An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 435 Search : ad
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.

Chladni pattern
  الگوی ِ کلادنی   
olgu-ye Chladni

Fr.: figure de Chladni   

A pattern formed by fine powder or salt placed on a vibrating surface. The figures display the positions of → nodes and → antinodes.

Named after Ernst Chladni (1756-1827), German physicist; → figure.


Fr.: circardien   

Being, having, characterized by, or occurring in approximately 24-hour periods or cycles, as of biological activity or function (

From L. circa "about," → circum-, + diem, accusative singular of dies "day," → diurnal.

circadian rhythm
  ریتم ِ پیراروزی   
ritm-e pirâruzi

Fr.: rythme circardien   

Any of several physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment. Circadian rhythms are found in most living things, including animals, plants and many tiny microbes.

circadian; → rhythm.

CO ladder
  نردبان ِ CO   
nardebân-e CO

Fr.: échelle CO   

A spectral line energy distribution which plots the intensity of each → carbon monoxide (CO) transition as a function of the upper J number. This type of → diagram is a powerful diagnostic tool, where models show that these CO ladders have very different shapes depending on the type of excitation (i.e. photon dominated region, PDR or X-ray dominated region, XDR) as well as density and radiation environment.

carbon monoxide (CO); → ladder.

co-added image
  وینه‌ی ِ هم‌افزوده، تصویر ِ ~   
vine-ye hamafzudé, tasvir-e ~

Fr.: image intégrée   

An image made up of several individual images of relatively short exposure times which are added together in order to produce a final image of higher quality.

Co-added, from → co- "together" + added p.p. of → add; → image.

Tasvir, → image; hamafzudé from ham- "together", → com-, + afzudé p.p. of afzudan, → add.

compact radio source
  خن ِ رادیویی ِ همپک   
xan-e râdioyi-ye hampak

Fr.: source radio compacte   

An object emitting intense energy in radio wavelength from a small, unresolved central region.

compact; → radio source.

pâdguyi (#)

Fr.: contradiction   

1) The act of contradicting; assertion of the contrary or opposite.
2) Logic: A statement that is false under all circumstances.

M.E., from O.Fr. contradiction or directly from L. contradictionem "objection, counterargument," from contradicere, from contra dicere "to speak against," from → contra- "against" + dicere "to speak," akin to Pers. dis, → form.

Pâdguyi, literally "speaking against," from pâd, → counter-, + guyi, from goftan, → logic.

pâdguyâné (#)

Fr.: contradictoire   

Asserting the contrary or opposite; contradicting; inconsistent; logically opposite (

Adjective from → contradiction.

corotation radius
  شعاع ِ هم‌چرخش   
šoâ'-e ham-carxeš

Fr.: rayon de corotation   

1) In the → X-wind model of → accretion, the distance from the star where the → centrifugal force on a particle corotating with the star balances the → gravitational attraction; in other words, where the → accretion disk rotates at the same → angular velocity as the star.
2) In a → spiral galaxy, the place where the spiral → pattern speed has the same velocity as the → rotation curve of the → galactic disk. In the frame rotating with the wave, particles inside this radius will appear to revolve in the direction of the frame rotation (prograde) while outside this corotation radius, they will be retrograde.

corotation; → radius.

corpuscular radiation
  تابش ِ کرپولی   
tâbeš-e karpuli

Fr.: rayonnement corpusculaire   

A stream of atomic or subatomic particles.

Corpuscular, adj. from → corpuscle; → radiation.

cosmic background radiation
  تابش ِ پس‌زمینه‌ی ِ کیهانی   
tâbeš-e paszaminé-ye keyhâni

Fr.: rayonnement du fond cosmique   

cosmic microwave background radiation (CMBR).

cosmic; → background; → radiation.

cosmic microwave background radiation (CMBR)
  تابشِ ریزموجِ پس‌زمینه‌یِ کیهانی   
tâbeš-e rizmowj-e paszaminé-ye keyhâni

Fr.: rayonnement du fond cosmique microonde   

The diffuse → electromagnetic radiation in the → microwave band, coming from all directions in the sky, which consists of relic photons left over from the very hot, early phase of the → Big Bang. More specifically, the CMBR belong to the → recombination era, when the → Universe was about 380,000 years old and had a temperature of about 3,000 K, or a → redshift of about 1,100. The photons that last scattered at this epoch have now cooled down to a temperature of 2.73 K. They have a pure → blackbody spectrum as they were at → thermal equilibrium before → decoupling. The CMB was discovered serendipitously in 1965 by Penzias and Wilson (ApJ L 142, 419) and was immediately interpreted as a relic radiation of the Big Bang by Dicke et al. (1965, ApJL 142, 383). Such a radiation had been predicted before by Gamow (1948, Nature 162, 680) and by Alpher and Herman (1948, Nature 162, 774). This discovery was a major argument in favor of the Big Bang theory. In 1992, the satellite → Cosmic Background Explorer (COBE) discovered the first anisotropies in the temperature of the CMB with an amplitude of about 30 µK. See also: → cosmic microwave background anisotropy, → dipole anisotropy, → CMB lensing, → CMB angular power spectrum, → acoustic peak, → baryon acoustic oscillation, → WMAP.

cosmic; → microwave; → background; → radiation.

cosmic radio noise
  نوفه‌یِ رادیوییِ کیهانی   
nufe-ye râdioyi-ye keyhâni

Fr.: bruit radio cosmique   

Radio waves emanating from extraterrestrial sources.

cosmic; → radio; → noise.

gahvâré (#)

Fr.: berceau   

1) A bed for a baby that is usually designed to rock back and forth when pushed gently. → Newton's cradle.
2) The place where something begins (

M.E. cradel, from O.E cradol akin to O.H.G. kratto "basket," Ger. Krätze "basket carried on the back;" Pers. gereh "knot;" Skt. granth- "to tie a knot" (Cheung 2007).

Gahvâré "cradle," variants gâhvâré, gowvâré, govâré, from Mid.Pers. gâhwârag "cot, cradle."

cyano radical
  رادیکال ِ سیانو   
râdikâl-e siyâno

Fr.: radical cyano   

A diatomic chemical radical composed of carbon and nitrogen atoms. The triple bonds of C to H leave one electron available, which makes the CN radical very reactive. Organic molecules with the -CN group are potential sources of → prebiotic amino acids. Same as the → CN molecule. The CN radical was first identified by Gay-Lussac, who in 1815 published an extensive study of the derivatives of prussic acid (→ hydrogen cyanide). He showed that the cyano radical remained intact throughout a series of chemical transformations. Also called cyanogen radical.

cyano-; → radical.

cyclic quadrilateral
  چهاربر ِ چرخه‌ای   
cahârbar-e carxe-yi

Fr.: quadrilatère cyclique   

A quadrilateral in which all four vertices lie on the circumference of a circle.

cyclic; → quadrilateral.

cyclotron radius
  شعاع ِ سیکلوترون   
šo'â'-e siklotron

Fr.: rayon de cyclotron   

Same as → Larmor radius.

cyclotron; → radius.

d'Alembert's paradox
  پارادخش ِ دالامبر   
pârâdaxš-e d'Alembert

Fr.: paradoxe de d'Alembert   

A hydrodynamical paradox arising from the neglect of → viscosity in the → steady flow of a fluid around a submerged solid body. According to this paradox, the submerged body would offer no resistance to the flow of an → inviscid fluid and the pressure on the surface of the body would be symmetrically distributed about the body. This paradox may be traced to the neglect of the viscous forces, which are indirectly responsible for fluid resistance by modifying the velocity field close to a solid body (Meteorology Glossary, American Meteorological Society).

d'Alembert's principle; → paradox.

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.

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