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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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autocorrelation function
  کریا‌ی ِ خودهم‌باز‌آنش   
karyâ-ye xod-hambâzâneš

Fr.: fonction d'autocorrélation   

A mathematical function that describes the correlation between two values of the same variable at different points in time.

autocorrelation; → function.

autocovariance function
  کریای ِ خود-هم‌ورتایی   
karyâ-ye xod-hamvartâyi

Fr.: fonction d'autocovariance   

The autocovariance function (ACF) is defined as the sequence of covariances of a stationary process.
A mathematical function that expresses the autocovariance of a series in terms of the interval of separation.

autocovariance; → function.

autonomous
  خوددات   
xoddât

Fr.: autonome   

1) Self-governing; independent; subject to its own laws only; having autonomy.
2) Pertaining to an autonomy, or a self-governing community.
3) Biology: Existing and functioning as an independent organism. Growing naturally or spontaneously, without cultivation (Dictionary.com).

Adjective from → autonomy.

autonomy
  خودداتی   
xoddâti

Fr.: autonomie   

1) Independence or freedom, as of the will or one's actions.
2) The condition of being autonomous; self-government or the right of self-government (Dictionary.com).

auto-; → -nomy.

average acceleration
  شتاب ِ میانگین   
šetâb-e miyângin

Fr.: accélération moyenne   

Of a body traveling from A to B, the change of → velocity divided by the time interval: ā = (v2 - v1) / (t2 - t1).

average; → acceleration.

averted vision
  نگاه ِ کژ   
negâh-e kaž (#)

Fr.: regard oblique   

The technique of looking slightly to the side of a faint object being studied while continuing to concentrate on the object. The technique helps bring out details which otherwise would be missed by looking directly at an object. The reason is that the portion of the eye's retina that best detects dim light (fovea) is located all around the edges rather than the center.

Averted p.p. from avert, from O.Fr. avertir, from L. avertere "to turn away," from → ab- "from, away" + vertere "to turn" (cognate with Pers. gardidan "to turn"); → vision.

Negâh, → vision; kaž "averted."

Avogadro constant
  پایای ِ آووگادرو   
pâyâ-ye Avogâdro (#)

Fr.: constante d'Avogadro   

The number of units in one → mole of any → substance (defined as its → molecular weight in grams), equal to 6.022 140 857 × 1023. The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance.

Named after Amedeo Avogadro (1776-1856), whose law allowed other physicists to calculate Avogadro's number; → number.

axial inclination
  درکیل ِ آسه   
darkil-e âsé

Fr.: inclinaison de l'axe   

The angle at which a planet's axis of rotation is tilted, with respect to that of the planet's orbit.

axial; → inclination.

axial precession
  پیشایان ِ آسه‌ای   
pišâyân-e âse-yi

Fr.: précession axiale   

1) A change in the orientation of the → rotation axis of a non-spherical, spinning body caused by → gravity. A rotating top will precess in a direction determined by the → torque exerted by its → weight. The precession → angular velocity is inversely proportional to the spin angular velocity, so that the precession is faster and more pronounced as the top slows down.
2) In particular, the gradual shift in the orientation of Earth's rotation axis which traces out a conical path once every ~ 26,000 years. The cause of the Earth's precession is the → equatorial bulge of the Earth, brought about by the → centrifugal force of the → rotation, which has changed the Earth from a perfect sphere to a slightly flattened one, thicker across the equator. The attraction of the Moon and Sun on the bulge is the reason which makes the Earth precess.

axial; → precession.

axiom of constraints
  بنداشت ِ پاوندها   
bondâšt-e pâvandhâ

Fr.: axiome des contraintes   

An axiom in → statics, stating that any → constrained body can be treated as a → free body detached from its → constraints, provided the latter are represented by their → reactions.

axiom; → constraint.

axion
  اکسیون   
aksion (#)

Fr.: axion   

A hypothetical weakly-interacting → boson of small mass required by models of → particle physics in order to solve the strong CP problem and explain a number of observed astrophysical/cosmological phenomena, including → dark matter, and the dimming of → type Ia → supernovae (→ accelerating Universe). Photons traveling in the → intergalactic medium would in part turn into axions in the presence of magnetic fields. The transformed photons are not detected on Earth and therefore supernovae would appear fainter even if the Universe is not accelerating.

Axion, first coined by Frank Wilczek (2004 Nobel Prize in Physics) apparently after a brand of washing detergent! The reason seems to be the idea that the particle will iron out a wrinkle in the → standard model of fundamental particles and forces while solving the problem of the Universe's → missing mass.

axis of rotation
  آسه‌ی ِ چرخش   
âse-ye carxeš

Fr.: axe de rotation   

Same as → rotation axis and → rotational axis.

axis; → rotation.

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.

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.

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.

balloon astronomy
  اخترشناسی با بالون، بالون-اخترشناسی   
axtaršenâsi bâ bâlon, bâlon-axtaršenâsi

Fr.: astronomie en ballon   

A branch of modern astronomy in which balloons are used to carry telescopes and instruments to high altitudes (up to 50 km) for observation.

Balloon, from Fr. ballon, from It. dialectal ballone, augmentative of balla, ball, from P.Gmc. *ball-, from PIE *bhel- "to blow, swell". → astronomy.

Axtaršenâsi, → astronomy; bâlon, from Fr. ballon.

balloon-borne telescope
  دوربین ِ بالون-برد، تلسکوپ ~   
durbin-e bâlon-bord, teleskop-e ~

Fr.: télescope porté par ballon   

A remotely guided or automatic telescope carried to high altitudes by a balloon.

balloon astronomy; borne "a past participle of bear," from O.E. beran "bear, bring, wear," from P.Gmc. *beranan (O.H.G. beran, Goth. bairan "to carry"), from PIE root *bher-; "to carry;" compare with Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother," Mod.Pers. bordan "to carry," Skt. bharati "he carries," Gk. pherein, L. fero "to carry." → telescope.

balloon astronomy. Bord in bâlon-bord "borne, carried," from Mod.Pers. bordan "to bear, carry," as explained above. Durbin, → telescope.

Balmer continuum
  پیوستار ِ بالمر   
peyvastâr-e Bâlmer

Fr.: continuum de Balmer   

A continuous range of wavelengths in the Balmer spectrum of hydrogen corresponding to transitions between the energy levels n = 2 and n = .

Balmer; → continuum.

Balmer discontinuity
  ناپیوستگی ِ بالمر   
nâpeyvastegi-ye Bâlmer

Fr.: discontinuité de Balmer   

An abrupt decrease in the intensity of the continuum at the limit of the → Balmer series of hydrogen (at about 3650 Å), caused by the energy absorbed when electrons originally in the second → energy level are ionized. Same as → Balmer jump.

Balmer; → discontinuity.

barrel distortion
  چولگی ِ چلیکی   
cowlegi-ye celiki (#)

Fr.: distortion en barillet   

A defect in an optical system in which magnification decreases with distance from the optical axis, whereby the image of a square appears barrel-shaped. Opposite of → pincushion distortion.

Barrel, M.E. barel, from O.Fr. baril; → distortion.

Cowlegi, → distortion; celiki, relating to celik "barrel".

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