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Fr.: anneau A
One of → Saturn's rings, lying beyond the → B ring at 122,170 km from the center of Saturn, with a width of 14,600 km.
Fr.: diffusion atmosphérique
The → scattering of → electromagnetic radiation by various particles in the Earth's → atmosphere. The phenomenon is caused by collisions between photons and several scattering agents such as atoms, molecules, → aerosols, and water droplets in clouds. → Rayleigh scattering.
→ atmospheric; → scattering.
Fr.: anneau B
One of → Saturn's rings, lying beyond the → C ring and before the → A ring, extending from 92,000 to 117,300 km (width 25,300 km) from the center of Saturn. The B ring is bounded by the → Huygens Division.
Scattering of radiation or particles through angles greater than 90° with respect to the original direction of motion.
Fr.: cratère Barringer
Same as → Meteor Crater.
Names after Daniel Barringer (1860-1929), American geologist, who bought the Crater in 1903, convinced that it was made by a huge → meteorite; → crater.
A property of some crystalline materials (e.g. calcite, quartz) which have different indices of refraction associated with different crystallographic directions. Therefore, the crystal splits incident transmitted light into two beams, each polarized perpendicularly to the other. Also called double refraction.
Birefringence, from → bi- + refringence, from L. refringere "to break up," from → re- "back" + combination form of frangere "to break."
Došekast, from do- "two," → bi- + šekast "breaking," from šekastan "to break up," Mid.Pers. škastan, Av. skand- "to break."
došekastgar, došekasti (#)
Of or relating to → birefringence.
pâlâye-ye došekastgar, ~ došekasti
Fr.: filtre biréfringent
A type of narrow-band filter that uses the birefringence to produce selective absorption of polarized light.
→ birefringent; → filter.
Fr.: vide biréfringent
Empty space undergoing → vacuum birefringence.
→ birefringent; → vacuum.
Fr.: corde noire
The extension of the → black hole concept in a → space-time with → dimensions higher than 4. Theoretically, it is possible to extend the 4D black hole with S2 horizon into the fifth dimension producing a hypercylindrical black hole S2× R. Black strings are unstable; it is not yet well understood whether they end up as black holes or different objects.
In → galactic dynamics models, the → scattering of stars at radii substantially away from → corotation resonance, especially at the → Lindblad resonances, leading to a higher → eccentricity. The → spiral wave response of a → galactic disk to a co-orbiting mass → clump blurs the distinction between scattering by → spiral arms and by mass clumps. See also → churning (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).
Verbal noun of → blur.
Fr.: diffusion de Brillouin
Scattering of electromagnetic waves in solids and liquids when, as a result of the scattering process, an acoustic → phonon is emitted or absorbed. Brillouin scattering is analogous to → Raman scattering.
→ Brillouin zone; → scattering.
Fr.: anneau C
One of → Saturn's rings, lying beyond the → D ring and before the → B ring, at 74,658 km from the center of Saturn, with a width of 17,500 km. Same as the → Crepe ring.
Fr.: rotation de Carrington
A system for counting rotations of the Sun based on the mean → synodic rotation period of the Sun. Initially, Lord Carrington determined the solar rotation rate by watching low-latitude → sunspots. He defined a fixed solar coordinate system that rotates in a sidereal frame exactly once every 25.38 days. This means that the solar rotation period, as viewed from the Earth, is assumed to be constant. However, the synodic rotation rate varies during the year because of the changing speed of the Earth in its orbit and the mean synodic period is about 27.2753 days. Carrington rotation number 1 began on November 9, 1853.
Named for Richard C. Harrington (1826-1875), British astronomer, who initiated the system; → rotation.
Fr.: agglomération, groupement
Grouping of a number of similar astronomical objects.
Noun from verb → cluster.
qânun-e xušé bandi
Fr.: loi de groupement
An empirical power-law representing the number of stellar clusters as a function of the number of stars per cluster within an interval. It is expressed as: N(N*) dN*∝ N*-α dN*, where N(N*) is the number of clusters containing N* stars and dN* is the interval in star number. It is believed that this relationship applies to a variety of systems, including stellar clusters, globular clusters, H II regions (Oey et al. 2004, AJ 127, 1632).
→ clustering; → law.
Fr.: diffusion cohérente
A scattering process in which the scattered radiation bears the same frequency and phase as the incident radiation.
→ coherent; → scattering.
parâkaneš-e Compton (#)
Fr.: diffusion Compton
Scattering of a → photon due to the → Compton effect.
→ Compton; → scattering.
Same as → Abbe number.
Noun from → constrain.
Fr.: corde cosmique
A hypothetical → cosmic defect predicted to be infinitesimally small in cross section but enormously long and massive. Cosmic strings should not be confounded with → subatomic strings predicted by → string theory.
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