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
barometric law
  قانون ِ فشارسنجی، ~ فشارسنجیک   
qânun-e fešârsanji, ~ fešârsanjik

Fr.: loi barométrique   

The atmospheric pressure decreases exponentially from any reference surface as the altitude increases.

barometer; → law.

Qânun, → law, fešârsanji, fešârsanjik "barometric," from fešârsanj, → barometer.

barotropic
  فشارگرد   
fešârgard

Fr.: barotrope   

In a fluid, conditions where surfaces of constant pressure are parallel to surfaces of constant temperature. This state is equivalent to zero → baroclinicity.

baro-; → -tropic.

barotropic gas
  گاز ِ فشارگرد   
gâz-e fešârgard

Fr.: gaz barotrope   

A gas whose density is a function solely of pressure.

barotropic; → gas.

barotropic instability
  ناپایداری ِ فشارگرد   
nâpâydâri-ye fešârgard

Fr.: instabilité barotrope   

A hydrodynamical instability that arises when the horizontal → shear gradient becomes very large. Barotropic instabilities grow by extracting kinetic energy from the mean flow field.

barotropic; → instability.

barotropy
  فشارگردی   
fešârgardi

Fr.: barotropie   

A state of a fluid in which the surfaces of constant density coincide with surfaces of constant pressure (isobaric).

barotropic gas.

barred
  میله‌دار، میله‌ای   
miledâr, milei

Fr.: barré   

Having a bar like structure.

bar.

barred Magellanic spiral
  مارپیچ ِ میله‌دار ِ ماژلانی   
mârpic-e mile-dâr-e Mâželâni

Fr.: spirtale barée magellanique   

A transitional class of object between the classic spiral galaxies and true irregular systems. The → Large Magellanic Cloud, the nearest and best studied example of the class, is, contrary to popular opinion, not an irregular galaxy. The LMC and other members of the SBm class have definite structural signatures. They are generally dominated by a pronounced asymmetric bar -- one that is offset from the optical center of the galaxy -- with a nascent spiral arm emanating from one end. As is the case with irregular galaxies, the optical centers of SBm type systems are not particularly special places. Disk systems later than Sc characteristically lack a central stellar concentration in addition to having weak spiral structure; this is true of SBm-type galaxies. SBm galaxies are typically very active in their star formation activity, often containing a large star-forming complex situated at one end of the bar. Beyond these general trends there is a tremendous amount of dispersion in physical properties within the SBm class, particularly in the strength of the spiral structure. At one extreme are the "one-armed" spirals such as NGC 3664 and NGC 4027 which are dominated by single, looping spiral arm. On the other hand NGC 4861 shows little evidence of spiral structure and it is dominated by a large star-forming complex at one end of its bar. The class smoothly leads to the Barred Magellanic irregulars (IBm) which show no indication of spiral structure (Wilcots et al. 1996, AJ 111, 1575).

Magellanic; → spiral; → galaxy.

barred spiral galaxy
  کهکشان ِ مارپیچ ِ میله‌دار، ~ ~ میله‌ای   
kahkašân-e mârpic-e miledâr

Fr.: galaxie spirale barrée   

A → spiral galaxy that exhibits a bar-shaped structure in its nucleus. → galactic bar.

barred; → spiral; → galaxy.

barrel distortion
  چولگی ِ چلیکی   
cowlegi-ye celiki (#)

Fr.: distortion en barillet   

A defect in an optical system in which magnification decreases with distance from the optical axis, whereby the image of a square appears barrel-shaped. Opposite of → pincushion distortion.

Barrel, M.E. barel, from O.Fr. baril; → distortion.

Cowlegi, → distortion; celiki, relating to celik "barrel".

barrier
  ورغه   
varqé (#)

Fr.: barrière   

General: Anything that prevents passage or blocks.
Physics: 1) A region where the potential energy is greater than the total energy of a particle, whereby the particle cannot go through.
2) The depletion layer of a P-N junction in a diode.

O.F. barrière "obstacle," from V.L. *barraria, from *barra "bar, barrier."

Varqé, from varq "a mound, a dam" + nuance suffix. Varq is probably related to Av. vâra- "barrage," vara- "enclosure," var- "castle," Mid.Pers. var "enclosure," from Av. root var- "to cover, to conceal;" variants: barq (Torbat Heydariyei), valgâ (štiyâni), var (Qomi); cf. Skt. vatra- "a dike, a dam,"varana- "rampart, wall," from vr- "to obstruct, close, cover, hide; to choose."

Barringer Crater
  لاوک ِ برینگر   
lâvak-e Barringer

Fr.: cratère Barringer   

Same as → Meteor Crater.

Names after Daniel Barringer (1860-1929), American geologist, who bought the Crater in 1903, convinced that it was made by a huge → meteorite; → crater.

barycenter
  گرانیگاه   
gerânigâh (#)

Fr.: barycentre   

The center of mass of a system of bodies.

From Gk. barus "heavy," → bar, + → center.

Gerânigâh, from gerâni "weight;" cognate with Gk. barus, → bar, + gâh "place."

Barycentric Coordinate Time (TCB)
  زمان ِ همارا‌ی ِ گرانیگاهی   
zamân-e hamârâ-ye gerânigâhi

Fr.: temps-coordonnée barycentrique (TCB)   

A → coordinate time having its spatial origin at the solar system barycenter. It is intended to be used as the independent variable of time for all calculations pertaining to orbits of planets, asteroids, comets, and interplanetary spacecraft in the solar system. → Barycentric Dynamical Time (IDB).

barycenter; → coordinate; → time.

Barycentric Dynamical Time (TDB)
  زمان ِ توانیک ِ گرانیگاهی   
zamân-e tavânik-e gerânigâhi

Fr.: temps dynamique barycentrique (TDB)   

A time scale previously used in calculations of the orbits of solar system objects (planets, asteroids, comets, and interplanetary spacecrafts). It was based on the Terrestrial Dynamical Time, but took the relativistic effect of time dilation into account to move the origin to the solar system barycenter. It is now superseded by → Barycentric Coordinate Time (TCB).

barycenter; → dynamical; → time.

Barycentric Julian Date (BJD)
  گاهداد ِ ژولی‌ین ِ گرانیگاهی   
gâhdâd-e žulian-e gerânigâhi

Fr.: date julienne barycentrique   

The → Julian Date referenced to the → barycenter of the → solar system. The BJD is more precise than the → Heliocentric Julian Day because the Sun is not stationary. It moves due to the → gravitational attraction of Jupiter and the other planets.

barycentric; → Julian Date.

baryogenesis
  باریونزایی   
bâriyonzâyi

Fr.: baryogénèse   

The hypothetical mechanism of creating the → baryon asymmetry in the → Universe. Universe. Explaining the observed matter asymmetry is an important open question in physical cosmology. → Sakharov conditions.

From baryo-, from → baryon + → -genesis.

baryon
  باریون   
bâriyon (#)

Fr.: baryon   

Any of the class of the heaviest → subatomic particles that includes → protons, → neutrons, as well as a number of short-lived particles whose decay products include protons. Baryons obey the → Fermi-Dirac statistics. They form a subclass of the → hadrons and are further subdivided into → nucleons and → hyperons.

Gk. barys "heavy" + → -on, from "fermion."

baryon acoustic oscillation (BAO)
  نوش ِ صداییک ِ باریونی   
naveš-e sedâyik-e bâryoni

Fr.: oscillation acoustique baryonique   

In cosmology, one of a series of peaks and troughs that are present in the power spectrum of matter fluctuations after the → recombination era, and on large scales. At the time of the Big Bang, and for about 380,000 years afterwards, Universe was ionized and photons and baryons were tightly coupled. Acoustic oscillations arose from perturbations in the primordial plasma due to the competition between gravitational attraction and gas+photons pressure. After the epoch of recombination, these oscillations froze and imprinted their signatures in both the → CMB and matter distribution. In the case of the photons, the acoustic mode history is manifested as the high-contrast Doppler peaks in the temperature anisotropies. As for baryons, they were in a similar state, and when mixed with the non-oscillating → cold dark matter perturbations, they left a small residual imprint in the clustering of matter on very large scales, ~100 h-1Mpc (h being the → Hubble constant in units of 100 km s-1 Mpc-1). The phenomenon of BAOs, recently discovered using the Sloan Digital Sky Survey data, is a confirmation of the current model of cosmology. Like → Type Ia supernovae, BAOs provide a → standard candle for determining cosmic distances. The measurement of BAOs is therefore a powerful new technique for probing how → dark energy has affected the expansion of the Universe (see, e.g., Eisenstein 2005, New Astronomy Reviews 49, 360; Percival et al. 2010, MNRAS 401, 2148).

baryon; → acoustic; → oscillation.

baryon asymmetry
  ناهمامونی ِ باریون   
nâhamâmuni-ye bariyon

Fr.: asymmétrie baryonique   

The observation that in the present → Universe there is → matter but not much → antimatter. Observations do not show the presence of galaxies made of antimatter, nor gamma rays are observed that would be produced if large entities of antimatter would undergo → annihilation with matter. However, the → early Universe could have been baryon symmetric, and for some reason the matter excess has been generated, through some process called → baryogenesis. → Sakharov conditions.

baryon; → asymmetry.

baryon number
  عدد ِ باریونی   
adad-e bâriyoni (#)

Fr.: nombre baryonique   

1) The difference between the total number of → baryons and the total number of → antibaryons in a system of → subatomic particles. It is a measure of → baryon asymmetry and is defined by the quantity η = (nb - nb-)/nγ, called the → baryon-photon ratio, where nb is the → comoving number density of baryons, nb- is the number of antibaryons, and nγ is that of photons. The value of η for the → cosmic microwave background radiation (CMBR) has been very well determined by the → WMAP satellite to be η = (6.14 ± 0.25) x 10-10. The baryon number is assumed to be constant. The photons created in stars amount to only a small fraction, less than 1%, of those in the CMBR.
2) A property of an → elementary particle represented by a → quantum number. It is equal to +1 for a baryon and -1 for an antibaryon. → Bosons, → leptons, and → mesons have a baryon number B = 0. → Quarks and → antiquarks have baryon numbers of B = +1/3 and -1/3, respectively. The baryon number is → conserved in all observed types of particle-particle interaction.

baryon; → number.

<< < -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 > >>