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: 13048 Search : far
stellar object
  بر‌آخت ِ ستاره‌ای   
barâxt-e setâre-yi

Fr.: objet stellaire   

Any of a class of → astronomical objects which is thought to evolve into a → star or is a descendant of a star.

stellar; → object.

stellar parallax
  دیدگشت ِ ستاره   
didgašt-e setâré

Fr.: parallaxe stellaire   

The apparent → difference in the → position of a → celestial object as seen by an → observer from two widely separated → locations. The parallax of an object can be used to derive its → distance. The relationship between the → parallax angle  p (measured in seconds of arc) and the distance d (measured in → astronomical units) is given by d = 206,264 / p. For a parallax angle p = 1'', the distance to the star would correspond to 206,264 AU. By convention, the distance unit → parsec is defined to be equivalent to 206,264 AU. Therefore, the parallax relation takes the much simpler form: d (in pc) = 1/p (in seconds of arc). The first star whose parallax was measured was → 61 Cygni (Bessel, 1838).
See also:
annual parallax, → diurnal parallax, → dynamical parallax, → geocentric parallax, → heliocentric parallax, → horizontal parallax, → lunar parallax, → mean parallax, → parallactic ellipse, → parsec, → photometric parallax, → secular parallax, → solar parallax, → spectroscopic parallax, → statistical parallax, → trigonometric parallax.

stellar; → parallax.

stellar photometry
  نورسنجی ِ ستاره‌ای   
nursanji-ye setâre-yi

Fr.: photométrie stellaire   

The precise measurement of a star's brightness, usually through several specific wavelength bands.

stellar; → photometry.

stellar physics
  فیزیک ِ ستاره‌ای   
fizik-e setâre-yi (#)

Fr.: physique stellaire   

Same as → stellar astrophysics.

stellar; → physics.

stellar population
  پُرینش ِ ستاره‌ای   
porineš-e setâre-yi

Fr.: population stellaire   

Population I star; → Population II star.

stellar; → population.

stellar population synthesis
  هندایش ِ پرینش‌های ِ ستاره‌ای   
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.

stellar; → population; → model.

stellar pulsation
  تپش ِ ستاره، ~ ستاره‌ای   
tapeš-e setâré, ~ setâre-yi

Fr.: pulsation stellaire   

The expansion of a star followed by contraction so that its → surface temperature and → luminosity undergo periodic variation. Pulsation starts with a loss of → hydrostatic equilibrium, when, for example, a layer contracts. This layer heats up and becomes more opaque to radiation. Therefore, radiative diffusion slows down through the layer because of its increased → opacity and heat increases beneath it. Hence pressure rises below the layer. Eventually this increase in pressure starts to push the layer out. The layer expands, cools and becomes more transparent to radiation. Energy now escapes from below the layer and the pressure beneath the layer drops. The layer falls inward and the cycle starts over. See also → kappa mechanism; → gamma mechanism; → partial ionization zone; → pulsating star; → valve mechanism.

stellar; → pulsation.

stellar rotation
  چرخش ِ ستاره، ~ ستاره‌ای   
carxeš-e setâré, é setêre-yi

Fr.: rotation stellaire   

The spinning of a star about its axis, due to its angular momentum. Stars do not necessarily rotate as solid bodies, and their angular momentum may be distributed non-uniformly, depending on radius or latitude.Thus the equator of the star can rotate at a different angular velocity than the higher latitudes. These differences in the rate of rotation within a star may have a significant role in the generation of a stellar magnetic field.

stellar; → rotation.

stellar structure
  ساختار ِ ستاره، ~ ستاره‌ای   
sâxtâr-e setâré, ~ setêre-yi

Fr.: structure stellaire   

A physical model that describes the internal arrangement of a star in detail and makes detailed predictions about the luminosity, the color, and the future evolution of the star.

stellar; → structure.

stellar structure equation
  هموگش ِ ساختار ِ ستاره   
hamugeš-e sâxtâr-e setâré

Fr.: équation de structure stellaire   

A set of → differential equations describing the physical properties of stars based on two main assumptions: a star is a perfect sphere and the net force on a macroscopic mass element is zero. If the effects of rotation and magnetism are ignored, these assumptions lead to a set of five differential equations.

stellar; → structure; → equation.

stellar system
  راژمان ِ ستاره‌ای   
râžmân-e setâre-yi

Fr.: système stellaire   

A system comprised of a group of stars bound by → gravitational attraction. Same as → star system.

stellar; → system.

stellar wind
  باد ِ ستاره‌ای   
bâd-e setâre-yi

Fr.: vent stellaire   

The steady flow of gas away from a star resulting in → mass loss. They range from gentle solar wind (2 x 10-14 solar masses per year) to violent winds some 10 billions times stronger (10-4 solar masses per year) for hot, massive stars.

stellar; → wind.

stellar-mass black hole
  سیه‌چال با جرم ِ ستاره‌ای   
siyah câl bâ jerm-e setâre-y

Fr.: trou noir de masse stellaire   

Same as → stellar black hole.

stellar; → mass; → black; → hole.

step function
  کریای ِ پله‌ای   
karyâ-ye pelle-yi

Fr.: fonction échelon   

Math.: A function f of a real variable defined on an interval [a,b] so that [a,b] can be divided into a finite number of sub-intervals on each of which f is a constant. The graph of a step function is a series of line segments resembling a set of steps.

Step, from M.E. steppen, O.E. steppan; cf. Du. stap, O.H.G. stapfo, Ger. stapfe "footprint;" → function.

Karyâ, → function; pellé "stair, step;" Mid.Pers. pylg "step," pillagân "steps, staircase;" from *palak, from *padak, from pad-, → foot, + relation suffix -ak.

Stephan's Quintet
  پنج‌تایه‌ی ِ استفان   
panjtâye-ye Stephan

Fr.: Quintet de Stéphan   

A group of five closely grouped galaxies (NGC 7317, 7318A, 7318B, 7319 and 7320) in the constellation → Pegasus. Four of the galaxies show essentially the same → redshift, suggesting that they are at the same distance from us. The fifth galaxy (NGC 7320) has a smaller redshift than the others, indicating it is much closer. This one is probably a foreground galaxy which happens to lie along the line of sight. The four distant galaxies seem to be colliding, showing serious distortions due to gravitational → tidal forces. The NASA → Spitzer Space Telescope has revealed the presence of a huge intergalactic → shock wave. Collisions play an important role in the life cycles of galaxies. → merging galaxies.

Named after the French astronomer Edouard Stéphan (1837-1923), who discovered the group in 1877 at Marseilles Observatory, using the → Foucault's reflector; → quintet.

steradian (sr)
  استرادیان   
esterâdiân (#)

Fr.: stéradian   

The solid angle subtended at the center of a sphere by an area on its surface numerically equal to the square of the radius. → square degree.

From ste(reo)-, → stereo- + → radian.

stere-, stereo-
  استریو-   
estereyo- (#)

Fr.: stéréo-   

A combining form meaning "having and dealing with three dimensions of space; solid."

From stereo a shortening of stereotype, from Fr. stéréotype (adj.) "printing by means of a solid plate of type," from Gk. stereos "solid."

Loan from Fr., as above.

stereo-comparator
  هم‌سنج‌گر ِ استریو   
ham-sanj-gar-e estereyo

Fr.: stéréo comparateur   

A device that allows two images of the sky taken at different times to be optically superimposed so that changes in star brightness or moving objects can be detected.

stereo-; comparator, from L. comparare "to place together, match," from compar "alike, matching," → com-; → partial + -tor.

Ham-sanj-gar "comapartor," from ham-, → com-, + sanj stem of sanjidan "to compare" + -gar, → -or; → stereo-.

stereographic
  استریونگاری، استریونگاریک   
estereyonegâri, estereyonegârik

Fr.: stétéographique   

Of, relating to, or being a delineation of the form of a solid body on a plane.

stereography; → -ic

stereographic projection
  فراشانش ِ استریونگاریک   
farâšâneš-e estereyonegârik

Fr.: projection stéréographique   

A graphical method of depicting three-dimensional geometrical objects in two dimensions. In a → planispheric astrolabe, it is the projection of a point of the celestial sphere onto the equatorial plane, as seen from one of the poles. The center of projection is the South pole for the northern hemisphere, and the North pole for the southern hemisphere. In this operation the projection of any circle of the sphere remains a circle on the projection plane and moreover the projection does not alter angles.

stereographic; → projection

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu Coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>