An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < R a rad rad rad rad rad rad ran rap ray rea rea rec rec Red red ref ref reg rel rel rel rep res res res res rev Rho Rie ril riv rol Ros rot rul > >>

Number of Results: 717
Rosseland mean opacity
  کدری ِ میانگین ِ روسلاند   
kederi-ye miyângin-e Rosseland

Fr.: opacité moyenne de Rosseland   

The → opacity of a gas of given composition, temperature, and density averaged over the various wavelengths of the radiation being absorbed and scattered. The radiation is assumed to be in → thermal equilibrium with the gas, and hence have a → blackbody spectrum. Since → monochromatic opacity in stellar plasma has a complex frequency dependence, the Rosseland mean opacity facilitates the analysis. Denoted κR, it is defined by: 1/κR = (π/4σT3) ∫(1/kν) (∂B/∂T)νdν, summed from 0 to ∞, where σ is the → Stefan-Boltzmann constant, T temperature, B(T,ν) the → Planck function, and kν monochromatic opacity (See Rogers, F.J., Iglesias, C. A. Radiative atomic Rosseland mean opacity tables, 1992, ApJS 79, 507).

Named after Svein Rosseland (1894-1985), a Norwegian astrophysicist, who obtained the expression in 1924; → mean; → opacity.

Rossiter-McLaughlin effect
  اُسکر ِ راسیتر-مک‌لاکلین   
oskar-e Rossiter-McLaughlin

Fr.: effet Rossiter-McLaughlin   

A → spectroscopic phenomenon observed when either an → eclipsing binary's → secondary star or an → extrasolar planet is seen to → transit across the face of the → primary body. Because of the rotation of the star, an asymmetric distortion takes place in the → line profiles of the stellar spectrum, which changes during the transit. The measurement of this effect can be used to derive the → alignment of the → orbit of the transiting exoplanet with respect to the → rotation axis of the star.

Named after Richard Alfred Rossiter (1886-1977) and Dean Benjamin McLaughlin (1901-1965), American astronomers.

carxidan (#)

Fr.: tourner   

To turn around an axis. See also → revolve.

From L. rotare "to cause to spin, roll, move in a circle," from L. rota "wheel;" cognate with Pers. râh "way, path" (from Mid.Pers. râh, râs "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE *roto- "to run, to turn, to roll").

Carxidan "to rotate," from carx "every thing performing a circulatory motion; a wheel; a cart;" Mid.Pers. chr "wheel," Parthian cxr "wheel;" Ossetic calx "wheel;" Av. caxra- "wheel;" cognate with Skt. cakra- "wheel, circle; cycle," carati "he moves, wanders;" Gk. kyklos "circle, wheel," polos "axis of a sphere," polein "move around;" L. colere "to dwell in, to cultivate, move around," colonus "farmer, settler;" O.E. hweol "wheel;" Rus. koleso "wheel."

  چرخنده، چرخان   
carxandé, carxân

Fr.: en rotation   

Capable of or having rotation.

From → rotate + → -ing.

rotating black hole
  سیه‌چال ِ چرخان   
siyahcâl-e carxân

Fr.: trou noir en rotation   

A black hole that possesses angular momentum, as first postulated by Roy C. Kerr in 1963. Opposite of a stationary black hole. → ergosphere.

rotating; → black hole.

rotating star
  ستاره‌ی ِ چرخان، ~ چرخنده   
setâre-ye carxân, ~ carxandé

Fr.: étoile en rotation   

A star that has a non-zero → angular velocity. In a rotating star, the → centrifugal forces reduce the → effective gravity according to the latitude and also introduce deviations from sphericity. In a rotating star, the equations of stellar structure need to be modified. The usual spherical coordinates must be replaced by new coordinates characterizing the → equipotentials. See also → von Zeipel theorem.

rotating; → star.

carxeš (#)

Fr.: rotation   

The motion of a body about its axis.

Verbal noun of → rotate.

rotation axis
  آسه‌ی ِ چرخش   
âse-ye carxeš

Fr.: axe de rotation   

The imaginary line around which an object rotates. Same as → rotational axis and → axis of rotation.

rotation; → axis.

rotation curve
  خم ِ چرخش   
xam-e carxeš

Fr.: courbe de rotation   

A plot of the variation in → orbital velocity of stars and → interstellar matter with distance from the center of a → galaxy. A "flat" rotation curve indicates that the mass of the galaxy increases linearly with distance from its center. See also: farsi→ Keplerian rotation curve

Rotation; → curve.

rotation energy
  کاروژ ِ چرخش   
kâruž-e carxeš

Fr.: énergie de rotation   

The → kinetic energy of rotational motion of an object. It is expressed by ER = (1/2)Iω2, where I is the → moment of inertia and ω → angular velocity (2π/P).

rotation; → energy.

rotation frequency
  بسامد ِ چرخش   
basâmad-e carxeš

Fr.: fréquence de rotation   

1) The number of rotations per unit time of a rotating object.
2) The number of → stellar rotations per unit time. The reciprocal of the → rotation period. This parameter usually refers to the equator of the star, because stars do not rotate as solid bodies.

rotation; → frequency.

rotation period
  دوره‌ی ِ چرخش   
dowre-ye carxeš (#)

Fr.: période de rotation   

The interval of time during which an object turns once about its axis.

rotation; → period.

rotation phase
  فاز ِ چرخش   
fâz-e carxeš

Fr.: phase de rotation   

A position parameter used in → stellar magnetic field studies. Its zero value represents the moment when, during → stellar rotation, the positive → magnetic pole is nearest to the → line of sight.

rotation; → phase.

rotation-induced turbulence
  آشوبناکی ِ زاییده‌ی ِ چرخش، ~ درهازیده از ~   
âšubnâki-ye zâyide-ye carxeš, darhâzidé az ~

Fr.: turbulence induite par turbulence   

A type of → turbulence with motions more vigorous in the horizontal than in the vertical direction occurring in internal radiation zone of → rotating stars. Same as → shear turbulence.

rotation; → induced; → turbulence.

rotation-powered pulsar (RPP)
  تپار ِ چرخش-توان، پولسار ِ ~ ~   
tapâr-e carxeš-tavân, pulsâr-e ~ ~


A → neutron star that is spinning down as a result of → torques from → magnetic dipole radiation and particle emission. RPPs derive their energy primarily from the → rotation of the neutron star. The energy from their → spin-down appears as broad-band pulsations from → radio to → gamma-ray wavelengths and as a → wind of energetic particles flowing into their surrounding → pulsar wind nebulae. Since the discovery of RPPs through their radio → pulsations in 1967, more than 2000 → radio pulsars are now known with periods ranging from a few milliseconds to several seconds (A. K. Harding, 2013, Front. Phys. 8, 679).

rotation; → power; → pulsar.

rotation-vibration spectrum
  بیناب ِ چرخش-شیوش   
binâb-e carxeš-šiveš

Fr.: spectre rotation-vibration   

The spectrum of a molecule resulting from the simultaneous rotation and vibration of its constituent atoms.

rotation; → vibration; → spectrum.

carxeši (#)

Fr.: rotationnel   

Of or pertaining to → rotation.

Rotational, adj., from → rotation + → -al.

rotational angular momentum
  جنباک ِ زاویه‌ای ِ چرخشی   
jonbâk-e zâviyeyi-ye carxeši

Fr.: moment angulaire rotationnel, moment cinétique ~   

The → angular momentum of a body rotating about an axis. The rotational angular momentum of a solid homogeneous sphere of mass M and radius R rotating about an axis passing through its center with a period of T is given by: L = 4πMR2/5T.

rotational; → angular; → momentum.

rotational axis
  آسه‌ی ِ چرخش   
âse-ye carxeš

Fr.: axe de rotation   

An imaginary line about which a solid object rotates. Same as → rotation axis and → axis of rotation.

rotational; → axis.

rotational broadening
  پهنش ِ چرخشی   
pahneš-e carxeši

Fr.: élargissement rotationnel   

The spectral line broadening caused by stellar rotation. Light from two rims of the star will be Doppler shifted in opposite directions, resulting in a line broadening effect. The line broadening depends on the inclination of the star's pole to the line of sight. The derived value is a function of ve. sini, where ve is the rotational velocity at the equator and i is the inclination, which is not always known. The fractional width (Δλ/λ) is of the order of 10-3 for B stars.

rotational; → broadening.

<< < R a rad rad rad rad rad rad ran rap ray rea rea rec rec Red red ref ref reg rel rel rel rep res res res res rev Rho Rie ril riv rol Ros rot rul > >>