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: 491
Bayesian model averaging (BMA)
  میانگین-گیری ِ بیزی ِمدل   
miyângin-giri-ye Bayesi-e model

Fr.:   

An approach to model selection in which one bases inference on an average of all possible models instead of a single best model. The BMA is largely used in various branches of knowledge to properly account for model uncertainty in performing predictions.

Bayesian; → model; → average.

Be phenomenon
  پدیده‌ی ِ Be   
padide-ye Be

Fr.: phénomène Be   

The episodic occurrence of abrupt → mass loss in → Be stars resulting in → Balmer lines in emission and → infrared excess. The Be phenomenon results from a combination of a long-term secular effect and short-term instabilities, such as pulsation. The secular evolution brings the star close enough to the critical → break-up velocity, so that the additional velocity field due to the instability may allow some mass ejection (Maeder 2011).

Be star; → phenomenon.

Be star
  ستاره‌یِ Be   
setâre-ye Be

Fr.: étoile Be   

A hot star of → spectral type B showing → Balmer lines in emission. Be stars are fast rotators (spinning at about 200 km/sec) and have strong → stellar winds with important → mass loss.

B, referring to the spectral type; e for emission lines; → star.

beam
  تابه   
tâbé (#)

Fr.: 1) faisceau, 2) lobe, 3) tache de diffraction   

1) A collection of nearly parallel → light  → rays or a concentrated stream of → particles. See also → beam of light.
2) The area of the sky being observed at any one time by a → radio telescope.
3) The size of the → diffraction pattern; synonymous with point spread function.

M.E. beem, from O.E. beam "tree;" akin to O.H.G boum "tree," Ger. Baum.

Tâbé, from tâb; tâbidan "light; to shine" + noun suffix.

beam efficiency
  کار‌آیی ِ تابه   
kârâi-ye tâbé

Fr.: efficacité de lobe   

A parameter indicating the quality of an antenna as a direction measuring device. It is given by the ratio of the total received power contained in the main beam of an antenna to the total power (including the sidelobes); the same as main beam efficiency. See also → beamwidth.

beam; → efficiency.

beam of light
  تابه‌ی ِ نور   
tâbe-ye nur (#)

Fr.: faisceau lumineux   

A relatively large bundle of → rays of light. See also → pencil of light.

beam; → light.

beam of particles
  تابه‌ی ِ ذره   
tâbe-ye zarré

Fr.: faisceau de particules   

A narrow unidirectional flow of particles

beam; → particle.

beam splitter
  فاقگر ِ تابه   
fâqgar-e tâbé

Fr.: lame séparatrice   

A partially reflecting mirror which permits a part of the light beam to pass through and reflects the rest.

beam; splitter, from to split, from M.Du. splitten, from P.Gmc. *spl(e)it-, PIE *(s)plei- "to split, splice."

Fâqgar, from fâq "split, breach, division" + tâbébeam.

beam switching
  دگربانی ِ تابه   
degarbâni-ye tâbé

Fr.: permutation de lobe   

In single dish radio astronomy, any technique which forms the difference of signals received from two (or more) pointings on the sky without physically moving the main reflector of the antenna. By rapidly forming differences between sky positions that do and do not contain astronomical sources, beam switching can minimize the corruption of spectral baselines by non-idealities in the instrumental frequency response, or of continuum observations by atmospheric fluctuations.

beam; → switching.

beamwidth
  تابه-پهنا   
tâbe-pahnâ

Fr.: largeur de lobe   

The angle between the two directions in the main beam at which the power response has fallen to half its maximum value. → beam efficiency.

From → beam + → width.

Tâbe-pahnâ, from tâbé, → beam, + pahnâ "width," → broad.

beat
  زنش   
zaneš (#)

Fr.: battement   

The periodic and alternatively strengthening and weakening of two waves of similar frequencies when they interfere with one another. In particular, the soft and loud sounds created by the interference of two sound waves of similar frequencies.

M.E. beten, from O.E. beaten, from P.Gmc. *bautan; IER *bhau- "to strike."

Zaneš, noun from zan- present tense stem of zadan "to beat, strike" + verbal noun suffix. Zadan from Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *gwhen- "to strike, kill."

beat Cepheid
  کِفِیءوسی ِ زنشی   
kefeusi-ye zaneši

Fr.: céphéide à battement   

A Cepheid variable in which two or more almost identical periods of variability pass into and out of phase with each other, producing periodic amplitude fluctuations in their light curves. Beat periods are typically about 2 hours.

beat; → Cepheid.

beat frequency
  بسامد ِ زنش   
basâmad-e zaneš

Fr.: fréquence de battement   

One of the frequencies that results from the combination of two waves of slightly different frquencies. A beat frequency is equal to the absolute value of the difference between the two frequencies. An unknown frequency can be determined by beating it with a reference frequency. More specifically, when the two frequencies are superimposed, the phase difference will change with time and wave interference alternate between constructive and destructive. The alterations of intensity brings about a beat frequency.

beat; → frequency.

Beaufort scale
  مرپل ِ بوفورت   
marpel-e Beaufort

Fr.: échelle de Beaufort   

A system for estimating and reporting wind speeds which has 13 standardized categories and associated descriptions. The Beaufort scale ranges from 0 for complete calm to 12 for a cyclone. In this scale, the wind speed (in km/h) equals 3B1.5, where B is the Beaufort number of the wind. The scale was originally devised for use at sea but has subsequently been modified for use over land.

Named after Admiral Sir Francis Beaufort (1774-1857), who introduced the first version of the system in 1805; → scale.

beauty
  زیبایی   
zibâyi (#)

Fr.: beauté   

A combination of qualities that pleases the mind.

M.E. be(a)ute, from O.Fr. beautez, beltet "beauty, seductiveness, beautiful person" from V.L. bellitatem (nominative bellitas) "state of being handsome," from L. bellus "pretty, charming."

Zibâyi, from zibâ "beautiful," related to zib "beauty, elegance, ornament," zibidan "to suit, to adorn."

beaver
  بیدستر   
bidastar (#)

Fr.: castor   

A large, amphibious rodent of the genus Castor, having sharp incisors, webbed hind feet, and a flattened tail, noted for its ability to dam streams with trees, branches, etc. (Dictionary.com).

M.E. bever, O.E. beofor, befor; cognate with Ger. Biber; Av. bawra-, bawri- "beaver" (Mid.Pers. bawrak "beaver"); Skt. babhrav- "reddish-brown," babhrus- "mangoose," L. fiber "beaver" (Fr. bièvre "River of Beavers"); O.H.G. biorr; Lith. bêbrus; Rus. bobr "beaver."

Bidastar "beaver," of unknown origin.

because
  زیرا   
zirâ (#)

Fr.: parce que   

For the reason that; on account of.

M.E. bi cause "by cause," from O.E. bi "by" (akin to Du. bij, O.H.G. bi, Ger. bei, Goth. bi) + → cause.

Zirâ, variants azirâ, zirâk, azirâk, from Mid.Pers. êt rây cê or ê(t) râd cê "because," literally "this reason why;" from êd "this" (O.Pers. aita; Av. aēta "this;" cf. Skt. etá); rây, → reason; "what" (O.Pers/Av. ci- "what, any," collateral stem to ka- "who?, what?;" cf. Skt. ka-; Gk. po-; L. quo-; E. what, who; PIE *qwos/*qwes).

Becklin-Neugebauer object
  بر‌آخت ِ بکلین-نیوجباؤر   
barâxt-e Becklin-Neugebauer

Fr.: objet de Becklin-Neugebauer   

A compact infrared source in the Orion molecular cloud (OMC-1). It is thought to be a very dusty compact H II region surrounding a young B0 or B1 star.

After Eric Becklin (1940-), and Gerry Neugebauer (1932-) who discovered the object in 1967; → object.

become
  شدن   
šodan (#)

Fr.: devenir   

To come, change, or grow to be.

M.E. becumen; O.E. becuman "happen, come about," also "meet with, arrive;" akin to Du. bekomen, O.H.G. biqueman "obtain," Ger. bekommen, Goth. biquiman; from be- a prefix denoting several meanings, and → come.

Šodan "to become, to go, to pass, to change," from Mid.Pers. šudan, šaw- "to go;" Av. š(ii)auu-, šiyav- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro."

becquerel
  بکرل   
becquerel (#)

Fr.: becquerel   

The → SI unit of → radioactivity. One becquerel corresponds to the → disintegration of one atom per second. Abbreviation: Bq. → curie.

Named for the French physicist Henri Becquerel (1852-1908), who discovered radioactivity in 1896.

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