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rotating black hole 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 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. |
rotation carxeš (#) Fr.: rotation The motion of a body about its axis. Verbal noun of → rotate. |
rotation axis âse-ye carxeš Fr.: axe de rotation The imaginary line around which an object rotates. Same as → rotational axis and → axis of rotation. |
rotation curve 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 kâruž-e carxeš Fr.: énergie de rotation The → kinetic energy of rotational motion of an object. It is expressed by E_{R} = (1/2)Iω^{2}, where I is the → moment of inertia and ω → angular velocity (2π/P). |
rotation frequency basâmad-e carxeš Fr.: fréquence de rotation 1) The number of rotations per unit time of a rotating object. |
rotation period dowre-ye carxeš (#) Fr.: période de rotation The interval of time during which an object turns once about its axis. |
rotation phase 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-induced turbulence 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) tapâr-e carxeš-tavân, pulsâr-e ~ ~ Fr.: 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-vibration spectrum binâb-e carxeš-šiveš Fr.: spectre rotation-vibration The spectrum of a molecule resulting from the simultaneous rotation and vibration of its constituent atoms. |
rotational carxeši (#) Fr.: rotationnel Of or pertaining to → rotation. |
rotational angular momentum 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 = 4πMR^{2}/5T. → rotational; → angular; → momentum. |
rotational axis 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 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 v_{e}. sini, where v_{e} 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. |
rotational Eddington limit hadd-e Eddington-e carxeši Fr.: limite d'Eddington avec rotation The → Eddington limit of luminosity for a → rotating star in which both the effects of → radiative acceleration and rotation are important. Such objects mainly include → OB stars, → LBV, → supergiants, and → Wolf-Rayet stars. It turns out that the maximum permitted luminosity of a star is reduced by rotation, with respect to the usual Eddington limit (Maeder & Meynet, 2000, A&A, 361, 159). → rotational; → Eddington limit. |
rotational energy kâruš-e carxeši Fr.: énergie rotationnelle The → kinetic energy due to the → rotation of and object. Rotational energy is part of the total kinetic energy of the body. It is given by: (1/2)Iω^{2}, where I is the → moment of inertia and ω is the → angular velocity. Same as → angular kinetic energy. → rotational; → energy. |
rotational mixing âmizeš-e carxeši Fr.: mélange rotationnel A consequence of → stellar rotation that deforms the star, triggers instabilities (→ shear turbulence and → meridional currents) leading to → transport of chemical species in the star. The efficiency of rotational mixing (measured for instance by the degree of surface → enrichments at a given → evolutionary stage) increases when the initial mass and rotation increase. This efficiency increases also when the initial → metallicity decreases. This is due to the fact that when the metallicity is lower, the stars are more compact. This makes the → gradients of the → angular velocity steeper in the stellar interiors. Steeper gradients produce stronger shear turbulence and thus more mixing. Rotational mixing can bring to the surface heavy elements newly synthesized in the stellar core. Rotation thus produces an increase of the → opacity of the outer layers and activates strong → mass loss through → radiatively driven winds. This effect may be responsible for the loss of large fractions of the initial mass of the star (Meynet et al. 2007, arXiv:0709.2275). → rotational; → mixing. |
rotational modulation (ROT) degarâhangeš-e carxeši Fr.: modulation rotationnelle A very small variation in the surface brightness of a single star due to its rotation. Several types of stars are known to have photospheric spots. Brightness variation occurs as rotation carries star spots or other localized activity across the line of sight. → rotational; → modulation. |
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