 → astronomical units, ~ 1400 → Schwarzschild radii, the star has an orbital speed of ~ 7650 km s-1, such that the first-order effects of → special relativity and → general relativity have become detectable with current capabilities (Auber et al., 2018, A&A 615, L15).
Fr.: système stellaire
Same as → stellar system.
Fr.: traînées stellaires
kahkešân-e disnade-ye setâré
Fr.: galaxie de formation d'étoiles
nâhiye-ye diseš-e setâré
Fr.: région de formation d'étoiles
A region in which → star formation is going on.
setâre-belk, belk-e setâré
Fr.: flambée d'étoiles
Simultaneous formation of a large number of stars in a region of a galaxy at an exceptionally high rate, compared to the usual star formation rates seen in most galaxies.
Fr.: galaxie à flambée d'étoiles
A galaxy showing a short-lived intense period of star formation that is unsustainable over the → Hubble time due to the limited supply of gas within a galaxy. Starburst galaxies were first classified by Searle & Sargent (1972) and Searle et al. (1973), based on the blue colors produced by the → massive stars formed during the burst. In the local Universe, starbursts create approximately 10% of the radiant energy and 20% of the massive stars. At z = 1, starburst characteristics are found in 15% of galaxies, presumably attributable to the greater amounts of gas typically present in young galaxies and increased galactic interactions. The starburst's impact on a galaxy and the surrounding → intergalactic medium is primarily due to the consumption of gas that fuels the burst and the feedback from massive stars formed in the burst (McQuinn et al. 2010, astro-ph/1008.1589).
Fr.: effet Stark
Named after Johannes Stark (1874-1957), a German physicist, and Physics Nobel Prize laureate (1919); → effect.
Fr.: tremblement d'étoile
An astrophysical phenomenon that occurs when the → crust of a → neutron star undergoes a sudden adjustment, analogous to an → earthquake on Earth. Starquakes are thought to be caused by huge → stresses exerted on the surface of the neutron star produced by twists in the ultra-strong interior → magnetic fields. They are thought to be the source of the intense → gamma-ray bursts that come from → soft gamma repeaters.
Fr.: tache stellaire
A phenomenon similar to a → sunspot but occurring on the surface of a star other than Sun. Due to spatial resolution constraints, starspots so far observed are in general much larger than those on the Sun, up to about 30% of the stellar surface may be covered, corresponding to sizes 100 times greater than those on the Sun.
stimulated star formation
diseš-e gavâlide-ye setâré
Fr.: formation stimulée d'étoiles
A process in which a star is not formed spontaneously but is provoked by the action of external forces, such as pressure and shock on a molecular cloud by close-by → massive stars, → supernova explosions, etc. See also → sequential star formation.
stochastic self-propagating star formation
diseš-e setâregân bâ xod-tuceš-e kâturgin
Fr.: formation d'étoiles par auto-propagation stochastique
A mechanism that could be responsible for global → spiral structure in galaxies either by itself or in conjunction with spiral → density waves. In this mechanism, star formation is caused by → supernova-induced → shocks which compress the → interstellar medium. The → massive stars thus formed may, when they explode, induce further → star formation. If conditions are right, the process becomes self-propagating, resulting in agglomerations of young stars and hot gas which are stretched into spiral shaped features by → differential rotation. Merging of small agglomerations into larger ones may then produce large-scale spiral structure over the entire galaxy. The SSPSF model, first suggested by Mueller & Arnett (1976) was developed by Gerola & Seiden (1978). While the → density wave theory postulates that spiral structure is due to a global property of the galaxy, the SSPSF model examines the alternative viewpoint, namely that spiral structure may be induced by more local processes. The two mechanisms are not necessarily mutually exclusive, but they involve very different approaches to the modeling of galaxy evolution. The SSPSF gives a better fit than the density wave theory to the patchy spiral arms found in many spiral galaxies. However, it cannot explain → galactic bars.
Fr.: étoile sous-lumineuse
A star that is less luminous than a main-sequence star of the same spectral type.
super star cluster (SSC)
Fr.: super amas stellaire
A group of hundreds to thousands of very young stars packed into an unbelievably small volume of a few parsecs in size. These objects represent the youngest stage of → massive star cluster evolution yet observed. The most massive and dense SSCs, with ages less than 106 years, may be proto globular clusters. SSCs are thought to dissolve within 10 million years and merge into the field star population.
Fr.: étoile super-canonique
Fr.: étoile très riche en métaux
supergiant B[e] star (sgB[e])
setâre-ye B[e]-ye abarqul
Fr.: étoile B[e] supergéante
A highly luminous → B[e] star with a luminosity greater than 104L_sun. A number of such objects exist in the → Magellanic Clouds, e.g. LMC R126, R66, SMC R4, and R50. A likely example in our Galaxy is MWC 300.
supermassive neutron star
setâre-ye notroni-ye abar-porjerm
Fr.: étoile à neutron supermassive