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: 479
bolometer
  تاوسنج   
tâvsanj

Fr.: bolomètre   

1) An instrument for measuring the intensity of radiant energy in amounts as small as one millionth of an erg. It uses the change in resistance of a thin conductor caused by the heating effect of the radiation. → actinometer, → photometer, → pyrheliometer, → pyrometer, radiometer.
2) In astronomy, an instrument that measures the amount of radiant energy received from a celestial object.

From Gk. bole "stroke, beam of light," from ballein "to throw" + middle suffix -o- + → -meter..

Tâvsanj, from tâv "light, brightness, heat, warmth" (from tâbidan "to radiate") + sanj, → -meter.

bolometric
  تاوسنجی، تاوسنجیک   
tâvsanji, tâvsanjik

Fr.: bolométrique   

Of or relating to or measured by a → bolometer.

bolometer; → -ic.

bolometric correction
  ارشایش ِ تاوسنجی، ~ تاوسنجیک   
aršâyeš-e tâvsanji, ~ tâvsanjik

Fr.: correction bolométrique   

The difference between the → visual magnitude and → bolometric magnitude.

bolometric; → correction.

bolometric luminosity
  تابندگی ِ تاوسنجی، ~ تاوسنجیک   
tâbandegi-ye tâvsanji, ~ tâvsanjik

Fr.: luminosité bolométrique   

The total rate of energy output of an object integrated over all wavelengths.

bolometric; → luminosity.

bolometric magnitude
  برز ِ تاوسنجی، ~ تاوسنجیک   
borz-e tâvsanji, ~ tâvsanjik

Fr.: magnitude bolométrique   

The magnitude of an astronomical object for the entire range of its electromagnetic spectrum.

bolometric; → magnitude.

Boltzmann constant
  پایای ِ بولتسمن   
pâyâ-ye Boltzmann

Fr.: constante de Boltzmann   

Boltzmann's constant.

Boltzmann's constant.

Boltzmann factor
  کروند ِ بولتسمن   
karvand-e Boltzmannn

Fr.: facteur de Boltzmann   

The factor e-E/kT involved in the probability for atoms having an excitation energy E and temperature T, where k is Boltzmann's constant.

Boltzmann's constant; → factor.

Boltzmann's constant
  پایای ِ بولتسمن   
pâyâ-ye Boltzmann

Fr.: constante de Boltzmann   

The physical constant, noted by k, relating the mean → kinetic energy of → molecules in an → ideal gas to their → absolute temperature. It is given by the ratio of the → gas constant to → Avogadro's number. Its value is about 1.380 x 10-16erg K-1.

Named after the Austrian physicist Ludwig Boltzmann (1844-1906), who made important contributions to the theory of statistical mechanics; → constant.

Boltzmann's entropy formula
  دیسول ِ درگاشت ِ بولتسمن   
disul-e dargâšt-e Boltzmann

Fr.: formule d'entropie de Boltzmann   

In → statistical thermodynamics, a probability equation relating the → entropy S of an → ideal gas to the quantity Ω, which is the number of → microstates corresponding to a given → macrostate: S = k. ln Ω. Same as → Boltzmann's relation.

Boltzmann's constant; → entropy; → formula.

Boltzmann's equation
  هموگش ِ بولتسمن   
hamugeš-e Boltzmann

Fr.: équation de Boltzmann   

1) An equation that expresses the relative number (per unit volume) of → excited atoms in different states as a function of the temperature for a gas in → thermal equilibrium: Nu/Nl = (gu/gl) exp (-ΔE/kTex), where Nu and Nl are the upper level and lower level populations respectively, gu and gl the → statistical weights, ΔE = hν the energy difference between the states, k is → Boltzmann's constant, and h  → Planck's constant.

Boltzmann's constant; → equation.

Boltzmann's relation
  باز‌آنش ِ بولتسمن   
bâzâneš-e Boltzmann

Fr.: relation de Boltzmann   

A relation between the → entropy of a given → state of a → thermodynamic system and the → probability of the state: S = k . ln Ω where S is the entropy of the system, k is → Boltzmann's constant, and Ω the thermodynamic probability of the state. Boltzmann's relation connects → statistical mechanics and → thermodynamics. Ω is the number of possible → microstates of the system, and it represents the → randomness of the system. The relation also describes the statistical meaning of the → second law of thermodynamics. This expression has been carved above Boltzmann's name on his tombstone in Zentralfreihof in Vienna. Same as → Boltzmann's entropy formula.

Boltzmann's constant; → relation.

bond
  بند   
band (#)

Fr.: lien   

The attractive force that holds together neighboring atoms in molecules.

Bond, variant of band, from M.E. bende, O.E. bend, from O.Fr. bande, bende, PIE *bendh- "to bind" (cf. Goth bandi "that which binds;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," bandhah "a tying, bandage").

Band "band, tie," from Mid.Pers., O.Pers./Av. band- "to bind," banda- "band, tie."

Bond albedo
  سپیدای ِ باند   
sepidâ-ye Bond

Fr.: albedo de Bond   

The fraction of the total amount of electromagnetic radiation falling upon a non-luminous spherical body that is reflected in all directions by that body. The bond albedo takes into account all wavelengths at all → phase angles. Compare with → geometric albedo.

Named after the American astronomer George Phillips Bond (1825-1865), who proposed it; → albedo.

Bondi-Hoyle accretion
  فربال ِ بوندی-هویل   
farbâl-e Bondi-Hoyle

Fr.: accrétion de Bondi-Hoyle   

The → accretion of mass by a star (assumed as point particle) moving at a steady speed through an infinite, uniform gas cloud. It is directly proportional to the star mass (M) and the medium density (ρ) and inversely proportional to the relative star/gas velocity (v). In its classical expression: 4πρ(G M)2 / v3, where G is the → gravitational constant. See Bondi & Hoyle (1944, MNRAS 104, 273) and Bondi (1952, MNRAS 112, 195). For a recent treatment of accretion in a turbulent medium see Krumholtz et al. 2006 (ApJ 638, 369).

Named after Hermann Bondi (1919-2005), an Anglo-Austrian mathematician and cosmologist and Fred Hoyle (1915-2001), British mathematician and astronomer best known as the foremost proponent and defender of the steady-state theory of the universe; → accretion.

Bondi-Hoyle accretion radius
  شعاع ِ فربال ِ بوندی-هویل   
šo'â'-e farbâl-e Bondi-Hoyle

Fr.: rayon de l'accrétion de Bondi-Hoyle   

In the → Bondi-Hoyle accretion process, the radius where the gravitational energy owing to star is larger than the kinetic energy and, therefore, at which material is bound to star. The Bondi-Hoyle accretion radius is given by RBH = 2 GM / (v2 + cs2) where G is the gravitational constant, M is the stellar mass, v the gas/star relative velocity, and cs is the sound speed.

Bondi-Hoyle accretion; → radius.

Bonner Durchmusterung (BD)
     
Bonner Durchmusterung

Fr.: Bonner Durchmusterung   

A catalog of 324,188 stars in the → declination zones +89 to -01 degrees. The goal of the survey was to obtain a → position and estimated → visual magnitude for every star visible with the 78 mm → refracting telescope at Bonn. Actual → magnitude estimates were made and reported to 0.1 mag for all stars down to 9.5 mag. Positions are given to the nearest 0.1 sec in → right ascension and 0.1 arcmin in declination. The survey was carried out by Friedrich W. Argelander (1799-1875) and his assistants in the years 1852-1861.

The Ger. name means Bonn Survey.

Bonnor-Ebert mass
  جرم ِ بونور-ابرت   
jerm-e Bonnor-Ebert

Fr.: masse de Bonnor-Ebert   

The largest gravitationally stable mass of the → Bonnor-Ebert sphere.

After W.B. Bonnor (1956) and R. Ebert (1955); → mass.

Bonnor-Ebert sphere
  سپهر ِ بونور-ابرت، کره‌ی ِ ~   
epehr-e Bonnor-Ebert, kore-ye ~

Fr.: sphère de Bonnor-Ebert   

A sphere of interstellar gas at uniform temperature in equilibrium under its own gravitation and an external pressure. The pressure of a hotter surrounding medium causes the sphere to collapse. → Bonnor-Ebert mass.

Bonnor-Ebert mass; → sphere.

book
  کتاب، نامه، نسک   
ketâb (#), nâmé (#), nask (#)

Fr.: livre   

A bound set of printed or manuscript pages.

M.E., from O.E. boc "book, written document;" cf. Ger. Buch "book;" Du. boek; O.N. bôk; Gothic boka.

Ketâb, loanword from Ar.
Nâmé "book, letter;" Mid.Pers. nâmag "book, letter, inscription;" O.Pers./Av. nāman- "name;" cf. Skt. nama-; Gk. onoma, onuma; L. nomen; PIE *nomen-.
Nask; Mid.Pers. nask "one of the book comprising Avesta;" Av. naska-, literally "bundle, bunch," naskô.frasa- "one who devotes himself to the study of nasks;" cf. Skt. nah- "to tie, bind," nahyati "he ties, binds;" L. nectere "to tie, bind," nodus "node;" O.Ir. nasc "a tie, bond, ring," nascim "I bind."

Boolean
  بولی   
Booli (#)

Fr.: de Boole   

A → variable or → function which takes the value → true or → false. → Boolean algebra.

After the English mathematician George Boole (1815-1864), the founder of mathematical, or symbolic, logic.

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