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: 1347
stellar bar
  میله‌ی ِ ستاره‌ای   
mile-ye setâre-yi

Fr.: barre stellaire   

A bar-shaped accumulation of stars in galaxies, created by → density waves in a → spiral galaxy. → galactic bar, → barred spiral galaxy.

stellar; → bar.

stellar black hole
  سیه‌چال ِ ستاره‌ای   
siyah câl-e setâre-yi

Fr.: trou noir stellaire   

A → black hole with a mass in the range 3-30 → solar masses representing the end-product of → massive star evolution. Since → neutron stars cannot have masses larger than 3 solar masses, compact objects more massive than this must be black holes. There is good observational evidence for the existence of stellar black holes, based in particular on dynamical measurements of the masses of compact objects in → transient X-ray sources. Same as → stellar-mass black hole.

stellar; → black; → hole.

stellar complex
  همتافت ِ ستاره‌ای   
hamtâft-e setâre-yi

Fr.: complexe stellaire   

Any of the largest stellar assemblages consisting of the groupings of → star clusters, → stellar associations, and individual stars with sizes of 300-1000 → parsecs and ages of up to 100 millions years. Most stellar complexes are physical entities containing objects of common origin and are the birth places of most star clusters and associations. The brightest and youngest complexes are well-known stellar superstructures that outline the Galactic → spiral arms, and also include → H II regions, → giant molecular clouds, and → neutral hydrogen clouds (Efremov, Y. N., 1996, The Origins, Evolutions, and Densities of Binary Stars in Clusters, ASP Conf. Series, Vol. 90).

stellar; → complex.

stellar creation function
  کریای ِ آفرینش ِ ستارگان   
karyâ-ye âfarineš-e setâregân

Fr.: fonction de création stellaire   

The number of stars born per unit area in the mass range log M to log M + d log M during the time interval t to t + dt. The integration of the creation function over time gives the → present-day mass function (Miller & Scalo, 1797, ApJSS 41, 513).

stellar; → creation; → function.

stellar cusp
  تیزه‌ی ِ ستاره‌ای   
tize-ye setâre-yi

Fr.: cuspide stellaire   

A steeply rising radial profile (→ cusp) in the number density of stars in the central region of a galaxy resulting from the gravitational influence of a central → supermassive black hole, as predicted by theoretical models. An important assumption of all cusp formation models is that the stellar cluster is in dynamical equilibrium in the black hole potential. This radial profile is usually characterized by a power law of the form n(r) ∝ r, with a slope that is steeper than that of a flat isothermal → core. For a single-mass stellar cluster, Bahcall & Wolf (1976) determined the dynamically relaxed cusp will have γ = 7/4. The presence of such a cusp is important observationally because it may represent a simple test for black holes in stellar systems where dynamical mass estimates are difficult, such as in the cores of galaxies. In the case of the Milky Way, several attempts have been done to probe the presence of such a stellar cusp. However, the presence of the cusp is not confirmed. For example, based on the late-type stars alone, Do et al. (2009, ApJ 703, 1323), show that γ is less than 1.0 at the 99.7% confidence level. This is consistent with the nuclear star cluster having no cusp, with a → core profile that is significantly flatter than that predicted by most cusp formation theories, and even allows for the presence of a central hole in the stellar distribution (See also Genzel et al., 2010, Rev.Mod.Phys. 82, 3121, also at astro-ph/1006.0064).

stellar; → cusp.

stellar dynamics
  توانیک ِ ستاره‌ای   
tavânik-e setâre-yi

Fr.: dynamique stellaire   

The field of astrophysics that describes systems of many → point mass particles whose mutual gravitational interactions determine their orbits. Theses systems include → star clusters, → globular clusters, and galaxies (→ galaxy) consisting of about 102-103, 104-106, and up to about 1012 members respectively. Stellar dynamics deals with systems in which each member contributes importantly to the overall gravitational field and is usually concerned with the statistical properties of many orbits. It can be compared to the → kinetic theory of gases developed in the late 19th century. In contrast, → celestial mechanics deals with systems where the gravitational force of a massive planet or star determines the orbits of its satellites.

stellar; → dynamics.

stellar evolution
  فرگشت ِ ستاره   
fargašt-e setâré

Fr.: évolution stellaire   

The gradual changes in physical state (spectrum, luminosity, temperature) and chemical composition that occurs during the life of a star.

stellar; → evolution.

stellar feedback
  بازخورد ِ ستاره‌ای   
bâzxord-e setâre-yi

Fr.: rétroaction stellaire   

The process whereby large quantities of → energy and → momentum are released into the gas surrounding → star formation regions in galaxies. More specifically, → massive stars inject → energy, → mass, and → metals back to the → interstellar medium through → stellar winds and → supernova explosions. Feedback inhibits further star formation either by removing gas from the galaxy, or by heating it to temperatures that are too high to form new stars. Observations reveal feedback in the form of → galactic-scale outflows of gas in galaxies with high → star formation rates, especially in the → early Universe. Feedback in faint, low-mass galaxies (→ low-mass galaxy) probably facilitated the escape of ionizing radiation from galaxies when the Universe was about 500 million years old, so that the hydrogen between galaxies changed from neutral to ionized, a process called → reionization (Dawn K. Erb, 2015, Nature, 9 July).

stellar; → feedback.

stellar interior
  درونه‌ی ِ ستاره   
darune-ye setâré

Fr.: intérieur stellaire   

That part of a star which lies below the photosphere.

stellar; → interior.

stellar luminosity
  تابندگی ِ ستاره   
tâbandegi-ye setâré

Fr.: luminosité stellaire   

The total amount of energy emitted by a star per unit time. According to the → Stefan-Boltzmann law, the stellar luminosity is given by: L* = 4πR*2σTeff4, where R* is radius, σ is the → Stefan-Boltzmann constant, and Teff is → effective temperature. A star's luminosity depends, therefore, on two factors, its size and its surface temperature. Stellar luminosity is measured either in ergs per second or in units of → solar luminosity or in → absolute magnitude. See also → luminosity class.

stellar; → luminosity.

stellar magnetic field
  میدان ِ مغناتیسی ِ ستاره‌ای   
meydân-e meqnâtisi-ye setâre-yi

Fr.: champ magnétique stellaire   

The → magnetic field associated with a star. Magnetic fields are common among stars of solar and lower masses. So far definitive detections of fields in stars with masses ~1.5 Msun have, for the most part, been made for objects having anomalous chemical abundances (e.g., the → chemically peculiar A and B stars). Recently, however, observations of cyclic variability in the properties of → stellar winds from luminous → OB stars have been interpreted as evidence for the presence of large-scale magnetic fields in the surface layers and atmospheres of these objects (→ magnetic massive star). These inferences have been bolstered by the unambiguous measurement of a weak (~ 360 G) field in the chemically normal B1 IIIe star → Beta Cephei. These results suggest that magnetic fields of moderate strength might be more prevalent among → hot stars than had previously been thought. At the present time, the origin of magnetism in massive stars is not well understood. If the magnetic field of a hot star is produced by → dynamo effect in the → convective core, then a mechanism for transporting the field to the stellar surface must be identified. The finite electrical conductivity of the envelope leads to the outward diffusion of any fields contained therein, but only over an extended period of time. Estimates indicate that for stars more massive than a few solar masses, the resistive diffusion time across the radiative interior exceeds the → main sequence lifetime. Another possibility is that dynamo fields are advected from the core to the surface by rotation-induced → meridional circulation (MacGregor & Cassinelli, 2002, astro-ph/0212224).

stellar; → magnetic; → field.

stellar mass
  جرم ِ ستاره‌ای   
jerm-e setâre-yi

Fr.: masse stellaire   

1) The quantity of mass contained in a star. It is usually expressed in terms of the → solar mass (Msun).
2) A component of the total mass of a → galaxy represented by the mass of all its stars.

stellar; → mass.

stellar metallicity
  فلزیگی ِ ستاره‌ای   
felezigi-ye setâre-yi

Fr.: métallicité stellaire   

The metallicity derived from observations of stars in galaxies. It is mainly based on spectral → absorption lines in → ultraviolet (UV) and optical ranges. Stellar metallicity is a direct measure of the amount of metals in a galaxy, since large part of heavy elements lies in its stars.

stellar; → metallicity.

stellar nucleosynthesis
  هسته‌هندایش ِ ستاره‌ای   
haste-handâyeš-e setâre-yi

Fr.: nucléosynthèse stellaire   

The → nuclear reaction process taking place inside stars, whereby → chemical elements are produced from pre-existing nuclei heavier than → hydrogen and → helium.

stellar; → nucleosynthesis.

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.

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