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
cross dispersion
  پاشش چلیپایی، ~ خاجی   
pâšeš-e calipâyi, ~ xâji

Fr.: dispersion croisée   

Dispersion of a light beam by using two dispersing elements (grating, grism), one for separating spectral orders, the other for resolving spectral features within an order.

cross; → dispersion.

cross identification
  ایدانش ِ چلیپایی   
idâneš-e calipâyi

Fr.: identification croisée   

The identification of an object in a data base or catalog and matching it with the same object identified in another catalog.

cross; → identification.

cross section

Fr.: 1) section plane; 2) section efficace   

1) Math: The intersection of a plane with a geometric figure, usually at right angles to an axis of symmetry.
2) Physics: A quantity that expresses the effective area that a given particle presents as a target to another incident particle, giving a measure of the probability that the incident particle will induce a particular atomic or nuclear reaction. Also called collision cross section. The cross section has the dimensions of a surface. In nuclear and particle physics, the commonly used units for the cross section are the barn and cm2.

In classical mechanics, the cross section for the collision of a point particle with a hard sphere is just be the surface of a section through the middle of the sphere. This explains the name "cross section." → cross; → section.


Fr.: cristallisation   

A process by which a homogeneous solution becomes crystal.

Noun from crystallize, → crystal.

Noun from bolur, from verb boluridan "to crystallize" + verbal noun suffix -eš.

cubic equation
  هموگش ِ کابی   
hamugeš-e kâbi

Fr.: équation cubique   

An equation containing unknowns of the third power; the general form: ax3 + bx2 + cx + d = 0.

Cubic, of or pertaining to → cube; → equation.

cubic function
  کریای ِ کابی   
karyâ-ye kâbi

Fr.: fonction cubique   

A function defined by a → polynomial of → degree three. Its generalized form is: f(x) = ax3 + bx2 + cx + d, where a, b, c and d are constants, and a≠ 0.

cubic; → function.


Fr.: culmination   

The act of culminating or the instant at which a celestial object reaches its highest altitude above the horizon by crossing the observer's meridian. → upper culmination; → lower culmination.

Verbal noun of → culminate.

Bâlest, from Mid.Pers. bâlist "culmination point of a star; highest, summit," from bâlây "high" + -ist superlative suffix, Av. barəzišta- "highest," from barəz- "high, mount" (Skt. bhrant- "high," O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress," Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- "high") + -išta- superlative suffix (Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost).

cumulative distribution function
  کریای ِ واباژش ِ کومشی   
karyâ-ye vâbâžeš-e kumeši

Fr.: fonction de distribution cumulée   

A function that gives the probability that a → random variable X is less than or equal to x, at each possible outcome: F(x) = P(X ≤ x), for -∞ < x < ∞. Same as → distribution function.

cumulative; → distribution; → function.

Cygnus OB association
  آهزش ِ OB ماکیان   
âhazeš-e OB Mâkiyân

Fr.: association OB Cygne   

One of nine → OB associations located in the Cygnus → constellation. The central association, → Cygnus OB2, is the most famous and the youngest of the Cygnus region. (L. Mahy et al. 2013, astro-ph/1301.0500 and references therein).

Cygnus; → OB star; → association.

D-type ionization front
  پیشان ِ یونش ِ گونه‌ی ِ D   
pišân-e yoneš-e gune-ye D

Fr.: front d'ionisation de type D   

An → ionization front of → H II regions whose expansion speed is comparable to the → sound speed in the gas (~ 10 km/sec for hydrogen at 104 K). A D-type ionization front results from → R-type ionization front when its propagation speed decreases as the volume of gas ahead of the ionization front grows. If front velocity is equal to a lower limit (C12 / 2C2, where C1 and C2 are the sound speed ahead and behind the front respectively), the front is called D critical.

D referring to a dense gas; → type; → ionization; → front.

dark adaptation
  نیاوش به تاریکی   
niyâveš bé târiki

Fr.: adaptation à l'obscurité   

The automatic adjustment of the iris and retina of the eye to allow maximum vision in the dark, following exposure of the eye to a relatively brighter illumination.

dark; → adaptation.

dark matter annihilation
  نابودی ِ ماده‌ی ِ تاریک   
nâbudi-ye mâde-ye târik

Fr.: annihilation de la matière noire   

A hypothetical process whereby hypothetical → non-baryonic dark matter particles undergo → annihilation interactions with themselves. The process results in observable by-products such as high-energy photons, neutrinos, and other detectable particles. See also → dark matter decay.

dark; → matter; → annihilation.

data acquisition
  الفنجش ِ داده‌ها   
alfanješ-e dâdehâ

Fr.: acquisition de données   

The process of controlling telescope operations during observation and obtaining data.

data; acquisition, from L. acquisitionem, from acquirere "get in addition," from → ad- "extra" + quærere "to search for, obtain."

Alfanješ, verbal noun of alfanjidan (variant alfaqdan) "to acquire, get," Bactrian αλφανζ "to acquire," Sogdian δβ'yz "to acquire, gain, get" (Cheung 2007); → data.

data reduction
  بازهازش ِ داده‌ها   
bâzhâzeš-e dâdehâ

Fr.: réduction de données   

The process of converting crude observational data into usable information for scientific interpretation, by correcting, rearranging, ordering, and simplifying.

data; → reduction.

de Broglie equation
  هموگش ِ دوبروی   
hamugeš-e de Broglie

Fr.: équation de de Broglie   

According to the → de Broglie hypothesis, which has been verified by experiments, every → particle of matter, whatever its nature, has a characteristic → wavelength associated with its wavelike quantum aspect. The de Broglie equation gives the equivalent wavelength of a moving particle: λ = h/mv, where h is → Planck's constant, m the mass of the particle, and v its velocity.
See also: → de Broglie wavelength, → Davisson-Germer experiment.

Named after Louis Victor de Broglie (1892-1987), French physicist, creator of a new field in physics, wave mechanics, who won the Nobel prize in physics in 1929. → equation

  فرو انگیزش   

Fr.: désexcitation   

Transition from an excited energy state to a lower energy level, as in spectral line formation or particle emission from an atomic nucleus.

From → de- + → excitation.


Fr.: déprojection   

A method for estimating the real orientation of a field and/or related velocities/separations from two-dimensional images.

de-; → projection.

vâšetâb (#)

Fr.: décéleration   

The act or process of moving, or of causing to move, with decreasing speed. Sometimes called negative acceleration.

Verbal noun of decelerate.

deceleration parameter
  پارامون ِ واشتاب   
pârâmun-e vâšetâb

Fr.: paramètre de décéleration   

A parameter designating the rate at which the expansion of the Universe would slow down owing to the braking gravitational effect of the matter content of the Universe. It is expressed by: q(t) = -R(t)R ..(t)/R .2(t), where R(t) represents the size of the Universe at time t. See also → expansion parameter; compare with → acceleration parameter.

deceleration; → parameter.

decimal fraction
  برخه‌ی ِ دهدهی   
barxe-ye dahdahi

Fr.: fraction décimale   

A fraction expressed by using → decimal representation, as opposed to a vulgar fraction. For example, 2/5 is a vulgar fraction; 0.40 is a decimal fraction.

decimal; → fraction.

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