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: 13176 Search : in
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.

baryon-photon ratio
  وابر ِ باریون-فوتون   
vâbar-e bâriyon-foton

Fr.: rapport baryon-photon   

The → baryon number compared with the number of photons in the → Universe. The baryon-photon ratio can be estimated in a simple way. The → energy density associated with → blackbody radiation of → temperature  T is aT4, and the mean energy per photon is ~kT. Therefore, the number density of blackbody photons for T = 2.7 K is: nγ = aT4/kT = 3.7 x 102 photons cm-3, where a = 7.6 x 10-15 erg cm-3 K-4 (→ radiation density constant) and k = 1.38 x 10-16 erg K-1 (→ Boltzmann's constant). The number density of baryons can be expressed by ρm/mp, where ρm is the mass density of the Universe and mp is the mass of the → proton (1.66 x 10-24 g). → CMB measurements show that the baryonic mean density is ρm = 4.2 x 10-31 g cm-3 (roughly 5% of the → critical density). This leads to the value of ~ 2 x 10-7 for the number density of baryons. Thus, the baryon/photon ratio is approximately equal to η = nb/nγ = 2 x 10-7/3.7 x 102 ~ 5 x 10-10. In other words, for each baryon in the Universe there is 1010 photons. This estimate is in agreement with the precise value of the baryon-photon ratio 6.14 x 10-10 derived with the → WMAP. Since the photon number and the baryon number are conserved, the baryon-photon ratio stays constant as the Universe expands.

baryon; → photon; → ratio.

baryonic dark matter
  ماده‌ی ِ سیاه ِ باریونی   
mâde-ye siyâh-e bâriyoni

Fr.: matière noire baryonique   

Dark matter made up of → baryons that are not luminous enough to produce any detectable radiation. It is generally believed that most dark matter is → non-baryonic. The baryonic dark matter could reside in a number of forms, including cold gas and compact objects.

baryonic; → dark; → matter.

baryonic matter
  ماده‌ی ِ باریونی   
mâde-ye bâriyoni (#)

Fr.: matière baryonique   

Ordinary matter composed of → baryons, i.e. → protons and → neutrons, as distinct from → non-baryonic, exotic forms.

Adj. of → baryon; → matter.

basalt
  بازالت   
bâzâlt (#)

Fr.: basalte   

A dark fine-grained → igneous rock typically composed of → plagioclase with → pyroxene and → olivine and often displaying a columnar structure.

From L.L. basaltes, misspelling of L. basanites "very hard stone," from Gk. basanites, from basanos "touchstone," from Egyptian baban "a stone used by the Egyptians as a touchstone of gold."

base
  ۱، ۲، ۳، ۴) پایه، ۵) پایگاه، ۶) باز   
1, 2, 3, 4) pâyé (#), 5) pâygâh (#), 6) bâz (#)

Fr.: base   

1) The bottom support of anything; a fundamental principle or groundwork.
2) Geometry: The line or surface on which a figure is assumed to stand.
3) Arithmetic: The number which, raised to various powers, forms the main counting units of a system. Thus 10 is the base of the decimal system.
4) Logarithm: The number a in the equation N = ax. The base of common logarithm is 10.
5) A centre of operations or supply, such as a → database.
6) Chemistry: A substance that reacts with an acid to yield a salt and water.

M.E., from O.Fr. bas, from L. basis "foundation," from Gk. basis "step, pedestal," from bainein "to step."

Pâyé "base," from pâ, pây "foot," from Mid.Pers. pâd, pây; Av. pad-, cf. Skt. pat: Gk. pos, genitive podos; L. pes; PIE *pod-/*ped-.
Pâygâh, from pâyé + gâh "place" (O.Pers. gāθu-; Av. gātav-, gātu- "place, throne, spot;" cf. Skt. gâtu- "going, motion; free space for moving; place of abode;" PIE *gwem- "to go, come."
Bâz, loan from Fr., as above.

baseline
  پایه-خط   
pâye-xatt

Fr.: ligne de base   

1) In radio interferometry, the separation between the electrical, or phase centers of two interferometer elements.
2) In spectroscopy, the contribution to a spectrum from phenomena that are not of astronomical interest, such as frequency dependent properties of the receivers, or by astronomical sources other than those under study.

base; → line.

basic
  بازی   
bâzi (#)

Fr.: basique   

Chemistry: Of or denoting or of the nature of or containing a → base. Same as → alkaline.

base; → -ic.

basin
  حوضه   
howzé (#)

Fr.: bassin   

A large impact crater on a planet or moon, typically several hundred kilometers across, flooded with basaltic lava and surrounded by concentric rings of faulted cliffs.

From O.Fr. bacin, from V.L. *baccinum, from L. bacca "water vessel," perhaps originally Gaulish.

Howzé, from howz "pond, a large reservoir of water" (from Ar. hauz) + noun suffix.

<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB 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 coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl 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 inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai 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 rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl 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 > >>