Andromeda galaxy (M31, NGC 224)
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).
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.
An instrument for measuring and indicating the force or speed of the wind.
From Gk. anemos "wind" + → -meter.
Bâdsanj, from bâd "wind" + -sanj, → -meter.
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".
angle of deviation
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 of emergence
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 of incidence
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 of inclination
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.
angle of minimum deviation
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 of prism
Fr.: angle de prisme
→ prism angle.
angle of reflection
zâviye-ye bâztâb (#)
Fr.: angle de réflexion
The angle between the reflected ray and the normal to the reflecting surface.
angle of refraction
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.
Angstrom unit (Å)
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.
Having, forming, or consisting of an → angle or angles.
From L. angularis "having corners or angles," from angulus→ angle.
Zâviye-yi, adj. from zâviyé, → angle.
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.
tarâmun-e zâviye-yi, qotr-e ~
Fr.: diamètre angulaire
The apparent diameter of an object in angular measure.
angular diameter distance
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.
angular differential imaging (ADI)
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).
Fr.: dispersion angulaire
The rate of change of the angles of emergence θ of various wavelengths from a dispersing prism: dθ/dλ.
Fr.: distance angulaire