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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 929
Andromeda
  آندرومدا، زن ِ به زنجیر بسته   
Ândromedâ, Zan-e bé Zanjir Basté (#)

Fr.: Andromède   

A northern constellation between → Perseus and → Pegasus located at approximately R.A. 1h, Dec. +40 deg. Abbreviation And, Genitive form Andromedae.

In Gk. mythology, Andromeda was the princess of Ethiopia, daughter of → Cepheus and → Cassiopeia. The queen Cassiopeia angered Poseidon by saying that Andromeda (or possibly Cassiopeia herself) was more beautiful than the Nereids. Poseidon sent a sea monster to prey upon the country; he could be appeased only by the sacrifice of the king's daughter. Andromeda in sacrifice was chained to a rock by the sea; but she was rescued by → Perseus, who killed the monster and later married her. Cassiopeia, Cepheus, and Andromeda were all set among the stars as constellations.

Zan-e bé Zanjir Basté "the chained woman," coined by the 11th century astronomer Biruni, from Ar. Emra'at al-mosalsalah "the chained woman," from the Gk. mythology.

Andromeda galaxy (M31, NGC 224)
  کهکشان ِ آندرومدا، ~ زن ِ به زنجیر بسته   
kahkašân-e Ândromedâ (#), ~ Zan-e bé Zanjir Basté (#)

Fr.: galaxie d'Andromède   

The nearest → spiral galaxy to our own and a major member of the → Local Group. It lies in the constellation → Andromeda and is the most remote object normally visible to the naked eye. The earliest known reference to this galaxy is by the Iranian astronomer Sufi who called it "the little cloud" in his Book of Fixed Stars (A.D. 964).

Andromeda; → galaxy.

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.

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