An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < B r bac Bal Bar bar bea beh Bes bia Big bin bin bip Bla bla bli blu Boh Bon Bot bow bre bri bro bur > >>

Number of Results: 486
break luminosity
  تابندگی ِ بره   
tâbandegi-ye boré

Fr.: luminosité de coupure   

A characteristic luminosity around which the → luminosity function of a sample of galaxies changes to a steeper slope or exponentially declines.

break; → luminosity.

break-up velocity
  تندای ِ گسست   
tondâ-ye gosast

Fr.: vitesse de rupture   

The velocity of a → rotating star at which the → centrifugal force equals the → gravitational force. Also known as → critical velocity. The simplest expression of the break-up velocity for an OB star, ignoring the → Eddington luminosity, is given by the relation: v = (GM / R)1/2, where M and R are the mass and radius of the star respectively, and G the → gravitational constant. A more realistic expression takes into account not only the → radiation pressure, but also the non-uniformity of the brightness over the stellar surface, as indicated by → von Zeipel theorem. With these conditions, the break-up velocity has a more complicated formula, corresponding to the velocity reached when somewhere on the star the → total gravity becomes zero.

break + up; M.E.; O.E. up, uppe, → hyper-; → velocity.

bereš (#)

Fr.: brèche   

A rock composed of angular fragments (over two millimeter diameter) of older rocks melded together with a matrix of smaller particles or a mineral cement.

From It. breccia "broken (rock)," from a Germanic source akin to O.H.G. brecha "a breaking," ultimately from PIE *bhreg- "to break," → fraction.

Bereš, loan from Fr.


Fr.: bréchifier   

To form as → breccia.

From → breccia + → -ate.

  برشیده، برشمند   
berešidé, beršmand

Fr.: bréchifié   

Characterized by, converted into, or resembling a breccia; especially of a rock structure marked by an accumulation of angular fragments, or of an ore texture showing mineral fragments without notable rounding.

breccia, → brecciated.

brecciated rock
  سنگ ِ برشیده   
sang-e berešidé

Fr.: roche bréchifiée   

A rock formed by the process of → brecciation.

brecciated; → rock.


Fr.: bréchification   

The formation of → breccia.

Verbal noun of → brecciate.

nasim (#)

Fr.: brise   

A wind or current of air, especially a light or moderate one (2-14 m/sec).

From O.Sp. briza "cold northeast wind;" alternatively from East Frisian brisen "to blow fresh and strong."

Nasim "gentle breeze," from Ar.

Breit-Wheeler process
  فراروند ِ برایت-ویلر   
farâravand-e Breit-Wheeler

Fr.: processus Breit-Wheeler   

The production of an → electron-positron pair in the → collision of two → gamma ray → photons (γγ → e+e-). It is the → inverse process of → Dirac annihilation (e+e-→ γγ). The Breit-Wheeler process is the simplest way by which pure → light can be potentially transformed into → matter. However, as of 2014, this process has never been observed in practice because of the difficulty in preparing colliding → gamma ray beams.

Breit, G. & Wheeler, J. A. 1934, Collision of two light quanta. Phys. Rev. 46, 1087; → process.


Fr.: rayonnement de freinage, bremsstrahlung   

The → electromagnetic radiation emitted by a → fast moving → charged particle when it passes within the strong → electric field of an → atomic nucleus and is → decelerated.

Bremsstrahlung, from Ger. Bremse "brake" + Strahlung "radiation," from strahlen "to radiate," from Strahl "ray," from O.H.G. strala "arrow, stripe;" PIE *ster- "to spread."

Legâm-tâbeš, from legâm, → brake, + tâbeš, → radiation.

Brewster angle
  زاویه‌ی ِ بروستر   
zâviye-ye Brewster (#)

Fr.: angle de Brewster   

The → angle of incidence for which the sum of the incident angle and the → angle of refraction is 90°. The value of Brewster's angle for glass is 57° and for water is 53°. Same as → polarizing angle.

Brewster's law; → angle.

Brewster point
  نقطه‌ی ِ بروستر   
noqte-ye Brewster

Fr.: point de Brewster   

A → neutral point located 15 to 20° directly below the Sun.

Brewster's law; → point

Brewster's law
  قانون ِ بروستر   
qânun-e Brewster

Fr.: loi de Brewster   

The amount of the polarization of light reflected from a surface is a maximum when the reflected ray is at right angles to the refracted ray. See also → polarizing angle.

Named after Sir David Brewster (1781-1868), Scottish physicist; → law.

pol (#)

Fr.: pont   

1) An apparent structure of → gas or → stars linking one → galaxy to another, such as → Magellanic Bridge.
2) Any one of a variety of → elctrical networks in which one branch connects two points of equal → potential and so carries no → current when the → circuit is suitably adjusted.
3) In → graph theory, a simple → edge whose removal disconnects a → graph.

M.E. brigge, O.E. brycge, from P.Gmc. *brugjo (cf. Ger. Brücke), from PIE *bhru- "log, beam."

Pol, Mid.Pers. puhl,, Av. pərətav- "bridge, passage."

  درخشان، روشن   
deraxšân, rowšan

Fr.: brillant   

Giving out or reflecting much light, shining.

O.E. bryht, from beorht "bright, splendid," from P.Gmc. *berkhiaz, from PIE base *bhereg- "to gleam, white" (cf. Av. brāz- "to shine, gleam, flash, radiate," Skt. bhrajate "shines, glitters," Mod.Pers. balk, warq, barx, barq "flash, flame, light," barâz "beauty, grace, elegance," barâzidan "to render good, beautiful," Lith. breksta "to dawn," Welsh berth "bright, beautiful," L. flagrare "to blaze"). → electricity.

Deraxšân and rowšan both from M.P. rôc, O.Pers. raucah-, Av. raocah- "light, luminous; daylight;" cf. Skt roka- "brightness, light", cognate with Gk. leukos "white, clear", L. lux "light" (also lumen, luna), PIE *leuk- "light, brightness". The Mod.Pers. words ruz "day," foruq "light", and afruxtan "to light, kindle" also belong to this family, as well as the E. light, Ger. Licht, and Fr. lumière.

bright giant
  غول ِ تابناک   
qul-e tâbnâk

Fr.: géante lumineuse   

An → evolved star which is more → luminous than normal → giant stars (→ luminosity class III) and between ordinary giants and → supergiants (class I). It is denoted by the symbol II. Examples are → Canopus and → Adhara.

bright; → giant.

bright nebula
  میغ ِ روشن، ~ درخشان   
miq-e rowšan, ~ deraxšân

Fr.: nébuleuse brillante   

In contrast to a → dark nebula, a bright cloud of interstellar gas and dust. The term designates both emission nebulae and reflection nebulae.

bright; → nebula.


Fr.: embrillancement   

The act or process of becoming bright or brighter. → limb brightening, → gravity brightening

Verbal noun of brighten, from → bright.

deraxšandegi (#)

Fr.: brillance   

General:The state or quality of being bright.
Astronomy:The amount of light or other radiation received from a celestial object. It depends on the intrinsic brightness of the object, its distance and the amount of interstellar extinction. → luminosity.

bright + → -ness.

Deraxšandegi, from deraxš, present stem of deraxšidan "to shine," → bright, + -andé adjective suffix + -gi noun suffix.

brightness distribution
  واباژش ِ درخشندگی   
vâbâžeš-e deraxšandegi

Fr.: distribution de brillance   

A statistical distribution of the brightness of an astronomical extended object.

brightness; → distribution.

Vâbâžeš, → distribution; deraxšandegi, → brightness.

<< < B r bac Bal Bar bar bea beh Bes bia Big bin bin bip Bla bla bli blu Boh Bon Bot bow bre bri bro bur > >>