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: 13048 Search : far
Bekenstein formula
  دیسول ِ بکنشتاین   
disul-e Bekenstein

Fr.: formule de Bekenstein   

The mathematical expression giving the → entropy, S, of a → black hole as a function of the area of its → event horizon, A: S = (kc3A)/(4Għ), where k is → Boltzmann's constant, ħ is the → reduced Planck's constant, and G the → gravitational constant. It can also be expressed by S = (kA)/(4lP2), where lP is the → Planck length. The existence of this entropy led to the prediction of the → Hawking radiation, because an entropy is associated with a temperature and a temperature to a → thermal radiation. The entropy of a black hole increases continuously because the fall of material into it increases its area.

For Jacob D. Bekenstein (1947-), an Israeli theoretical physicist, who contributed to the foundation of black hole thermodynamics; → formula.

bel (B)
  بل   
bel (#)

Fr.: bel   

A dimensionless unit to measure sound. One bel designates a ratio 10:1 between two quantities, P1 and P0, which have the dimension of a power: n [B] = log (P1/P0), in Bel units, with → natural logarithm. If one sound is 2 bels louder than another, this means the louder sound is 100 times more intense than the fainter one. It is also common to use this definition for quantities that are proportional to a power, such as energy, work, intensity, or voltage. The bel was too large for everyday use, so the → decibel (dB), equal to 0.1 bel, is more commonly used.

This unit was put forward by engineers of the Bell telephone network in 1923 and named in honor of the inventor of the telephone, Alexander Graham Bell (1847-1922), who also invented techniques for teaching speech to the deaf.

Belinda (Uranus XIV)
  بلیندا   
Belindâ

Fr.: Belinda   

One of the small satellites of → Uranus discovered from the Voyager 2 photographs taken during its encounter with the planet in 1986.

Named after the heroine in Alexander Pope's The Rape of the Lock.

Bell's inequality
  ناهموگی ِ بل   
nâhamugi-ye Bell

Fr.: inégalité de Bell   

Any of a large number of inequality relations developed to study the → hidden variable hypothesis suggested in the → EPR paradox. Using Bell's inequalities, the → Aspect experiment showed that no local hidden variable theory can make predictions in agreement with those of quantum mechanics. If, in a measurement, the inequality is violated, the measurement is in agreement with the predictions of the quantum theory. If the equality is satisfied, it suggests that a classical, causal, and local model is adequate to explain the outcome of the measurements. See also → quantum entanglement.

John Stewart Bell (1928-1990); → inequality.

Bellatrix (γ Orionis)
  بلاتریکس، مرزم   
Bellatriks, Merzam

Fr.: Bellatrix   

A bright, blue → giant star ( → spectral type B2 III), one of the main stars of the constellation → Orion. With a visual magnitude of 1.64, it is about 1000 times more luminous than the Sun, and lies at a distance of 243 → light-years.

From L. bellatrix "a female warrior," fem. of bellator, from bellum "war."

Merzam, Ar. name of the star; its other name is Nâjed.

belong
  پرگتیدن، پرگت داشتن   
pargetidan, parget dâštan

Fr.: appartenir   

1) (with preposition to) To be the property of.
2) (with preposition to) To be a part or adjunct of.

M.E. belongen, from be- intensive prefix, + longen "to go," from O.E. langian "pertain to, to go along with;" akin to Du. belangen, Ger. belangen; of unknown origin.

Pargetidan, literally "to surround, to relate with" (on the model of L. pertinere "pertain," Skt. parigraha- "surrounding; relation to"), from parget "to hold, seize, take around," from par- "around," → peri-, + get "to take, sieze," as in Tâleši gate "to take," Târi gata, Sorxeyi, Lâsgardi, Semnâni, Šâhmerzâdi -git- "take, seize," variants of gereftan "take, hold," → concept.

belongs to
  می‌پرگتد، پرگت دارد   
mipargetad, parget dârad

Fr.: appartient   

If x is an → element of a → set S, then x belongs to S and this is written x ∈ S.

Third person present verb of → belong.

belt
  کمربند   
kamarband (#)

Fr.: ceinture   

A strip of leather or cloth worn around the waist. Something that resembles this type of band, e.g. → Gould's Belt, → Belt of Venus.

O.E. belt, from P.Gmc. *baltjaz, from L. balteus "girdle;" → Orion.

Kamarband "belt," from kamar "waist" (Mid.Pers. kamar "waist; belt, girdle," Av. kamarâ- "belt") + band "a band, tie, belt."

Belt of Orion
  کمربند ِ شکارگر، ~ اریون   
kamarband-e Šekârgar, ~ Oryon

Fr.: Baudrier d'Orion   

Orion's Belt.

belt; → Orion.

Belt of Venus
  کمربند ِ ناهید   
kamarband-e Nâhid

Fr.: Ceinture de Vénus   

A pink to brownish border above the horizon separating the Earth's dark shadow on the sky from the sky above it. The Belt of Venus appears during a cloudless twilight just before sunrise or after sunset. It is due to scattered red sunlight in the atmosphere. Also called anti-twilight arc.

belt, → Venus.

BepiColombo
     
BepiColombo

Fr.: BepiColombo   

A → European Space Agency (ESA) mission aimed at studying → Mercury, the least explored planet in the inner → Solar System. It was launched on 20 October 2018. Among several goals, BepiColombo will make a complete map of Mercury at different wavelengths. It will chart the planet's → mineralogy and elemental → composition, determine whether the interior of the planet is molten or not, and investigate the extent and origin of Mercury's → magnetic field, the properties of its → magnetosphere, and history of the planet. The trajectory will also be modified by eight planetary flybys: of Earth in April 2020, Venus in 2020 and 2021, and then six times of Mercury itself between 2021 and 2025. BepiColombo will enter Mercury orbit in December 2025. BepiColombo is a joint mission between ESA and the Japanese Aerospace Exploration Agency (JAXA), executed under ESA leadership.

Named after Giuseppe (Bepi) Colombo (1920-1984), a scientist who studied Mercury's orbital motion in detail as well as orbits and interplanetary travel in general.

Berenice's Hair
  گیسو   
Gisu

Fr.: Chevelure de Bérénice   

Coma Berenices.

Bernoulli equation
  هموگش ِ برنویی   
hamugeš-e Bernoulli

Fr.: équation de Bernoulli   

The equation expressing → Bernoulli's theorem: P + (1/2)ρV2 + ρgz = constant, where P is the fluid → pressure, V is → velocity, ρ is → density, g is the acceleration due to → gravity, and z is the vertical reference → level. The theree terms are called → static pressure, → dynamic pressure, and → hydrostatic pressure, respectively. The Bernoulli equation states that the total pressure along a → streamline is → constant.

Bernoulli's theorem; → equation.

Bernoulli's theorem
  فربین ِ برنویی   
farbin-e Bernoulli

Fr.: théorème de Bernoulli   

A statement of the → conservation of energy in the → steady flow of an → incompressible, → inviscid fluid. Accordingly, the quantity (P/ρ) + gz + (V2/2) is → constant along any → streamline, where P is the fluid → pressure, V is the fluid → velocity, ρ is the mass → density of the fluid, g is the acceleration due to → gravity, and z is the vertical → height. This equation affirms that if the internal velocity of the flow goes up, the internal pressure must drop. Therefore, the flow becomes more constricted if the velocity field within it increases. Same as the → Bernoulli equation.

After Daniel Bernoulli (1700-1782), the Swiss physicist and mathematician who put forward the theorem in his book Hydrodynamica in 1738; → theorem.

berry
  پلار   
pelâr

Fr.: baie   

1) A small, round fruit on particular plants and trees.
2) Botany: Any of various small edible fruits such as the raspberry, blackberry, and strawberry.

M.E. berye, from O.E. berie "berry, grape," cf. M.Du. bere, Ger. Beere, O.Sax. winberi, Gothic weinabasi "grape," Norwegian and Danish bær, of unknown origin.

Pelâr, from Hamadâni, Malâyeri pellâr, pellâra "berry, grape berry;" cf. Laki, Xonsâri palâra "raisin grape," Aligudarzi pellâr "part of a raison grape," of unknown origin (related to berry, as above?).

beryllium
  بریلیوم   
beriliom (#)

Fr.: béryllium   

A grey, very hard metallic chemical element; symbol Be. → Atomic number 4; → atomic weight 9.01218; → melting point about 1,278°C; → boiling point 2,970°C (estimated); → specific gravity 1.85 at 20°C; → valence +2. Beryllium occurs as beryl, from which it is obtained by electrolysis. Used for light alloys which are corrosion resistant. Beryllium was discovered by Louis Nicolas Vauquelin (1763-1829) in 1798. First isolated by Friedrich Wöhler (1800-1882) in 1828.

From L. beryll(us), from beryl, a mineral, beryllium aluminum silicate, Be3Al2Si6O18, M.E. beril, from O.Fr., from L. berillus, from Gk. beryllos, + → -ium.

Bessel
  بسل   
Besel

Fr.: Bessel   

From Friedrich Wilhelm Bessel (1784-1846), German astronomer and mathematicians, who made fundamental contributions to positional and spherical astronomy.

Bessel equation
  هموگش ِ بسل   
hamugeš-e Besel

Fr.: équation de Bessel   

A linear second-order differential equation, the solutions to which are called Bessel functions.

From → Bessel; → equation

Hamugeš, → equation.

Bessel's star
  ستاره‌ی ِ بسل   
setâre-ye Bessel

Fr.: étoile de Bessel   

Same as → 61 Cygni, the first star whose distance was measured, by Friedrich Bessel in 1838.

Bessel; → star.

Besselian
  بسلی   
Besseli

Fr.: besselien, de Bessel   

Of or pertaining to Friedrich Wilhelm Bessel (1784-1846) or to his discoveries. → Besselian day number Bessel equation Besselian star constant Besselian year.

Bessel.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit 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 con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>