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
Andromedids
  آندرومداییان   
Ândromedâiyân

Fr.: Andromédides   

A meteor shower which appears about 25 November with its → radiant located in the constellation → Andromeda. The Andromedids are the debris of → Biela's comet. The short-period comet, discovered in 1826, split into two parts in the middle of the 19th century and later vanished. Hence their alternative name Bielids.

Andromedids, from Andromeda constellation + → -ids suffix denoting "descendant of, belonging to the family of."

Ândromedâiyân, from Ândromedâ + -iyân, → -ids.

anemometer
  بادسنج   
bâdsanj (#)

Fr.: anémomètre   

An instrument for measuring and indicating the force or speed of the wind.

From Gk. anemos "wind" + → -meter.

Bâdsanj, from bâd "wind" + -sanj, → -meter.

angle
  زاویه، گوشه، کنج   
zâviyé, gušé, konj

Fr.: angle   

The figure formed by two lines extending from a common point; the figure formed by two intersecting planes (dihedral angle).

L. angulum (nominative angulus) "corner," a dim. form from PIE *ang-/*ank- "to bend;" cf. Skt. ankah "hook, bent," Gk. angkon "elbow," angkura "anchor," Lith. anka "loop," O.E. ancleo "ankle," O.H.G. ango "hook," Av. ank- "curved, crooked," Av. angušta- "toe," Mod.Pers. angošt, angol, angul "finger".

Zâviyé from Ar. zâwiyat "corner, angle".
Gušé "corner, angle," Mid.Pers. gošak "corner."
Konj, "angle, corner," → diagonal.

angle of deviation
  زاویه‌ی ِ کژرفت   
zâviye-ye kažraft

Fr.: angle de déviation   

The angle between the → incident ray of light entering an → optical system (such as a prism) and the → refracted ray that emerges from the system. Because of the different indices of refraction for the different wavelengths of visible light, the angle of deviation varies with wavelength.

angle; → deviation.

angle of emergence
  زاویه‌ی ِ زمرچش   
zâviye-ye zomarceš

Fr.: angle d'émergence   

The angle of the light coming out of a medium. For a medium with parallel sides (such as a glass slab) it is equal to the angle of incidence.

angle; → emergence.

angle of incidence
  زاویه‌ی ِ فتاد   
zâviye-ye fotâd

Fr.: angle d'incidence   

The angle formed between a ray of light striking a surface and the normal to that surface at the point of incidence. Also called → incidence angle.

angle; → incidence.

angle of inclination
  زاویه‌ی ِ درکیل   
zâviye-ye darkil

Fr.: angle d'inclinaison   

1) General: The angle between one plane and another, or the angle formed by a reference axis and a given line.
2) Binary systems: The angle between the plane of the orbit and the → plane of the sky.
3) Rotating stars: The angle between the → equatorial plane and the → plane of the sky.

angle; → inclination.

angle of minimum deviation
  زاویه‌ی ِ کژرفت ِ کمینه   
zâviye-ye kažraft kaminé

Fr.: angle de déviation minimale   

The angle between the light entering and exiting the prism when the light passing through the prism is parallel to the prism's base. Angle of minimum deviation (D) is used to measure the → index of refraction (n) of the prism glass, because: n = sin [(A + D)/2]/sin (A/2), where A is the → prism angle.

angle; → minimum; → deviation.

angle of prism
  زاویه‌ی ِ منشور   
zâviye-ye manšur

Fr.: angle de prisme   

prism angle.

angle; → prism.

angle of reflection
  زاویه‌ی ِ بازتاب   
zâviye-ye bâztâb (#)

Fr.: angle de réflexion   

The angle between the reflected ray and the normal to the reflecting surface.

angle; → reflection.

angle of refraction
  زاویه‌ی ِ شکست   
zâviye-yé šekast (#)

Fr.: angle de réfraction   

The angle between the direction in which a ray is refracted and the normal to the refracting surface.

angle; → refraction.

Angstrom unit (Å)
  یکا‌ی ِ آنگستروم   
yekâ-ye Ângštrom

Fr.: unité d'Ångström   

Unit of length used to describe wavelengths and interatomic distances. 1 Å = 10-10 m.

Named after Anders Jonas Ångström, Swedish physicist and astronomer who founded the science of spectroscopy and discovered by studying the solar spectrum that there is hydrogen in the Sun's atmosphere; → unit.

angular
  زاویه‌ای   
zâviye-yi (#)

Fr.: angulaire   

Having, forming, or consisting of an → angle or angles.

From L. angularis "having corners or angles," from angulusangle.

Zâviye-yi, adj. from zâviyé, → angle.

angular acceleration
  شتاب ِ زاویه‌ای   
šetâb-e zâviye-yi

Fr.: accélération angulaire   

The rate of change of → angular velocity. It is equal to the → first derivative of the → angular velocity: α = dω/dt =d2θ/dt2 = at/r, where θ is the angle rotated, at is the linear tangential acceleration, and r is the radius of circular path.

angular; → acceleration.

angular diameter
  ترامون ِ زاویه‌ای، قطر ِ ~   
tarâmun-e zâviye-yi, qotr-e ~

Fr.: diamètre angulaire   

The apparent diameter of an object in angular measure.

angular; → diameter.

angular diameter distance
  اپست ِ زاویه‌ای   
apest-e zâviye-yi

Fr.: distance angulaire   

1) The ratio of an object's → linear size (l) to its → angular size (δθ, in → radians), that is DA = l/δθ. It is used to convert observed angular separations into proper separations at the source.

2) In cosmology, a distance defined as the ratio of an object's physical transverse size (l) to its angular size (δθ). It is used to convert angular separations in telescope images into proper separations at the source. The angular diameter distance is defined by: DA = l / δθ. Consider a light source of size l at r = r1 and t = t1 subtending an angle δθ at the origin (r = 0, t = t0). The proper distance between the two ends of the object is related to δθ by: δθ = l / [a(t1). r1], where a(t1) is the → scale factor at the present epoch. Therefore, DA = r1 / (1 + z). The angular diameter distance has the particularity that it does not increase infinitely with z→ ∞. It gets its maximum value at a → redshift of ~ 1 and then decreases for higher z. Therefore, more distant objects appear larger in angular size. This is explained by considering the size of the Universe when the light of the object was emitted. At that time the Universe was smaller and therefore the object occupied a larger fraction of the size of the Universe. In other words, objects appear larger because the entire Universe acts as a → gravitational lense.

angular; → diameter; → distance.

angular differential imaging (ADI)
  تصویرگری ِ دگرسانه‌ای ِ زاویه‌ای   
tasvigari-ye degarsâne-yi-ye zâviye-yi

Fr.: imagerie différentielle angulaire   

A high-contrast imaging technique that reduces minute temporal and spatial → seeing fluctuations and facilitates the detection of faint point sources, in close separation from their stars. It consists of the acquisition of a sequence of images with an → altazimuth mounting telescope while the instrument field derotator is switched off. This keeps the instrument and telescope optics aligned and allows the field of view to rotate with respect to the instrument. For each image, a reference → point spread function (PSF) is constructed from other appropriately selected images of the same sequence and subtracted to remove quasistatic PSF structure (Marois et al. 2006, ApJ 641, 556).

angular; → differential; → imaging.

angular dispersion
  پاشش ِ زاویه‌ای   
pâšeš-e zâvie-yi

Fr.: dispersion angulaire   

The rate of change of the angles of emergence θ of various wavelengths from a dispersing prism: dθ/dλ.

angular; → dispersion.

angular distance
  اپست ِ زاویه‌ای   
apest-e zâviye-yi

Fr.: distance angulaire   

Between two points A and B, the angle → subtended by lines drawn from an observing point O to A and B. Same as → angular separation.

angular; → distance.

angular frequency
  بسامد ِ زاویه‌ای   
basâmad-e zaviye-yi (#)

Fr.: fréquence angulaire   

The number of complete rotations per unit time, expressed in radian per second: ω = 2πν, where ν is the frequency (cycles per second).

angular; → frequency.

<< < -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 > >>