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: 272 Search : Star
SHB star
  ستاره‌ی ِ SHB   
setâre-ye SHB

Fr.: étoile SHB   

Same as → supra-horizontal branch star.

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

shell star
  ستاره‌ی ِ پوسته‌دار   
setâre-ye pustedâr

Fr.: étoile à enveloppe   

A main-sequence star, usually of spectral class B to F, whose spectrum shows bright emission lines superimposed on the normal absorption lines. The emission spectrum is explained by the presence of a circumstellar shell of gas surrounding the star at the equator. Shell stars are fast rotators.

shell; → star.

shooting star
  شهاب   
šahâb (#)

Fr.: étoile filante   

Colloquial name for → meteor.

Shooting, from shoot (v.); M.E. shoten; O.E. sceotan "to shoot" (cf. O.N. skjota, Du. schieten, Ger. schießen), from PIE base *skeud- "to shoot, to chase, to throw;" → star.

Šahâb, → meteor.

Slowly Pulsating B star (SPB)
  ستاره‌ی ِ آهسته تپنده‌ی ِ گونه‌ی ِ B   
setâre-ye âhesté tapande-ye gune-ye B

Fr.: étoile B pulsante à longue période   

A member of a class of → B stars that are situated along the → main sequence with → spectral types ranging from B2 to B9 and masses from 3 to 7 → solar masses. In the → H-R diagram the SPB group lies below → beta Cephei variables, which are more massive. SPBs show light and line-profile variations that are multi-periodic with periods of the order of days. This variability is understood in terms of non-radial → stellar pulsations, and their → oscillation modes are high-order → g modes. Theoretical models attribute the pulsational nature of SPBs to the → kappa mechanism, acting in the metal → opacity bump at 2 x 105 K. Their g-mode pulsations penetrate deep into the stellar interior, making these objects very promising for → asteroseismology. Several oscillation modes are excited simultaneously, resulting in periodicities on time scales of the order of months or even years. The prototype of this group is 53 Per. First introduced as a distinct class by Waelkens (1991, A&A 246, 453).

slow; → pulsating; → B star.

solar-like star
  ستاره‌ی ِ خورشیدمانند   
setâre-ye xoršid-mânand

Fr.: étoile semblable au soleil   

A member of a very broad class of stars in which is found a mixture of late F, early, middle, and, sometimes, late G type dwarfs and sub-giants. See also → solar analog; → solar twin.

solar; → -like; → star.

South Pole Star
  ستاره‌ی ِ قطب ِ دشتر   
setâre-ye qotb-e daštar

Fr.: étoile du pôle sud   

A star that would mark the south → celestial pole. Presently no bright visible star is situated along the → rotation axis of the Earth in the southern hemisphere. But, because of the Earth's → axial precession, about 7,000 years from now the star → Delta Velorum in the constellation → Vela, the Sail, will come to within 0.2 degrees of the South Celestial Pole (around the year 9250 B.C.). That is closer to marking the celestial pole than → Polaris or → Sirius ever do during their reigns as pole stars! Sirius will become the South Pole Star some 60 thousand years from now (around the year 66270 B.C.). In that time, Sirius will come to within 1.6 degrees of the South Celestial Pole.

south; → celestial; → pole.

specific star formation rate (sSFR)
  نرخ ِ آبیزه‌ی ِ دیسش ِ ستارگان   
nerx-e âbize-ye diseš-e setâregân

Fr.: taux de formation d'étoiles spécifique   

Star formation rate per unit → mass. More specifically, the → star formation rate in a galaxy divided by the → stellar mass of the galaxy. Observations of galaxies over a wide range of → redshifts suggest that the slope of the SFR-M* relation is about unity, which implies that their sSFR does not depend strongly on stellar mass. Specific star formation rates increase out to z ~ 2 and are constant, or perhaps slowly increasing, from z = 2 out to z = 6, though with a large scatter, sSFR ~ 2-10 Gyr-1 (Lehnert et al., 2015, A&A 577, A112, and references therein).

specific; → star; → formation; → rate.

spinstar
  چرخاستاره   
carxâsetâré

Fr.: spinstar   

A hypothetical, very rapidly → rotating star formed in the → metal-deficient conditions of the primordial → interstellar medium. The → first stars were probably spinstars, because the lack of metals leads to faster rotation velocities. Indeed → metal-poor stars are more compact than → metal-rich ones. Stars formed from a gas whose → metallicity is below 1/2000 of the → solar metallicity could attain rotation velocities of 500-800 km s-1 (see also → Population III star). Rotation triggers → mixing processes inside the star, leading to the production of important quantities of 14N, 13C, and 22Ne (Maeder & Meynet 2012, and references therein). The production of primary 22Ne has an important impact on the → s-process  → nucleosynthesis in spinstars compared to non-rotating stars. This increases by orders of magnitude the s-process → yields of → heavy elements. Spinstars would therefore have strongly influenced the properties and appearance of the first galaxies that formed in the → Universe (See G. Meynet et al. 2009, arXiv:0709.2275; C. Chiappini, 2013, Astron. Nachr. /AN 334, No. 6, 595 and references therein).

spin; → star.

standard stars
  ستارگان ِ استانده   
setâregân-e estândé

Fr.: étoiles standard   

Stars for which accurate color indices and/or magnitudes exist, defining a standard system.

standard; → star.

star
  ستاره   
setâré (#)

Fr.: étoile   

A huge mass of hot gas whose radiation is provided by its internal → thermonuclear reactions. A star represents a → hydrodynamic equilibrium between two opposing forces, the inward → gravitational force, which is attempting to make the mass collapse and the pressure caused by the generation of nuclear energy. Below a certain mass (0.08 → solar masses), the central pressures and temperatures are insufficient to trigger the → hydrogen fusion (→ brown dwarf). Stars have a variety of masses and sizes. → Massive stars are less common than → low-mass stars (→ initial mass function). → Star formation results from → gravitational collapse of → molecular clouds (→ fragmentation; → pre-stellar core; → protostar; → accretion). After leaving the → main sequence, they pass through several evolutionary stages (e.g., → red giant, → supergiant, → white dwarf, → supernova, → neutron star) depending on their initial masses. See also: → internal structure of stars; → spectral classification; → luminosity class; → variable star; → multiple star. The term star is sometimes loosely applied to objects that do not comply with the above specifications, but are evolutionary products of stars, such as neutron stars and white dwarfs. For ancient civilizations a star was anything appearing in the night sky, apart from perhaps the Moon.

M.E. sterre, O.E. steorra; cf. O.S. sterro, O.N. stjarna, O.Fris. stera, Du. ster, O.H.G. sterro, Ger. Stern, Goth. stairno; cognate with Gk. aster, astron, L. stella (Fr. étoile, Sp. esterella, It. stella), Bret. sterenn, Pers. setâré, as below.

Setâré, variants star, estâr, estâré, and probably axtar, → astro-, (Lori, Laki) âsâra, (Laki) hasâra, (Tabari) essâra, (Baluci) istâr, (Ossetic) st'aly, (i)sthalu, (Tâti) usdurâ; Mid.Pers. stârag, stâr; Av. star-; cf. Skt. stár-, tāra-, tārakā- "star;" akin to Gk. and L., as above; PIE base *ster- "star."

star catalog
  کاتالوگ ِ ستارگان   
kâtâlog-e setâregân

Fr.: catalogue stellaire   

A listing of stars usually ordered by right ascension with observational data elements such as coordinates, magnitude, distance, proper motion, and so on.

star; → catalog.

star chart
  نگاره‌ی ِ ستارگان   
negâre-ye setâregân

Fr.: carte du ciel   

A chart or map showing the relative apparent positions of the stars as viewed from the Earth.

star; chart, from M.Fr. charte "card, map," from L. charta "leaf of paper, tablet," from Gk. khartes "layer of papyrus."

Negâré, from negâr "picture, figure," from negâštanPictor; setâregân plural of setâréstar.

star cluster
  خوشه‌ی ِ ستاره‌ای   
xuše-ye setâre-yi (#)

Fr.: amas stellaire   

1) A group of stars held together by the mutual → gravitational attraction of its members, which are physically related through common origin. They are of two types: → open clusters and → globular clusters.
2) A → bound stellar agglomeration for which the age of the stars exceeds the → crossing time (Giels & Portegies Zwart, 2010, MNRAS Letters, astro-ph/1010.1720). See also → stellar association

star; → cluster.

star count
  شمارش ِ ستاره، ~ ستارگان   
šomâreš-e setâré, ~ setâregân

Fr.: comptage d'étoiles   

The number of stars that appear in a given region of sky, usually counted on a photographic plate or CCD image.

star; → count.

star drift
  دلک ِ ستارگان   
delek-e setâregân

Fr.: dérive stellaire   

The relative motion of two groups of stars in the Galaxy moving in opposite directions.

star; → drift.

star formation
  دیسش ِ ستاره   
diseš-e setâré

Fr.: formation d'étoiles   

The process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy, star formation includes the study of the interstellar medium and molecular clouds as precursors to the star formation process as well as the study of young stellar objects.

star; → formation.

star formation efficiency (SFE)
  کارایی ِ دیسش ِ ستاره   
kârâyi-ye diseš-e setâré

Fr.: efficacité de formation d'étoiles   

The degree to which stars form in a system, such as a → molecular cloud or a → galaxy. It is given by the ratio of the total mass of stars to the initial gas mass: εSFE = Mstars / (Mstars + Mgas).

star formation; → efficiency.

star formation history
  تاریخ ِ دیسش ِ ستاره   
târix-e diseš-e setâré

Fr.: histoire de formation d'étoiles   

The → star formation rate as a function of time.

star; → formation; → history.

star formation quenching
  اسرش ِ دیسش ِ ستارگان   
osereš-e diseš-e setâregân

Fr.: assèchement de formation d'étoiles   

The premature termination of star formation process in some galaxies. The ultimate quenching of star formation is caused by stripping of the gas reservoir which will finally turn into stars. A wide variety of mechanisms have been proposed to provide quenching. For example, → major mergers can transform spiral galaxies into ellipticals, and may also quench future star formation by ejecting the → interstellar medium from the galaxy via starburst, → active galactic nucleus, or shock-driven winds. In rich clusters, where merging is less efficient because of the large relative velocities of galaxies, rapid encounters or fly-bys may cause the formation of a bar and growth of a spheroidal component instead of larger scale star formation. Also, cold gas can be stripped out of the galaxy both by tidal forces and ram pressure in the intracluster medium. Similarly, the hot halo that provides future fuel for cooling and star formation may be efficiently stripped in dense environments, thus quenching further star formation (see, e.g., Kimm et al., 2009, MNRAS 394, 1131, arXiv:0810.2794).

star; → formation; → quench.

star formation rate
  نرخ ِ دیسش ِ ستاره   
nerx-e diseš-e setâré

Fr.: taux de formation d'étoiles   

The rate at which a molecular cloud or a galaxy is currently converting gas into stars. It is given by the ratio of the number of stars to the star formation time-scale.

star formation; → rate.

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