An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 493
biotic environment
  پرگیر ِ زیستیک   
pargir-e zistik

Fr.: environnement biotique   

Ecology: The environment consisting of living organisms, which interact with each other and with their non-living surroundings.

Biotic adj. of → biotics; of → environment.


Fr.: biotique   

The science concerned with the functions of life, or vital activity and force.

From biotic, from Gk. biotikos "of or pertaining to life," from → bio- + -tic a suffix equivalent in meaning to → -ic.

doqotbi (#)

Fr.: bipolaire   

Having two poles; having two opposite main structures or components.

Bipolar, from → bi- + → polar, from → pole.

Doqotbi, from do-, → bi-, + qotbi, → polar, from qotb, → pole.

bipolar flow
  تچان ِ دوقطبی   
tacân-e doqotbi

Fr.: flot bipolaire   

Same as → bipolar outflow.

bipolar; → flow.

bipolar jet
  شان ِ دوقطبی   
šân-e doqotbi

Fr.: jet bipolaire   

One of two beams of high-temperature, ionized gas ejected in two opposite directions associated with a → protostar. The collimated jets, a consequence of the → accretion process, can extend over distances of several → light-years.

bipolar; → jet.

bipolar nebula
  میغ ِ دوقطبی   
miq-e doqotbi

Fr.: nébuleuse bipolaire   

An interstellar cloud of ionized gas with two main lobes which lie symmetrically on either side of a central star. The bipolar shape is generally due to the ejection of material by the central star in opposing directions.

bipolar; → nebula.

bipolar outflow
  ا ُستچان ِ دوقطبی   
ostacân-e doqotbi

Fr.: flot bipolaire   

A flow of gaseous material in two opposite directions emanating from protostellar regions or from → evolved stars during the early post-→ AGB evolution. In protostellar regions → molecular outflows are pushed by → bipolar jets.

bipolar; → outflow.

Ostacân, → outflow; doqotbibipolar.

došekast (#)

Fr.: biréfringence   

A property of some crystalline materials (e.g. calcite, quartz) which have different indices of refraction associated with different crystallographic directions. Therefore, the crystal splits incident transmitted light into two beams, each polarized perpendicularly to the other. Also called double refraction.

Birefringence, from → bi- + refringence, from L. refringere "to break up," from → re- "back" + combination form of frangere "to break."

Došekast, from do- "two," → bi- + šekast "breaking," from šekastan "to break up," Mid.Pers. škastan, Av. skand- "to break."

  دوشکستگر، دوشکستی   
došekastgar, došekasti (#)

Fr.: biréfringent   

Of or relating to → birefringence.

birefringent filter
  پالایه‌ی ِ دوشکستی، ~ دوشکستگر   
pâlâye-ye došekastgar, ~ došekasti

Fr.: filtre biréfringent   

A type of narrow-band filter that uses the birefringence to produce selective absorption of polarized light.

birefringent; → filter.

birefringent vacuum
  خلأ ِ دوشکستگر   
xala'-e došekastgar

Fr.: vide biréfringent   

Empty space undergoing → vacuum birefringence.

birefringent; → vacuum.

Birkhoff's theorem
  فربین ِ بیرکهوف   
farbin-e Birkhoff

Fr.: théorème de Birkhoff   

For a four dimensional → space-time, the → Schwarzschild metric is the only solution of → Einstein's field equations which describes the gravitational field created by a spherically symmetrical distribution of mass. The theorem implies that the gravitational field outside a sphere is necessarily static, and that the metric inside a spherical shell of matter is necessarily flat.

The theorem was first demonstrated in 1923 by George David Birkhoff (1884-1944), an American mathematician; → theorem

  ۱) زایمان؛ ۲) زادمان، زاد؛ ۳) زایش   
1) zâymân; 2) zâdmân, zâd; 3) zâyeš

Fr.: 1) acouchement; 2;3 ) naissance   

1) The act or process of bearing or bringing forth offspring.
2) The act or fact of being born.
3) The coming into existence of something.

M.E. byrthe; O.E. gebyrd; cf. O.H.G. giburt, Ger. geburt; PIE *bhrto, from *bher- "to bear."

1) Zâymân, from zây present stem of zâyidan, zâdan "to give birth" (Mid.Pers. zâtan; Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" cf. Skt. janati "begets, bears;" Gk. gignesthai "to become, happen;" L. gignere "to beget," gnasci "to be born;" PIE base *gen- "to give birth, beget") + -mân a suffix forming verbal nouns, → organization.
2) Zâd, past stem of zâyidan, zâdan, as above; zâdmân with prefix -mân, as above.
3) Zâyeš, from zây, present stem of zâyidan + -eš suffix of verbal nouns, → -tion.

birth binary population (BBP)
  پرینش ِ دورین‌ها هنگام ِ زادمان   
porineš-e dorinhâ hengâm-e zâdmân

Fr.: population binaire à la naissance   

In star formation models, the population of binary components formed via random pairing of stars distributed according to the → canonical IMF.

birth; → binary; → population.


Fr.: ligne de naissance   

The path in the → H-R diagram that continuously → accreting stars follow. Stars on the birthline are difficult to observe, because they are hidden by the → accretion disk and a dense → cocoon of → interstellar matter. The star becomes visible once a sufficient amount of the surrounding matter has been dispersed. It follows that the young starsare observed generally between the birthline and the → zero-age main sequence (ZAMS). Before hydrogen ignition, gravitational contraction and deuterium burning are the main energy sources for the star. The localization of the birthline depends on the deuterium → accretion rate. First introduced by R. Behrend & A. Maeder, 2001 (A&A 373, 190).

birth; → line.

Biruni's method
  روش ِ بیرونی   
raveš-e Biruni

Fr.: méthode de Biruni   

A method devised by the Iranian astronomer Biruni (973-1048) to measure the Earth radius, using trigonometric calculations. In contrast to foregoing → Eratosthenes' method and → Mamun's method, which required expeditions to travel long distances, Biruni's method was on-site. He carried out the measurement when he was at Nandana Fort (at the southern end of the pass through the Salt Range, near Baghanwala in the Punjab). He first calculated the height of a hill (321.5 m). To do this he used the usual method of observing the summit from two places in a straight line from the hill top. He measured the distance, d, between the two places and the angles θ1 and θ2 to the hill top from the two points, respectively. He made both measurements using an astrolabe. The formula that relates these angles to the hill height is: h = (d. tan θ1 . tan θ2) / (tan θ2 - tan θ1). He then climbed to the hill top, where he measured the → dip angle (θ), that is the angle of the line of sight to the horizon. He applied the values he obtained for the dip angle and the hill's height to the following trigonometric formula to derive the Earth radius: R = h cosθ / (1 - cos θ). The result for the Earth radius was 12,851,369.845 cubits (or 6335.725 km, using favorable conversion units). Despite the fact that the method is very ingenious, such a precise value is only by chance, because of several drawbacks: The plane was not perfectly flat to serve as the smooth surface of the sea. A measuring instrument more accurate than the alleged 5 arc minutes was needed. And the method suffered from the → atmospheric refraction (See, e.g., Gomez, A. G., 2010, Journal of Scientific and Mathematical Research).

Abu Rayhân Mohammad Biruni (973-1048 A.D.), one of the greatest scholars of the medieval era, was an Iranian of the Khwarezm region; → method.

bismut (#)

Fr.: bismuth   

A white, crystalline, brittle metallic chemical element with a pinkish tinge; symbol Bi. → Atomic number 83; → atomic weight 208.9804; → melting point 271.3°C; → boiling point about 1,560°C; → specific gravity 9.75 at 20°C; → valence +3 or +5. Bismuth is the most → diamagnetic of all metals. Its thermal conductivity is lower than any metal, except → mercury. There is only one naturally occurring → isotope of bismuth, 209Bi. Bismuth is used in a number of very different applications, chiefly in bismuth alloys, and in pharmaceuticals and chemicals.

From Ger. Bismuth, Wismut, Wissmuth, probably from weisse Masse "white mass," indicating how the element appears in nature.


Fr.: bissextile   

Of or relating to a → leap year or to the extra day falling in a leap year.

L.L. bissextlis (annus) "year containing an intercalary day," from bisextus, from bis "twice, two, doubled" + sextus "sixth," because in the → Julian calendar the sixth day before the Calends of March was doubled every four years. Same as → leap and → intercalary day.

Andarheli, of or relating to andarhelintercalation.

Note. Some authors have used the Pers. term behizaki for "bissextile," however this is problematic as far as the calendar history is concerned. The term comes from Mid.Pers. vihezagig or vihezakik "movable," which was the name of the additional whole month of 30 days which Iranians used in their calendar system in the Sasanid era. In fact they did not use an intercalary day every four years, but instead added a whole month after a period of 120 years. The operation was called vihezag. The term originates from Mid.Pers. vihez- "to move, progress," vihezag(k) "movement, progression." Therefore, this dictionary cautions against equating behizaki and bissextile. → embolismic month.


Fr.: bistabilité   

The condition in which a physical system is capable of assuming either of two stable states.

bi-; → stable.

bistability jump
  جهش ِ دو-پایداری   
jaheš-e do-pâydâri

Fr.: bistabilité par saut   

An abrupt discontinuity in the → stellar wind properties of → hot stars near → effective temperatures about 21,000 K and 10,000 K, corresponding to O9.5-B3 supergiants (Castor et al. 1975, ApJ 195, 157; Lamers et al., 1995, ApJ 455, 269). At these temperatures the → terminal velocity of the wind drops steeply by about a factor two and the → mass loss rate increases steeply by about a factor three to five, when going from high to low temperatures. Bistability jump is related to the degree of ionization in the wind. With a little drop in the temperature, the dominant driving element (Fe) will recombine to lower ionization stages which produces a lower terminal velocity and a relatively high density in the wind. → wind momentum. Additional bistability jumps may occur at higher temperatures where CNO may provide the dominant line driving, especially for low metallicity stars (Vink et al. 2001, A&A 369, 574). However, a recent study using a larger sample finds that there is a gradual decline in the wind terminal velocities of early B supergiants and not a "jump" (Crowther et al. 2006, A&A 446, 279).

bistability; → jump.

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