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: 13116 Search : far
Bragg's law
  قانون ِ براگ   
qânun-e Bragg

Fr.: loi de Bragg   

A parallel beam of monochromatic X-rays of wavelength λ, incident on a given set of parallel crystal planes at a grazing angle θ will give rise to a reflected beam whenever: n λ = 2d . sinθ, where n is an integer representing the difference in path length, and d is the perpendicular distance between a pair of adjacent planes.

Named after William Lawrence Bragg (1890-1971), British physicist, who, in collaboration with his father, William Henry Bragg (1862-1942), joint Nobel Prize in Physics 1915, pioneered X-ray analysis and spectrometry; → law.

brake
  ۱) لگام، ترمز؛ ۲) لگامیدن، ترمز کردن   
1) legâm, tormoz 2) legâmidan, tormoz kardan

Fr.: 1) frein; 2) freiner   

1) A device for slowing or stopping a vehicle or other moving mechanism by the absorption or transfer of the energy of momentum, usually by means of friction.
2) To slow or stop by means of or as if by means of a brake (Dictionary.com).

From O.Du. braeke "flax brake," from breken "to break."

Legâm originally "a horse bit," on the model of Fr. frein "horse bit; motor brake;" and Ger. Bremse "horse bit; brake;" tormoz, loan from Russ. тормоз.

braking
  لگامش   
legâmeš

Fr.: freinage   

The act or fact of stopping by means of or as if by means of a brake. See: → magnetic braking; → radiative braking; → tidal braking; → braking index.

Verbal noun of → brake.

braking index
  دیشن ِ لگامش   
dišan-e legâmeš

Fr.: indice de freinage   

A parameter indicating the rate at which a → pulsar slows down. Neutron stars are powered by → rotational energy and lose energy by accelerating particle → winds and by emitting → electromagnetic radiation. The → rotation frequency, Ω, thus decreases with time and this slowdown is usually described by the relation Ω. = - kΩn, where k is a positive constant which depends on the → moment of inertia and the → magnetic dipole moment of the → neutron star and n is the braking index. Conventionally, the braking index is derived by differentiation of the above equation, yielding n = ΩΩ.. / Ω.2. In a highly simplified model in which the spin-down torque arises from dipole radiation at the rotation frequency, one expects n = 3 (Johnston, S., Galloway, D., 1999, arXiv:astro-ph/9905058).

braking; → index.

branch
  ۱) شاخه؛ ۲) شاخه زدن   
1) šâxé (#); 2) šâxé zadan (#)

Fr.: 1) branche; 2) se ramifier   

1a) General: A shoot or arm-like limb of a tree; anything like a limb of a tree; any offshoot from a main trunk.
1b) Astro.:asymptotic giant branch; → blue horizontal-branch stars; → red giant branch; → branching; → branching ratio.
1c) Math.: Any of the two halves of a → hyperbola.
1d) Math.: A section of a curve separated by → discontinuity from the rest of the curve.
2a) To put forth branches.
2b) To spread in branches.

M.E., from O.Fr. branche, from L.L. branca "a claw, paw."

1) Šâxé "branch," from Mid.Pers šâk, cf. Mod.Pers. šâx, šax "branch; horn," Skt. sakha- "a branch, a limb," Arm. cax, Lit. šaka, O.S. soxa, PIE *kakhâ "branch."
2) Šâxé zadan with verb zadan "to strike, beat," → outcrop.

branching
  شاخه‌زد   
šâxé-zad

Fr.: branchement   

The act of dividing into branches. → branching ratio.

branch; → -ing.

branching ratio
  وابر ِ شاخه‌زد   
vâbar-e šâxé-zad

Fr.: rapport de branchement   

A quantity used to describe a → radionuclide that has more than one → decay mode. For a particular decay mode, the ratio of the number of atoms decaying by that decay mode to the number decaying in total: BRi = ki/(k1 + k2 + ...) = ki/k, where k is → decay constant.

branching; → ratio.

brane
  برین   
breyn (#)

Fr.: brane   

In theoretical physics, an entity which can have any number of allowed spatial dimensions. It is usually accompanied by a prefix, i.e. p-brane, indicating the number of dimensions. For example, a 0-brane is a zero-dimensional point-like particle, a 1-brane is a → string, a 2-brane is a "membrane," and so forth. Our Universe is a 3-brane.

Brane, short for membrane, from L. membrana "parchment," from membrum "limb, member of the body," → member.

Breyn, loanword from E., as above.

break
  ۱) شکستن؛ بریدن؛ گسستن؛ ۲) شکست؛ برش؛ بره؛ گسست   
1) šekastan; boridan; gosastan; 2) šekast; boreš, boré; gosast

Fr.: 1) couper, rompre; 2) brisure, coupure   

1) To separate into parts or fragments violently; to become broken.
2) The act or instance of breaking; fracture, rupture; a sudden decline in a continuity.

From break, from M.E. breken, O.E. brecan, from P.Gmc. *brekan (cf. Du. breken, O.H.G. brehhan, Ger. brechen), from PIE base *bhreg- "to break" (see also → fraction).

1) Šekastan, škan- "to break, split;" Mid.Pers. škastan "to break;" Av. scind-, scand "to break, cleave;" Proto-Iranian *skand- "to break, cleave;" PIE sken- "to cut off."
Boridan "to cut off," → cut.
Gosastan "to tear, cut, break," from Mid.Pers. wisistan "to break, split;" Av. saed-, sid- "to split, break," asista- "unsplit, unharmed;" cf. Skt. chid- "to split, break, cut off;" Gk. skhizein "to split;" L. scindere "to split;" Goth. skaidan; O.E. sceadan "to divide, separate;" PIE base *skei- "to cut, split."
2) Šekast; boreš boré; gosast, respective nouns from the verbs.

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.

breakthrough
  تراشکافت   
tarâšekâft

Fr.: percée   

1) An act of overcoming or penetrating an obstacle or restriction.
2) A military offensive that penetrates an enemy's lines of defense.
3) A major achievement or success that permits further progress, as in technology (TheFreeDictionary.com).

break; → through.

Tarâšekâft, from tarâ-, → trans-, + šekâft, past stem of šekâftan "to split, break, tear," → fission.

breccia
  برش   
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.

brecciate
  برشیدن   
berešidan

Fr.: bréchifier   

To form as → breccia.

From → breccia + → -ate.

brecciated
  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.

brecciation
  برشش   
berešeš

Fr.: bréchification   

The formation of → breccia.

Verbal noun of → brecciate.

breeze
  نسیم   
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.

bremsstrahlung
  لگام-تابش   
legâm-tâbeš

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.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc coh col col col Com com com com com com com com Com con 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 Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>