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: 261 Search : star
Stark effect
  اُسکر ِ اشتارک   
oskar-e Stark

Fr.: effet Stark   

The → splitting of spectral lines of atoms and molecules due to the presence of an external electric field, which slightly changes the → energy levels of the atom. → Zeeman effect.

Named after Johannes Stark (1874-1957), a German physicist, and Physics Nobel Prize laureate (1919); → effect.

starquake
  ستاره-لرز   
setâre-larz

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.

star; → quake.

starspot
  ستاره-لک   
setâre-lak

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.

star; → spot.

stimulated star formation
  دیسش ِ گوالیده‌ی ِ ستاره   
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.

Stimulated, p.p. of → stimulate; → star formation.

stochastic self-propagating star formation
  دیسش ِ ستارگان با خود-توچش ِ کاتورگین   
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.

stochastic; → self; → propagate; → star; → formation.

subluminous star
  ستاره‌ی ِ زیر-تابان   
setâre-ye zir-tâbân

Fr.: étoile sous-lumineuse   

A star that is less luminous than a main-sequence star of the same spectral type.

sub-; → luminous; → star.

super star cluster
  اَبَر خوشه‌ی ِ ستاره‌ای   
abar-xuše-ye setâre-yi

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.

super; → star; → cluster.

super-canonical star
  ستاره‌ی ِ ابر-هنجاروار   
setâre-ye abar-hanjârvâr

Fr.: étoile super-canonique   

A star whose mass exceeds the → canonical upper limit of the stellar → initial mass function (Kroupa et al. 2012, arXiv:1112.3340).

super-; → canonical; → star.

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.

supergiant; → B[e] star.

supermassive neutron star
  ستاره‌ی ِ نوترونی ِ ِ اَبَر-پرجرم   
setâre-ye notroni-ye abar-porjerm

Fr.: étoile à neutron supermassive   

A → neutron star of mass above the typical value that is temporarily prevented from → collapseing into a → black hole because of its rapid → rotation.

supermassive; → neutron; → star.

supermassive star
  ستاره‌ی ِ اَبَر-پرجرم   
setâre-ye abar-porerm

Fr.: étoile supermassive   

A star with an initial mass over about 120 solar masses. The existence of such stars is the present Universe is not confirmed. Such stars were proposed as an explanation for very bright O type stars in the Large Magellanic Cloud, but these are now known to be clusters of ordinary O stars. → very massive star; → massive star.

supermassive; → star.

supra-horizontal branch star
  ستاره‌ی ِ فراز ِ شاخه‌ی ِ افقی   
setâre-ye farâz-e šâxe-ye ofoqi

Fr.: étoile au-dessus de la branche horizontale   

A member of a rare class of objects found in → globular clusters to lie about one magnitude above and to the blue part of the → horizontal branch. These stars are identified as post → EHB stars on their way from to the → asymptotic giant branch.

supra-; → horizontal; → branch; → star.

symbiotic B[e] star (symB[e])
     
setâre-ye B[e]-ye hamzi

Fr.: étoile B[e] symbiotique   

A → B[e] star whose spectrum shows the presence of a cool component characterized mainly by → TiO bands.

symbiotic; → B[e] star.

symbiotic star
  ستاره‌ی ِ همزی   
setâre-ye hamzi

Fr.: étoile symbiotique   

A stellar object whose optical spectrum displays lines characteristic of gases of two very different temperatures, typically of an M star (3500 K) and a B star (20 000 K) superimposed. A symbiotic star is in fact a close binary system.

symbiotic; → star.

T Tauri star
  ستاره‌ی ِ T-گاو   
setâre-ye T-Gâv

Fr.: étoile T Tauri   

A member of a class of young stellar objects of roughly 1 solar mass showing strong → infrared excess emission attributed to → circumstellar disks and found within or close to molecular clouds. T Tauri stars are → protostars in the final stages of formation to become a stable → main sequence star. The nuclear reactions in their core have not yet stabilised and the stars are known for the variability of their brightness. See also → classical T Tauri star, → weak-line T Tauri star.

T Tauri; → star.

tight star cluster
  خوشه‌ی ِ ستاره‌ای ِ تنگ   
xuše-ye setâreyi-ye tang

Fr.: amas stellaire serré   

A cluster of stars in which members are closely situated so that high resolution observations are required to distinguish them individually.

tight; → star cluster.

triggered star formation
  دیسش ِ ماشه‌ای ِ ستاره   
diseš-e mâše-yi-ye setâré

Fr.: formation d'étoiles déclanchée   

The formation of second-generation stars in a → molecular cloud, as set off by the action of → massive stars. → sequential star formation; → radiation-driven implosion.

trigger; → star formation.

triple star
  ستاره‌ی ِ سه‌تایی   
setâre-ye setâyi

Fr.: étoile triple   

A group of three stars visually or physically associated with each other. → triple system.

triple; → star

turnoff star
  ستاره‌ی ِ رهگشت   
setâre-ye rahgašt

Fr.: étoile du tournant final de la séquence principale   

A star that has ended → hydrogen burning in its core but is still burning hydrogen in a shell that surrounds the core, just before evolving into a → red giant.

turnoff; → star.

Tycho's star
  ستاره‌ی ِ توگو   
setâre-ye Tycho

Fr.: étoile de Tycho   

A → supernova of Type Ia in the constellation → Cassiopeia, which Tycho Brahe observed in November 1572. At its peak it was as bright as Venus and was visible in the daytime, reaching a magnitude of about -4. It is now visible as a → supernova remnant about 20 light-years across at a distance of about 7,500 light-years. It is associated with faint emission in the optical and X-rays, but is a strong radio source. Other designations: SN 1572, 3C 10, B Cas, 2U 0022+63.

Named after the Danish astronomer Tycho Brahe (1546-1601), who described the event; → star.

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