An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1279
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 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

stereography
  استریونگاری   
estereyonegâri

Fr.: stétéographie   

The process or art of depicting solid objects on a plane surface.

stereo- + → -graphy

stereoscope
  استریو-نما، برجسته‌نما   
estereyo-namâ, barjaste-namâ

Fr.: stéréoscope   

An optical instrument for viewing an overlapping pair of photographs (or perspective drawings) in order to see a three-dimensional image.

stereo-; → -scope.

sterile
  سترون   
setarvan (#)

Fr.: stérile   

Incapable of producing offspring; not producing offspring (Dictionary.com).

M.Fr. stérile "not producing fruit," from L. sterilis "barren, unproductive, unfruitful," from PIE *ster- "stiff, rigid, firm, strong."

Satarvan, literally "mule-like, resembling a mule," from setar, variant of astar, → mule, + -van similarity and attribution suffix.

sterile neutrino
  نوترینوی ِ سترون   
notrino-ye setarvan

Fr.: neutron stérile   

A hypothetical type of → neutrino which does not participate in the → weak interaction. It would arise only from ordinary neutrinos oscillating into a sterile form (singlet, right handed → helicity). The sterile neutrino is a candidate for the → dark matter. Sterile neutrinos might have been produced in primordial plasma in the → early Universe. The idea of sterile neutrino was first proposed by Bruno Pontecorvo (1967) in a paper which also discussed neutrino oscillations.

sterile; → neutrino.

Stern-Gerlach experiment
  آزمایش ِ اشترن-گرلاخ   
âzmâyeš-e Stern-Gerlach (#)

Fr.: expérience de Stern et Gerlach   

An experiment devised for measuring the → magnetic moment of → silver atoms. A → beam of silver atoms is directed between the → poles of a non-homogeneous → magnetic field. Contrarily to the prediction of the classical theory, the atoms divide into two distinct parts. One half of atoms are deflected up, the other half deflected down. The amount of deflection up or down is exactly of the same magnitude. Whether an individual atom is deflected up or down appears to be random. From a measurement of the → deflection, one can find the strength of the magnetic moment. This experience provides proof that there exist only two permitted orientations, called the → quantization of → spin.

In honor of Otto Stern (1888-1969), German physicist, Nobel laureate in Physics 1943, and Walter Gerlach (1889-1979), German physicist, who carried out the experiment in 1922. They used a beam of silver atoms from a hot oven because they could be readily detected on a photograph emulsion. Moreover, the silver atoms allowed studying the magnetic properties of a single electron because the atoms have a single outer electron; → experiment.

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