An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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azimuthal angle
  زاویه‌ی ِ سوگانی   
zâviye-ye sugâni

Fr.: angle azimutal   

In → spherical coordinates, an angle measured from the x-axis in the xy-plane.

Azimuthal, adj. from azimuth; → angle.

azimuthal magnetic field
  میدان ِ مغناتیسی ِ سوگانی   
meydân-e meqnâtisi-ye sugâni

Fr.: champ magnétiquue azimutal   

In the → solar dynamo model, a magnetic field that points from east to west or vice-versa.

azimuthal; → magnetic; → field.

azimuthal projection
  فراشانش ِ سوگانی   
farâšâneš-e sugâni

Fr.: projection azimutale   

A map projection on which the → azimuths of all points are shown correctly with respect to the center. A plane tangent to one of the Earth's poles is the basis for polar azimuthal projection.

azimuthal; → projection.

azimuthal quantum number
  عدد ِ کو‌آنتومی ِ سوگانی   
adad-e kuântomi-ye sugâni

Fr.: nombre quantique azimutal   

In quantum mechanics, a quantum number that distinguishes the different shapes of the orbitals.

Azimuthal, adj. from → azimuth; → quantum number.

B ring
  حلقه‌ی ِ B   
halqe-ye B

Fr.: anneau B   

One of → Saturn's rings, lying beyond the → C ring and before the → A ring, extending from 92,000 to 117,300 km (width 25,300 km) from the center of Saturn. The B ring is bounded by the → Huygens Division.

ring.

B star
  ستاره‌یِ B   
setâre-ye B (#)

Fr.: étoile B   

A star of → spectral type B, whose spectrum is marked by absorption lines of hydrogen; also known as B-type star. B-type optical spectra are characterized by the presence of neutral He lines (mainly He I 4471 Å) at about type B9. He I strengthens up to about B2, then decreases. Ionized helium (mainly He II 4541 Å) first appears at about B0. Most metallic lines are absent or weak, except some absorption lines for the higher ionization states of → silicon, → oxygen, → carbon, and → magnesium. These are hot stars with → effective temperatures ranging from about 10,000 K at B9 to nearly 30,000 K at B0. They are between 3 and 20 → solar masses. Some famous examples include: → Rigel, → Achernar, → Hadar.

star.

B-mode polarization
  قطبش ِ ترز ِ B   
qotbeš-e tarz-e B

Fr.: polarisation en mode B   

A → polarization component in the → cosmic microwave background radiation that depends only on → curl, is independent of → gradient, and has → handedness that distinguishes left from right. The B-mode is due to only → vector perturbations or → tensor perturbations. It has two types, the first type, which constitutes the majority of the B-mode polarization, results from → lensing by galaxies that twist the → E-mode polarized light on its journey from the other side of the → observable Universe. The second type can be produced only by → gravitational waves, not by density perturbations. This type of B-mode is incredibly faint, producing temperature variations of about 0.4 microK and accounting for just one part in 10 million in the CMB temperature distribution. It is expected to be generated during cosmic → inflation shortly after the → Big Bang. The → BICEP2 team announced in March 2014 that they had detected the second type of B-modes, consistent with inflation and gravitational waves in the → early Universe. The detected degree scale B-mode polarization has a tensor-to-scalar ratio, r = 0.2 (+0.07, -0.05), which is a measure of the amplitude of the primordial gravitational waves.

B, indicating magnetic-field like; → mode; → polarization.

B-type asteroid
  سیارک ِ گونه‌ی ِ B   
sayyârak-e gune-ye B

Fr.: astéroïde de type B   

A division of → C-type asteroids whose members have relatively low albedos (0.04 to 0.08) and the → ultraviolet absorption below 0.5 μm is small or absent. Examples include → 2 Pallas, 379 Huenna (diameter 62 km), and → 101955 Bennu.

type; → asteroid.

B-type star
  ستاره‌ی ِ گونه‌ی ِ B   
setâre-ye gune-ye B

Fr.: étoile de type B   

Same as → B star.

B, letter of alphabet used in the → Harvard classification; → type; → star.

Baade's window
  روزنه‌ی ِ باده   
rowzane-ye Baade

Fr.: fenêtre de Baade   

An area of the sky with relatively low amounts of  → interstellar dust along the → line of sight, occurring toward the  → constellation of  → Sagittarius, near the → globular cluster NGC 6522. The window, through which stars in the → Galactic bulge are visible, lies 3.9 degrees south of the → Galactic center, corresponding to a line of sight that passes within 1,800 → light-years of the → Milky Way's core. It is named after Walter Baade, who used it to observe → RR Lyrae stars  in the → Galactic bulge region. 

Baade-Wesselink method; → window.

Baade-Wesselink method
  روش ِ باده-وسلینک   
raveš-e Bâdé-Veselink (#)

Fr.: méthode de Baade-Wesselink   

A method used to determine the size of certain types of pulsating stars, including Cepheids, from their magnitude variations (photometry) and the corresponding radial velocities (spectroscopy).

Baade, from Walter (Wilhelm Heinrich) Baade (1893-1960), German/American astronomer, who made important contributions to the research on variable stars; Wesselink, from Adriaan J. Wesselink (1909-1995), Dutch/American astronomer, the originator of the method. → method.

Babinet compensator
  پاهنگنده‌ی ِ ببینه   
pâhangandeh-ye Babinet

Fr.: compensateur de Babinet   

A crystal device made of two → quartz  → prisms with equal acute angles assembled in a rhombus that is used in analyzing → polarized light. The wedge-shaped prisms are placed against each other and can be displaced along their plane of contact by a → micrometer. Thus they form a parallel plate of variable thickness allowing the optical retardation to be adjusted.

Jacques Babinet (1794-1872), French physicist; → compensator.

Babinet point
  نقطه‌ی ِ ببینه   
noqte-ye Babinet

Fr.: point de Babinet   

One of several points on the sky where the degree of → linear polarization is zero in skylight. See also → neutral point; → Arago point, → Brewster point.

Babinet compensator; → point.

Babinet's principle
  پروز ِ ببینه   
parvaz-e Babinet

Fr.: principe de Babinet   

The → diffraction pattern for an → aperture is the same as the diffraction pattern for its → complementary aperture.

Babinet compensator; → principle.

back
  پس، پشت   
pas (#), pošt (#)

Fr.: dos, arrière   

1) General: Related to or located at the back "the side or surface opposite the front or face."
2) The side of the → planispheric astrolabe opposite the hollow of the → mater, → tympanum, and → rete. At its center is hinged the → alidade, whose rim slides on a set of graduated circular scales engraved on the mater. The number of scales varies from one instrument to another. On this face the user can perform observations and read the data needed to set the front side of the instrument in the proper position (online museo galileo, VirtualMuseum).

Back, from M.E., from O.E. bæc; akin to O.H.G. bah "back."

Pas-, from pas "behind" (e.g.: pas-e pardé "behind the curtain"); Mid.Pers. pas "behind, before, after;" O.Pers. pasā "after;" Av. pasca "behind (of space); then, afterwards (of time);" cf. Skt. paścā "behind, after, later;" L. post "behind, in the rear; after, afterwards;" O.C.S. po "behind, after;" Lith. pas "at, by;" PIE *pos-, *posko-.
Pošt-, from pošt, variant of pas.

back-end
  پس-ته   
pas-tah

Fr.: back-end   

In a radiotelescope, the unit forming the end part of the reception chain. It generally consists of a spectrometer and performs frequency analysis of the signals. → front-end.

Back-end, from → back + end, from M.E., O.E. ende (cf. Du. einde, O.H.G. enti "top, forehead, end," Ger. ende, Goth. andeis "end"), originally "the opposite side," from PIE *antjo "end, boundary," from base *anta-/*anti- "opposite, in front of, before."

Pas-tah, from pas, → back, + tah "end," Mid.Pers. tah "bottom." The origin of this term is not clear. It may be related to Gk. tenagos "bottom, swamp," Latvian tigas<*tingas < *tenegos "depth," PIE *tenegos "water bottom."

background
  پس-زمینه، زمینه   
paszaminé, zaminé (#)

Fr.: fond   

General: That part of a view or scene that serves as a setting for the main objects, persons, etc.
Astro.: The part of an observed field which is not physically related to the objects of interest and lies behind them.

Background, from → back + ground, from M.E., from O.E. grund; akin to O.H.G. grunt "ground."

Paszaminé, from pas-, → back, + zaminé "ground," from zamin "ground," → earth.

foreground.

background noise
  نوفه‌ی ِ پس-زمینه، ~ زمینه   
nufe-ye paszaminé, ~ zaminé

Fr.: bruit du fond   

An unwanted signal in a system which is producing or recording a signal. For instance, a randomly fluctuating signal superimposed on the signal from a cosmic radio source.

background; → noise.

background radiation
  تابش ِ پس-زمینه، ~ زمینه   
tâbeš-e paszaminé, ~ zaminé

Fr.: rayonnement du fond   

The isotropic residual microwave radiation in space left from the primordial → Big Bang. Same as → cosmic microwave background (CMB) radiation.

background; → radiation.

backscatter
  ۱) پس-پراکندن ۲)، ۳) پس-پراکنش   
1) pas-parâkandan; 2), 3) pas-parâkaneš

Fr.: rétrodiffusion   

1) (v.tr.) To deflect photons or particles in a direction opposite to their initial path.
2) Same as → backscattering.
3) The radiation or particles so deflected.

From → back + → scattering.

<< < -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 > >>