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: 13176 Search : far
battery
  باتری   
bâtri (#)

Fr.: batterie   

A combination of → cells connected together so as to produce useful electrical energy.

M.Fr. batterie "a grouping of artillery pieces for tactical purposes," from O.Fr. baterie "beatng, thrashing, assault," from battre "to beat," from L. battuere "to beat."

Bâtri, loanword from Fr., as above.

bay
  باهه   
bâhé

Fr.: baie   

A body of water forming an indentation of the shoreline, larger than a cove but smaller than a → gulf (Dictionary.com).

M.E. baye, from M.Fr. baie, from L.L. bâia, perhaps ultimately from Iberian bahia.

Bâhé, loan from Sp. bahia.

Bayer designation
  نامگزینی ِ بایر   
nâmgozini-ye bayer

Fr.: designation de Bayer   

A stellar designation system in which a specific star is identified by a Greek letter, followed by the genitive form of its hosting → constellation's Latin name. For example, Alpha Eridani, Delta Cephei, Lambda Bootis. The Greek alphabet has only 24 letters. In case a single constellation contained a larger number of stars, Bayer amended with Latin letters: upper case A, followed by lower case b through z (omitting j and v), for a total of another 24 letters. Bayer did not go beyond z, but later astronomers added more designations using both upper and lower case Latin letters, the upper case letters following the lower case ones in general. Examples include, for Vela: a Vel (Velorum), z Vel, A Vel, Q Vel; for Scorpius: d Sco (Scorpii), A Sco; for Leo: b Leo (Leonis), o Leo, A Leo, → c Orionis. Compare with the → Flamsteed designation.

First introduced by Johann Bayer (1572-1625) in his atlas Uranometria, published in 1603 at Augsburg, Germany; → designation.

Bayes' theorem
  فربین ِ بیز   
farbin-e Bayes

Fr.: théorème de Bayes   

A theorem in probability theory concerned with determining the → conditional probability of an event when another event has occurred. Bayes' theorem allows revision of the original probability with new information. Its simplest form is: P(A|B) = P(B|A) P(A)/P(B), where P(A): independent probability of A, also called prior probability; P(B): independent probability of B; P(B|A): conditional probability of B given A has occurred; P(A|B): conditional probability of A given B has occurred, also called posterior probability. Same as Bayes' rule.

Named after its proponent, the British mathematician Reverend Thomas Bayes (1702-1761). However, Bayes did not publish the theorem during his lifetime; instead, it was presented two years after his death to the Royal Society of London.

Bayesian
  بیزی   
Bayesi

Fr.: bayésien   

Being, relating to, or denoting statistical methods based on → Bayes' theorem.

Referring to → Bayes' theorem.

Bayesian inference
  دربرد ِ بیزی   
darbord-e Bayesi

Fr.: inférence bayésienne   

An approach to → statistical analysis in which → unknowns to be estimated have a prior → probability distribution which combined with the information from data produces a posterior probability distribution for the target quantities.

Bayesian; → inference.

Bayesian model
  مدل ِ بیزی   
model-e Bayesi

Fr.: modèle bayésien   

A mathematical framework described by the prior distribution of a random parameter and by the likelihood of the observations. In this framework, all information on the random parameter based on the observations is included in the posterior distribution which can be obtained using → Bayes' theorem (see, e.g., Andrieu et al., 2001, "An Introduction to Monte Carlo Methods for Bayesian Data Analysis," in Nonlinear Dynamics and Statistics, ed. A. I. Mees, Boston: Birkhäuser).

Bayesian; → model.

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.


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