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: 12948 Search : far
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.

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.

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu coa coe coh col col col com com com com com com com com com con con con con con con con con con con con coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>