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
Cherenkov radiation
  تابش ِ چرنکوف   
tâbeš-e Čerenkov (#)

rayonnement de Čerenkov   

Visible radiation emitted when → charged particles pass through a transparent medium faster than the speed of light in that medium.

Named after Pavel A. Čerenkov (1904-1990), Russian physicist, who discovered the phenomenon. He shared the Nobel prize 1958 in physics with Ilya Frank and Igor Tamm, who in 1937 gave the theoretical explanation for this radiation.

chi-square distribution
  واباژش ِ خی-دو   
vâbâžeš-e Xi-do

Fr.: loi du chi-deux   

A probability density function, denoted χ2, that gives the distribution of the sum of squares of k independent random variables, each being drawn from the normal distribution with zero mean and unit variance. The integer k is the number of degrees of freedom. The distribution has a positive skew; the skew is less with more degrees of freedom. As degrees of freedom increase, the chi-square distribution approaches a normal distribution. The most common application is chi-square tests for goodness of fit of an observed distribution to a theoretical one. If χ2 = 0 the agreement is perfect.

Chi Gk. letter of alphabet; → square; → distribution.

Vâbâžeš, → distribution; do, → two.

chromatic aberration
  بیراهش ِ رنگی   
birâheš-e rangi

Fr.: aberration chromatique   

A defect in a lens that causes it to concentrate the various colors in a beam of light at various point, thus producing color fringes.

chromatic; → aberration.

circular motion
  جنبش ِ دایره‌ای، ~ پرهونی   
jonbeš-e dâyere-yi, ~ parhuni

Fr.: mouvement circulaire   

Motion in which an object moves in a circle at a constant speed. The velocity, however, changes not because the magnitude of the velocity changes, but because its direction changes. The changing velocity creates an acceleration, called → centripetal acceleration. This acceleration results from the → centripetal force.

circular; → motion.

circular polarization
  قطبش ِ پرهونی، ~ دایره‌ای   
qotbeš-e parhuni, ~ dâyereyi (#)

Fr.: polarisation circulaire   

The → polarization of an → electromagnetic radiation in which the electric field vector describes a circle about the direction of propagation at any point in the path of the radiation. Circular polarization is a combination of two perpendicular → linearly polarized waves that are 90 degrees out of phase with each other. Circular polarization may be referred to as "right-hand" or "left-hand," depending on the rotation direction as viewed by the observer.

circular; → polarization.


Fr.: circulation   

The continuous movement of something from place to place or in an enclosed space. → meridional circulation.

M.E. circulacioun, from M.Fr. circulation or directly from L. circulationem, from circulare "to form a circle," from circulus "small ring," → circle.

Parhuneš, verbal noun from parhunidan, from parhun, → circle.


Fr.: circonspection   

Circumspect observation or action; caution; prudence.



Fr.: civilisation   

1) An advanced state of human society, in which a high level of culture, knowledge, production, and legal organization has been reached. The people or nations that have reached such a state.
2) The act or process of civilizing or being civilized.

verbal noun of → civilize.

Clapeyron equation
  هموگش ِ کلاپرون   
hamugeš-e Clapeyron

Fr.: équation de Clapeyron   

An equation that relates the temperature and pressure dependence of phases in equilibrium with the heat interaction and volume change associated with a phase change: dP/dT = L/T ΔV, where dP/dT is the slope of the coexistence curve, L is the → latent heat, T is the temperature, and ΔV is the volume change of the phase transition.

Named after Émile Clapeyron (1799-1864), a French engineer and physicist, one of the founders of → thermodynamics; → equation.

  آرونش، رونه‌کرد   
âruneš, runekard

Fr.: clarification   

The action of making a statement or situation less confused and more comprehensible.

Verbal noun of → clarify.

  رده بندی   
radebandi (#)

Fr.: classification   

The systematic grouping of astronomical objects into categories on the basis of physical, morphological, or evolutionary characteristics.

Classification, from O.Fr., from classifier, from → class + -fier, from L. -ficare, root of facere "to make, do;" PIE base *dhe- "to put, to do" (cf. Skt. dadhati "puts, places;" Av. dadaiti "he puts," O.Pers. ada "he made," Gk. tithenai "to put, set, place."

Radebandi, from radé, → class, + bandi, verbal noun of bastan "to bind, shut; to get, acquire, incur," from Mid.Pers. bastan/vastan "to bind, shut;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie;" cf. Skt. bandh- "to bind, tie, fasten;" Ger. binden, E. bind, → band; PIE base *bhendh- "to bind."

Clausius equation
  هموگش ِ کلاؤزیوس   
hamugeš-e Clausius

Fr.: équation de Clausius   

A first-order improvement on the → ideal gas law that corrects for the finite volume of molecules.

After Rudolf Clausius (1822-1888), a German physicist and mathematician, → equation.

Clausius-Clapeyron equation
  هموگش ِ کلاؤزیوس-کلاپرون   
hamugeš-e Clausius-Clapeyron

Fr.: équation de Clausius-Clapeyron   

An approximation of the → Clapeyron equation for liquid-vapor equilibrium that incorporates the → ideal gas law and states that the logarithm of vapor pressure is inversely proportional to temperature.

Clausius equation; → Clapeyron equation.

cloud fragmentation
  لتپارش ِ ابر   
latpâreš-e abr

Fr.: fragmentation de nuage   

Process by which a → collapsing → giant molecular cloud breaks into dense → clumps, eventually bringing about → pre-stellar cores.

cloud; → fragmentation.

cluster formation efficiency (CFE)
  کارایی ِ دیسش ِ خوشه   
kârâyiè-ye diseš-e xuše

Fr.: efficacité de formation d'amas   

The fraction of → star formation which happens in → bound clusters. It is defined as the ratio between the → cluster formation rate and → star formation rate (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

cluster; → formation; → efficiency.

cluster formation rate (CFR)
  نرخ ِ دیسش ِ خوشه   
nerx-e diseš-e xuše

Fr.: taux de formation d'amas   

A parameter used in star formation models representing the ratio of the total mass in → star clusters to the corresponding age range (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

cluster; → formation; → rate.

cluster mass function (CMF)
  کریای ِ جرم ِ خوشه   
karyâ-ye jerm-e xušé

Fr.: fonction de masse d'amas   

An empirical power-law relation representing the number of clusters as a function of their mass. It is defined as: N(M)dM ∝ MdM, where the exponent α has an estimated value of about 2 and dM is the mass interval. It is believed that this is a universal law applying to a variety of objects including globular clusters, massive young clusters, and H II regions.

cluster; → mass; → function.

CO formation
  دیسش ِ CO   
diseš-e CO

Fr.: formation de CO   

The chemical reaction that gives rise to → carbon monoxide in the → interstellar medium. According to models, several processes may lead to CO formation. For example, HCO+ + e → CO + H. The molecule HCO+ is itself produced through several paths, for example: H3+ + C → CH2+ + H, CH2+ + H2 → CH3+ + H, CH3+ + O → HCO+ + H. Alternatively: C+ + H2O → HCO+ + H. Another possibility: C+ + OH → CO+ + H, CO+ + H2→ HCO+ + H.

carbon monoxide; → formation.

co-formation theory
  نگره‌ی ِ هم-دیسش   
negare-ye ham-diseš

Fr.: théorie de co-formation   

A theory according to which the Earth and Moon formed from the → protoplanetary disk at the same time. See also → giant impact hypothesis, → capture theory, → fission theory.

co-; → formation; → theory.

co-orbital motion
  جنبش ِ هم‌مداری   
jonbeš-e ham-madâri

Fr.: mouvement co-orbital   

The motion of two or more bodies around the Sun on different orbits when it takes them the same amount of time to complete one revolution. There are three possible types of co-orbital motions of a small body associated with a planet: → tadpole orbits, → horseshoe orbits, and → quasi-satellite orbits.

co-orbital; → motion.

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