An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1965 Search : ion
ambipolar diffusion
  پخش ِ اوبا قطبی   
paxš-e ubâqotbi

Fr.: diffusion ambipolaire   

A physical process which allows a → molecular cloud to decouple from → interstellar magnetic field in order to undergo → gravitational collapse. A cloud of pure molecular gas would form stars very fast through collapse since neutral matter does not respond to the magnetic field. However, the magnetic field holds up a collapse because the ions present in the cloud collide with the neutrals and tie them to the field. The collapse can then only proceed if the magnetic field can be separated from the gas. In denser molecular cores the ionization degree decreases substantially and therefore neutrals and ions decouple.

ambipolar; → diffusion.

  دامنه‌دهی، دامنه‌گیری   
dâmane-dehi, dâmane-giri (#)

Fr.: amplification   

1) General: The act or result of amplifying, enlarging, or extending.
2) Physics: The process of increasing the magnitude of a variable quantity, especially the magnitude of voltage, power, or current, without altering any other quantity.

Verbal noun of → amplify.

amplification factor
  کروند ِ دامنه‌دهی   
karvand-e dâmane-dahi

Fr.: facteur d'amplification   

1) Electronics: The extent to which an → analogue → amplifier boosts the strength of a → signal. Also called → gain.
2) In → gravitational lensing, the ratio of the lensed brightness to unlensed brightness. This factor depends on the mass of the → lensing object and the closeness of the alignment between observer, lens, and source (→ impact parameter).

amplification; → factor.

analytic function
  کریای ِ آنالسی   
karyâ-ye ânâlasi

Fr.: fonction analytique   

A function which can be represented by a convergent → power series.

analytic; → function.

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 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 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.

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 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 resolution
  واگشود ِ زاویه‌ای   
vâgošud-e zâviye-yi

Fr.: résolution angulaire   

Of a telescope, the smallest angle betwwen two → point sources that produces distinct images. It depends on both the wavelength at which observations are made and on the diameter of the telescope. Same as → spatial resolution.

angular; → resolution.

angular separation
  جدایی ِ زاویه‌ای   
jodâyiye zâviye-yi

Fr.: séparation angulaire   

Same as → angular distance.

angular; → separation.


Fr.: animation   

1) An act or instance of animating or enlivening; the state or condition of being animated.
2) The technique of imaging successive drawings or positions of cartoons to create an illusion of movement when the film is shown as a sequence.

animate; → -tion.

ânion (#)

Fr.: anion   

A → negatively charged → ion or → radical. Anions in a liquid subjected to electric potential are attracted toward the → anode. See also → cation.

From Gk. anienai "to go up," from an-, from → ana- "up," + -i-, from ire, eo "to go, walk," cf. Pers. ây-, → assembly, + -on, as in → ion.

nâbudi (#)

Fr.: annihilation   

The process in which the entire → mass of → two colliding → particles, one of → matter and one of → antimatter, is → converted into → radiant energy in the form of → gamma rays. See also → annihilation operator.

L. annihilatus, p.p. of annihilare "to reduce to nothing," from ad- "to" + nihil "nothing," from ne- "not" + hilum "small thing, trifle"

Nâbudi, from nâ- "not" + bud "to be, exist," from budan "to be, exist" + -i noun forming suffix.

annihilation operator
  آپارگر ِ نابودی   
âpârgar-e nâbudi

Fr.: opérateur d'annihilation   

In → quantum field theory, the operator that lowers → eigenstates one → energy level, contrarily to the → creation operator.

annihilation; → operator.

annual aberration
  بیراهش ِ سالانه   
birâheš-e sâlâné

Fr.: aberration annuelle   

The apparent, small displacement in position of a star during the year due to the → aberration of starlight. It depends on the → celestial latitude, and its maximum value is about 20''.50. See also → constant of aberration; → aberration orbit.

annual; → aberration.

annual apparent motion
  جنبش ِ سالانه‌ی ِ پدیدار   
jonbeš-e sâlâne-ye padidâr

Fr.: mouvement annuel apparent   

annual motion.

annual; → apparent; → motion.

annual equation
  هموگش ِ سالانه   
hamugeš-e sâlâné

Fr.: équation annuelle   

An irregularity in the Moon's orbit, which can amount to 11 degrees in a period of one year. It results from the Sun's disturbing effect on the motion of the Moon due to varying distance between them.

annual; → equation.

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