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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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quartic equation
  هموگش ِ چارُمیک   
hamugeš-e câromik

Fr.: équation quartique   

An equation containing unknowns of the fourth power; the general form: ax4 + bx3 + cx2 + dx + e = 0.

From L. quart(us) "fourth" (→ quarter) + → -ic; → equation.

hamugeš, → equation; câromân, from cârom "fourth," from câr, cahâr "four" + -om "-th" + -ik, → -ic.

quasi-single-scattering approximation
  نزدینش ِ چونان-تک‌پراکنش   
nazdineš-e cunân-tak-parâkaneš

Fr.:   

A model of radiative transfer that ignores forward scattering of photons; assuming forward-scattered light as un-scattered.

quasi-; → single; → scattering; → approximation.

quasiperiodic motion
  جنبش ِ چونان-دوره‌ای   
jonbeš-e cunân-dowreyi

Fr.: mouvement quasipériodique   

In a dynamical system, a form of motion that is regular but never exactly repeating. Quasiperiodic motion appears when the system contains two or more incommensurate frequencies.

quasi-; → periodic; → motion.

quintic equation
  هموگش ِ پنجمیک   
hamugeš-e panjomik

Fr.: équation quintique   

An equation containing unknowns of the fifth power.

quintic; → equation.

R association
  آهزش ِ R   
âhazeš-e R

Fr.: association R   

A → stellar association containing a number of → reflection nebulae. The stars are of low or intermediate mass and young, less than a million years old. They are still surrounded by patches of dust that reflect and absorb light from the interstellar cloud in which they formed. This type of association was first suggested by Sidney van den Bergh (1966, AJ 71, 900).

R, from → reflection; → association.

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

Fr.: front d'ionisation de type R   

A spherical → ionization front of → H II regions that moves radially outward from the → exciting star at a velocity much higher than → sound speed in the surrounding cold neutral gas of uniform density (ahead of the front). R-type ionization fronts corresponds to early evolution of H II regions, and will eventually transform into → D-type ionization fronts. If the motion of the front is supersonic relative to the gas behind as well as ahead of the front, the front is referred to as weak R. The strong R front correspond to a large density increase across the front.

R referring to a rarefied gas; → type; → ionization; → front.

radial migration
  کوچ ِ شعاعی   
kuc-e šo'â'i

Fr.: migration radiale   

The process whereby a → disk star changes its → galactocentric distance. Radial migration involves → angular momentum transfer, resulting from → resonances created by transient → density waves such as → bars or → spiral arms in → galactic disks. According to → galactic dynamics models, → churning is the main cause of radial migration. Radial migration of stars plays an important role in shaping the properties of galactic disks.

radial; → migration.

radial motion
  جنبش ِ شعاعی   
jonbeš-e šo'â'i

Fr.: mouvement radial   

A motion away from or toward a central point or axis.

radial; → motion.

radiation
  تابش   
tâbeš (#)

Fr.: radiation, rayonnement   

The emission of any → rays, → waves, or → particles from a source; usually applied to the → emission of → electromagnetic energy.

Verbal noun of → radiate.

radiation belt
  کمربند ِ تابش، ~ تابشی   
kamarband-e tâbeš (#), ~ tâbeši (#)

Fr.: ceinture de radiations   

A ring-shaped region in the → magnetosphere of a planet in which charged particles are trapped by the planet's magnetic field. The radiation belts surrounding Earth are known as the → Van Allen belts.

radiation; → belt.

radiation constant
  پایای ِ تابش   
pâypa-ye tâbeš

Fr.: constante de rayonnement   

Same as → radiation density constant.

radiation; → constant.

radiation damping
  میرایی ِ تابشی   
mirâyi-e tâbeši

Fr.: amortissement par rayonnement   

Damping of a system which loses energy by → electromagnetic radiation.

radiation; → damping.

radiation density constant
  پایای ِ چگالی ِ تابش   
pâypa-ye cagâli-ye tâbeš

Fr.: constante de rayonnement   

The constant related to the total energy radiated by a → blackbody and defined as: a = 4σ/c, where σ is the → Stefan-Boltzmann constant and c the → speed of light. Its value is a = 7.5657 x 10-15 erg cm-3 K-4. Same as → radiation constant.

radiation; → density; → constant.

radiation era
  دوران ِ تابش   
dowrân-e tâbeš

Fr.: ère du rayonnement   

The epoch in the history of the Universe, lasting from the → Big Bang until about 400,000 years later, when the temperature had dropped to 109 K and the rate of electron-positron → pair annihilation exceeded the rate of their production, leaving radiation the dominant constituent of the Universe. The radiation era was followed by the → matter era.

radiation; → era.

radiation field
  میدان ِ تابش   
meydân-e tâbeš

Fr.: champ de rayonnement   

1) The portion of an → electromagnetic field outside the → induction field where there is a power flow of both → magnetic and → electric components in a well-defined relationship.
2) → interstellar radiation field

radiation; → field.

radiation length
  درازای ِ تابش   
derâzâ-ye tâbeš

Fr.: longueur de rayonnement   

The mean distance traveled by a photon or particle in a given medium before its energy is reduced by a factor e due to its interaction with matter.

radiation; → length.

radiation pattern
  الگو‌ی ِ تابش   
olgu-ye tâbeš

Fr.: diagramme de rayonnement   

Same as → antenna pattern.

radiation; → pattern.

radiation pressure
  فشار ِ تابش   
fešâr-e tâbeš

Fr.: pression de radiation   

The → momentum carried by → photons to a surface exposed to → electromagnetic radiation. Stellar radiation pressure on big and massive objects is insignificant, but it has considerable effects on → gas and → dust particles. Radiation pressure is particularly important for → massive stars. See, for example, → Eddington limit, → radiation-driven wind , and → radiation-driven implosion. The → solar radiation pressure is also at the origin of various physical phenomena, e.g. → gas tails in → comets and → Poynting-Robertson effect.

radiation; → pressure.

radiation sickness
  بیماری ِ تابشی   
bimâri-ye tâbeši

Fr.: mal des rayons   

An illness resulting from excessive exposure to ionizing radiation. The earliest symptoms are nausea, vomiting, and diarrhea, which may be followed by loss of hair, hemorrhage, inflammation of the mouth and throat, and general loss of energy.

radiation; sickness, M.E. siknesse, seknesse; O.E. sēocnesse, from seoc + suffix -ness.

Bimâri "sickness, infirmity, disease," from bimâr "sick, infirm, afflicted;" Mid.Pers. vêmâr "sick, ill;" maybe by corruption of Proto-Iranian *amavayā-bara- "bearing illness;" cf. Av. amavayā- "pain, suffering, affliction;" Skt. ámīvā- "pain, grief, distress" + *bara- "bearing;" cf. Av. bar- "to bear, carry;" Mod.Pers. bar-, bordan "to bear, carry, lead." Alternatively, from *vi-mar-, prefixed *mar- "to die;" cf. Av. mar- "to die;" Mod.Pers. mir-, mordan "to die;" Skt. mar- "to die;" cognate with Gk. emorten "died;" L. morior "to die;" tâbeši related to tâbeš, → radiation.

radiation spectrum
  بیناب ِ تابش   
binâb-e tâbeš

Fr.: spectre de rayonnement   

The components of radiation arranged in order of their wavelengths, frequencies, or quantum energies. For particle radiation they are arranged in order of their kinetic energies.

radiation; → spectrum.

<< < "no abe acc act aff ama ani ant aps ast atm aut bar bic Boh bou cal car cel che cla col com com Com con con con con con con con con con con con con Cor cor cot cul de- dec dem des dif dil dir dis dom dyn Edd ele ele emi equ Eve exc exp fac fin for fre fuz gen Glo gra gra Ham hel hor hyd ign inc inf Inf int Int int ion irr jum Lag lea lig lin Lor Lyo mag mat met min Mon moo NaC neg New New non non non nul obs one opt Ori oxi par per per phl pho pla Pla pol pos pre pro pro pse qua rad rad rea rec reg rel res ret rot Ryd sci sec sec sep sim Soc son spe sta Ste Sto sub sup syn the Tho top tra Tro unc vec vio Was Wil Zhe > >>