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: 1281
Scheat (β Peg)
  اسب-شانه   
Asb-šâné

Fr.: Scheat   

The second-brightest star in the constellation → Pegasus. It is a giant star of spectral type M2.5 II-III whose magnitude varies between 2.3 and 2.7.

Scheat, from Ar. as-sâq "leg," erroneously taken from the Ar. name of δ Aquarii as-sâq al-sâkib al-ma' (الساق الساکب‌الماء) "the leg of the water-bearer."

Asb-šâné, literally "the Horse's Shoulder," from asbhorse + šâné "shoulder" (Lori šona, Kurd. šân, Gilaki cân, con), maybe related to Skt. skandhá- "shoulder, trunk of tree, bulk" (Pali khandha-, Ashkun kándä, Bashkarih kân, Tôrwâldi kan "shoulder"), from skand- "to jump, leap, spring out," skandati "he jumps;" cf. L. scandere "to climb."

Schechter function
  کریای ِ ششتر   
karyâ-ye Schechter

Fr.: fonction de Schechter   

A mathematical expression that describes the → luminosity function of galaxies. The function correctly reflects the facts that the luminosity function decreases with increasing luminosity and that the decrease is particularly marked at high luminosities. It is expressed as: φ(L) = φ*(L/L*)α exp (-L/L*), which has two parts and three parameters: φ* is an empirically determined amplitude, α is an empirically derived exponent, and L* is a characteristic luminosity which separates the low and high luminosity parts. For small luminosities (L much smaller than L*) the Schechter function approaches a power law, while at high luminosities (L much larger than L*) the frequency of galaxies drops exponentially. φ*, L*, and the faint-end slope α depend on the observed wavelength range, on the → redshift, and on the environment where the galaxies are observed.

Named after the American astronomer Paul Schechter (1948-), who proposed the function in 1976 (ApJ 203, 297); → function.

Schmidt law
  قانون ِ اشمیت   
qânun-e Schmidt

Fr.: loi de Schmidt   

A power-law relation between → star formation rate (SFR) and a corresponding measure of gas density. For external galaxies it is usually expressed in terms of the observable surface density of gas (Σgas): SFR ∝ Σgasn. The exponent n is determined to be 1.4 ± 0.15 (Kennicutt 1998, ApJ 498, 541). The validity of the Schmidt law has been tested in dozens of empirical studies. The Schmidt law provides a tight parametrization of the global star formation law, extending over several orders of magnitude in SFR and gas density.

Named after Maarten Schmidt (1929-), a dutch-born American astronomer, who also discovered the first → quasar (3C 273) in 1963.

Schmidt telescope
  تلسکوپ ِ اشمیت، دوربین ِ ~   
teleskop-e Schmidt, durbin-e ~ (#)

Fr.: télescope de Schmidt   

A telescope with a spherical concave primary mirror in which the aberration produced by the spherical mirror is compensated for by a thin correcting lens placed at the opening of the telescope tube. Its very wide-field performance makes it suitable for surveys.

Named after Bernhard Woldemar Schmidt (1879-1935), a German optician of Estonian origin, who invented the telescope in 1930; → telescope.

Schmidt-Cassegrain telescope
  تلسکوپ ِ اشمیت-کاسگرن، دوربین ِ ~   
teleskop-e Schmidt-Cassegrain, durbin-e ~ (#)

Fr.: télescope Schmidt-Cassegrain   

A mixture of the → Cassegrain telescope with a very short → focal length and of a Schmidt design (due to the presence of the → corrective plate), used mainly in → amateur astronomy. The main advantage of this telescope is its compact design. However, Schmidt-Cassegrain telescopes produce fainter images with less contrast than other telescope designs with similar → aperture sizes. This is due to the comparatively large → secondary mirror required to reflect the light back the → eyepiece.

Schmidt telescope; → Cassegrain telescope.

Schmidt-Kennicutt relation
  باز‌آنش ِ اشمیت-کنیکات   
bâzâneš-e Schmidt-Kennicutt

Fr.: relation Schmidt-Kennicutt   

Same as the → Schmidt law.

Named after the American astrophysicists Maarten Schmidt (1929-), the pioneer of research in this field, and Robert C. Kennicutt, Jr. (1951-), who developed the study; → relation.

scholar
  دانش‌پژوه، دانشور   
dânešpažuh, dânešvar (#)

Fr.: 1) lettré, érudit; 2) boursier   

1) A learned or erudite person, especially one who has profound knowledge of a particular subject. → scientist.
2) A student who has been awarded a scholarship.

M.E. scoler(e); O.E. scolere "student," from M.L. scholaris, from L.L. scholaris "of a school," from L. schola, from Gk. skhole "school, lecture, discussion; leisure, spare time."

Dânešpažuh, from dânešscience + pažuh agent noun of pažuhidan "to search," → research. Dânešvar, from dâneš, as befor, + -var possession suffix.

Schottky barrier
  ورغه‌ی ِ شوتکی   
varqe-ye Schottky

Fr.: barrière de Schottky   

A junction between a metal and a semiconductor, which exhibits rectifying characteristics. A Schottky barrier has a very fast switching action and low forward voltage drop of about 0.3 volts, compared with 0.6 volts in silicon diodes, which use adjacent p-type and n-type semiconductors.

Named after Walter Hans Schottky (1886-1976), German physicist, who described the phenomenon; → barrier.

Schottky defect
  آک ِ شوتکی   
âk-e Schottky

Fr.: défaut de Schottky   

An unoccupied position in a crystal lattice which forms when oppositely charged ions leave their lattice sites, creating vacancies.

Named after Walter Hans Schottky (1886-1976), German physicist; → defect.

Schottky diode
  دیود ِ شوتکی   
diod-e Schottky (#)

Fr.: diode Schottky   

A → semiconductor diode containing a → Schottky barrier. Such a diode has a low forward voltage drop and very fast switching characteristics. Also called Schottky barrier diode and hot electron diode.

Schottky barrier; → diode.

Schottky noise
  نوفه‌ی ِ شوتکی   
nufe-ye Schottky

Fr.: bruit de Schottky   

Excess voltage generated by random fluctuations in the emission of electrons from a hot cathode, causing a hissing or sputtering sound (shot noise) in an audio amplifier and causing snow on a television screen. Same as → shot effect, → shot noise.

Named after Walter Hans Schottky (1886-1976), German physicist; → noise.

Schrödinger equation
  هموگش ِ شرودینگر   
hamugeš-e Schrödinger

Fr.: équation de Schrödinger   

A fundamental equation of physics in → quantum mechanics the solution of which gives the → wave function, that is a mathematical expression that contains all the information known about a particle. This → partial differential equation describes also how the wave function of a physical system evolves over time.

Named after Erwin Schrödinger (1887-1961), the Austrian theoretical physicist, Nobel Prize 1933, who first developed the version of quantum mechanics known as → wave mechanics; → equation.

Schrödinger's cat
  گربه‌ی ِ شرودینگر   
gorbe-ye Schrödinger (#)

Fr.: chat de Schrödinger   

A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics. A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an → alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat's fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, "observes" the cat, and "collapses" its wave function. However, Schrödinger's argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore "observed" by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function.

Named after Erwin Schrödinger (1887-1961), → Schrödinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta "cat."

Gorbé, from Mid.Pers. gurbag "cat;" → Schrodinger equation,

Schröter's effect
  اُسکر ِ شروتر   
oskar-e Schröter

Fr.: effet de Schröter   

A phenomenon in which the observed and predicted phases of Venus do not coincide. At eastern elongation, when the planet is visible in the evening sky, dichotomy (half-phase) usually comes a day or two earlier than predicted, while at western elongation dichotomy occurs a day or two later.

Named after Johan Schröter (1745-1816), German astronomer, who first described the effect in 1793; → effect.

Schrodinger equation
  هموگش ِ شرودینگر   
hamugeš-e Schrödinger

Fr.: équation de Schrödinger   

A fundamental equation of physics in → quantum mechanics the solution of which gives the → wave function, that is a mathematical expression that contains all the information known about a particle. This → partial differential equation describes also how the wave function of a physical system evolves over time.

Named after Erwin Schrödinger (1887-1961), the Austrian theoretical physicist, Nobel Prize 1933, who first developed the version of quantum mechanics known as → wave mechanics; → equation.

Schrodinger's cat
  گربه‌ی ِ شرودینگر   
gorbe-ye Schrödinger (#)

Fr.: chat de Schrödinger   

A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics. A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an → alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat's fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, "observes" the cat, and "collapses" its wave function. However, Schrödinger's argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore "observed" by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function.

Named after Erwin Schrödinger (1887-1961), → Schrodinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta "cat."

Gorbé, from Mid.Pers. gurbag "cat;" → Schrodinger equation,

Schroter's effect
  اُسکر ِ شروتر   
oskar-e Schröter

Fr.: effet de Schröter   

A phenomenon in which the observed and predicted phases of Venus do not coincide. At eastern elongation, when the planet is visible in the evening sky, dichotomy (half-phase) usually comes a day or two earlier than predicted, while at western elongation dichotomy occurs a day or two later.

Named after Johan Schröter (1745-1816), German astronomer, who first described the effect in 1793; → effect.

Schwarzschild barrier
  ورغه‌ی ِ شو‌آرتسشیلد   
varqe-ye Schwarzschild

Fr.: barrière de Schwarzschild   

An upper theoretical limit to the → eccentricity of orbits near a → supermassive black hole (SBH). It results from the impact of → relativistic precession on the stellar orbits. This phenomenon acts in such a way as to "repel" inspiralling bodies from the eccentric orbits that would otherwise lead to capture as → extreme mass ratio inspiral (EMRI)s. In other words, the presence of the Schwarzschild barrier reduces the frequency of EMRI events, in contrast to that predicted from → resonant relaxation. Resonant relaxation relies on the orbits having commensurate radial and azimuthal frequencies, so they remain in fixed planes over multiple orbits. In the strong-field potential of a massive object, orbits are no longer Keplerian but undergo significant perihelion precession. Resonant relaxation is only efficient in the regime where precession is negligible. The Schwarzschild barrier refers to the boundary between orbits with and without significant precession. Inside this point resonant relaxation is strongly quenched, potentially reducing inspiral rates.

Schwarzschild black hole; → barrier.

Schwarzschild black hole
  سیه‌چال ِ شو‌آرتسشیلد   
siyahcâl-e Schwarzschild

Fr.: trou noir de Schwarzschild   

A → black hole with zero → angular momentum (non-rotating) and zero electric charge derived from Karl Schwarzschild 1916 exact solution to Einstein's vacuum → field equations.

Karl Schwarzschild (1873-1916), German mathematical physicist, who carried out the first relativistic study of black holes. → black hole.

Schwarzschild metric
  متریک ِ شو‌آرتسشیلد   
metrik-e Schwarzschild

Fr.: métrique de Schwarzschild   

In → general relativity, the → metric that describes the → space-time outside a static mass with spherically symmetric distribution.

Schwarzschild black hole; → metric.

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