An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 696
effective temperature
  دمای ِ ا ُسکرمند   
damâ-ye oskarmand

Fr.: température effective   

A measure of the surface temperature of a star derived from the total emitted energy, assuming that the star is a → blackbody emitter (→ Stefan-Boltzmann law, → Planck's radiation law). See also → brightness temperature; → color temperature.

effective; → temperature.


Fr.: effectivité   

The degree to which goals are achieved and the extent to which posed problems are solved. Compare → efficiency.

effective; → -ness.


Fr.: efficacité   

Power or capacity to produce a desired effect; → effectiveness.

From L. efficacia "efficacy, efficiency," from efficax "powerful, effectual, efficient," from stem of efficere "accomplish," → effect.

Oskarmandi, → effectiveness.

kârâyi (#)

Fr.: efficacité   

1) The state or quality of being efficient; competence. Compare → effectiveness.
Of a machine, engine, or device, the ratio of the physical quantity which may be stored, transferred, or transformed to the total input quantity.

L efficientia, from efficient-, → effect, + -ia "-y," an E. suffix of adjectives.

Kârâyi, from kârâ "efficient," from kâr, → work + â present stem of âmadan "to come," from Av. ay- "to go, to come," aēiti "goes," O.Pers. aitiy "goes," Skt. e- "to come near," eti "arrival," Gk. eimi "I go," L. eo "I go," Tokharian AB i-; PIE *ei- "to go, to walk."


Fr.: efflux   

Outward flow of a → liquid. Something that → flows out.

L. effluxus, p.p. of effluere "to flow out," from → ex- "out" + fluere "to flow," → flux.

Zošâr, from zo- "out of, from," → ex-, + šâr, → flux.

  تخم، خاگ   
toxm, xâg

Fr.: œuf   

1) An oval or round object laid by a female bird, reptile, fish, or invertebrate, usually containing a developing embryo. The eggs of birds are enclosed in a chalky shell, while those of reptiles are in a leathery membrane.
2) Biology: The female reproductive cell in animals and plants; an ovum (

M.E., from Old Norse egg, cognate with O.Saxon, M.Du., Du., O.H.G., Ger. Ei, probably from PIE *owyo-/*oyyo- "egg;" source of Pers. xâg, as below.

Toxm, → seed.
Xâg "egg," Lori, Laki , Pash. "egg," Ossetic ajk "egg," Bojnurdi hek "egg," Khotanese āhaa- "egg;" variant xâyé "egg; testicle;" Mid.Pers. xâyak "egg;" Av. aēm/aiam "egg;" cf. Gk. oion, L. ovum; Goth. ada; O.E. æg; Ger. Ei; PIE *owyo-/*oyyo- "egg."


Fr.: émersion   

The reappearance of a celestial body after an eclipse, an occultation, or a transit; same as emersion. → ingress.

From L. egressus, from egredi "to go out," from → ex- "out" + -gredi, comb. form of gradi "to walk, go, step;" from PIE *ghredh- (cf. Lith. gridiju "to go, wander," O.C.S. gredo "to come").

Osgâm "going out," from os- "out," → ex-, + gâm "step, pace," Mid.Pers. gâm, O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes," Mod.Pers. âmadan "to come," Skt. gamati "goes," Gk. bainein "to go, walk, step," L. venire "to come," Tocharian A käm- "to come," O.H.G. queman "to come," E. come; PIE root *gwem- "to go, come."

EHB star
  ستاره‌ی ِ EHB   
setâre-ye EHB

Fr.: étoile EBH   

Same as → extreme horizontal branch star.

extreme horizontal branch star.


Fr.: fonction propre   

1) Math.: An → eigenvector for a linear → operator on a → vector space whose vectors are → functions. Also known as proper function.
2) Quantum mechanics: A → wave function corresponding to an → eigenvalue. Eigenfunctions represent the stationary → quantum states of a system.

From Ger. Eigenfunktion, from eigen- "characteristic, particular, own" (from P.Gmc. *aigana- "possessed, owned," Du. eigen, O.E. agen "one's own") + → function.

Viž-karyâ, from viž, contraction of vižé "particular, charcteristic" + karyâ, → function. Vižé, from Mid.Pers. apēcak "pure, sacred," from *apa-vēcak "set apart," from prefix apa- + vēcak, from vēxtan (Mod.Pers. bixtan) "to detach, separate, sift, remove," Av. vaēk- "to select, sort out, sift," pr. vaēca-, Skt. vic-, vinakti "to sift, winnow, separate; to inquire."

  ویژ حالت   

Fr.: état propre   

Quantum mechanics: A dynamical state whose state vector (or wave function) is an → eigenvector of an → operator corresponding to a specified physical quantity.

eigenfunction; → state.

  ویژ ارزه   

Fr.: valeur propre   

1) Math.: The one of the → scalars λ such that T(v) = λv, where T is a linear → operator on a → vector space, and v is an → eigenvector.
2) Quantum mechanics: The specified values of → quantized energy for which the → Schrodinger equation is soluble, subject to the appropriate → boundary conditions.

eigenfunction; → value.


Fr.: vecteur propre   

Math.: A nonzero vector v whose direction is not changed by a given linear transformation T; that is, T(v) = λ v for some scalar λ.

eigenfunction; → vector.

hašt (#)

Fr.: huit   

A → cardinal number between → seven and → nine.

M.E. eighte, from O.E. eahta, æhta, related to O.Norse atta, Swed. åtta, Du. acht, O.H.G. Ahto, Ger. acht; Pars. hašt, as below, from PIE *okto(u) "eight."

Hašt, from Mid.Pers. hašt; Av. ašta; cognate with Skt. asta; Gk. okto; L. octo (from which It. otto, Sp. ocho, Fr. huit).

einstein (#)

Fr.: einstein   

A unit of radiation energy sometimes used in the investigation of photochemical processes. The unit is defined as NA, where NA is → Avogadro's number and is the energy of a → quantum of the radiation. One einstein (or Einstein unit) is the energy per → mole of photons carried by a beam of monochromatic light.

Named for Albert Einstein (1879-1955).

Einstein coefficient
  همگر ِ اینشتین   
hamgar-e Einstein

Fr.: coefficient d'Einstein   

A measure of the probability that a particular atomic transition leading to the formation of an atomic spectral line occurs. The coefficient of spontaneous emission is denoted by Aij, and the coefficient of stimulated emission by Bij, i representing the lower level and j is the upper level.

Named after Albert Einstein (1879-1955) who introduced the coefficients in 1916; → coefficient.

Einstein cross
  چلیپای ِ اینشتین   
calipâ-ye Einstein

Fr.: croix d'Einstein   

An image of a distant quasar (redshift 1.7) formed by a foreground spiral galaxy (redshift 0.039) through gravitational lensing. The image of the quasar is split into four point sources forming a cross at the center of the galaxy.

Einstein; → cross.

Einstein equivalence principle
  پروز ِ هموگ-ارزی ِ اینشتین   
parvaz-e hamug-arzi-ye Einstein

Fr.: principe d'équivalence d'Einstein   

The → equivalence principle as stated by Einstein, on which is based the theory of → general relativity. It comprises the three following items:
1) The → weak equivalence principle is valid.
2) The outcome of any local non-gravitational experiment is independent of the velocity of the freely-falling → reference frame in which it is performed. Also known as → local Lorentz invariance.
3) The outcome of any local non-gravitational experiment is independent of where and when in the Universe it is performed. Also called → local position invariance.

Einstein; → equivalence; → principle.

Einstein model
  مدل ِ اینشتین   
model-e Einstein

Fr.: modèle d'Einstein   

A model for the → specific heat of solids in which the specific heat is due to the vibrations of the atoms of the solids. The vibration energy is → quantized and the atoms have a single frequency, ν. Put forward in 1907 by Einstein, this model was the first application of → quantum theory to the solid state physics. The expression for the specific heat is given by: CV = 3Rx2ex/(ex -1)2, where R is the → gas constant, x = TE/T, TE = hν/k, h is → Planck's constant, and k is → Boltzmann's constant. TE is called the → Einstein temperature. This model could explain the temperature behavior of specific heat but not very satisfactorily at low temperatures. It has therefore been superseded by the → Debye model. See also → Dulong-Petit law.

Albert Einstein in 1907; → model.

Einstein notation
  نمادگان ِ اینشتین   
namâdgân-e Einstein

Fr.: convention Einstein   

A notation convention in → tensor analysis whereby whenever there is an expression with a repeated → index, the summation is done over that index from 1 to 3 (or from 1 to n, where n is the space dimension). For example, the dot product of vectors a and b is usually written as: a.b = Σ (i = 1 to 3) In the Einstein notation this is simply written as a.b = This notation makes operations much easier. Same as Einstein summation convention.

Einstein; → notation.

Einstein radius
  شعاع ِ اینشتین   
šo'â'-e Einstein

Fr.: rayon d'Einstein   

In gravitational lens phenomenon, the critical distance from the → lensing object for which the light ray from the source is deflected to the observer, provided that the source, the lens, and the observer are exactly aligned. Consider a massive object (the lens) situated exactly on the line of sight from Earth to a background source. The light rays from the source passing the lens at different distances are bent toward the lens. Since the bending angle for a light ray increases with decreasing distance from the lens, there is a critical distance such that the ray will be deflected just enough to hit the Earth. This distance is called the Einstein radius. By rotational symmetry about the Earth-source axis, an observer on Earth with perfect resolution would see the source lensed into an annulus, called Einstein ring, centered on its position. The size of an Einstein ring is given by the Einstein radius: θE = (4GM/c2)0.5 (dLS/(dL.dS)0.5, where G is the → gravitational constant, M is the mass of the lens, c is the → speed of light, dL is the angular diameter distance to the lens, dS is the angular diameter distance to the source, and dLS is the angular diameter distance between the lens and the source. The equation can be simplified to: θE = (0''.9) (M/1011Msun)0.5 (D/Gpc)-0.5. Hence, for a dense cluster with mass M ~ 10 × 1015 Msun at a distance of 1 Gigaparsec (1 Gpc) this radius is about 100 arcsec. For a gravitational → microlensing event (with masses of order 1 Msun) at galactic distances (say D ~ 3 kpc), the typical Einstein radius would be of order milli-arcseconds.

Einstein; → radius.

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