Fr.: extinction atmosphérique
The decrease in the intensity of light from a celestial body due to absorption and scattering by Earth's atmosphere. It increases from the zenith to the horizon and affects short wavelengths more than long wavelengths, so that objects near the horizon appear redder than they do at the zenith.
Cretaceous-Paleogene extinction event
ruydâd-e xâmuši-ye Gacâsâ-Pârinzâd
Fr.: extinction Crétacé-Tertiaire
The → mass extinction event that destroyed the dinosaurs and a majority of other species on Earth approximately 65 million years ago. This event is believed to have been the impact of a 10 km-size → asteroid or → comet nucleus and its aftereffects, including a severe → impact winter. The collision would have released the energy equivalent to 100 million megatonnes (teratonnes) of → TNT, i.e. more than 109 times the energy of the atomic bomb dropped on Hiroshima on August 6, 1945. Same as the → Cretaceous-Tertiary event.
1) Dimming of light by an intervening medium (the Earth's atmosphere or the interstellar medium).
It is usually due to both scattering and absorption.
Noun of extinct, from L. extinctus, p.p. of extinguere "to quench, wipe out," from → ex- "out" + stinguere "to quench," from PIE base *steig- "to prick, stick, pierce;" cf. Mod.Pers. tiz, tež, tig, tej, tij, tiq "sharp;" Av. tiγra- "pointed," tiγray- "arrow;" → deblur.
Xâmuši, noun of xâmuš "extinguished; silent," Mid.Pers. xâmôš "silent;" cf. Skt. amrs- "to bear patiently."
Fr.: coefficient d'extinction
Gradient of apparent magnitude with air mass.
Fr.: correction d'extinction
In → photometric calibration, the correction for energy loss undergone by radiation due to the → atmospheric extinction. Extinction correction is done using → standard stars observed at different → airmasses.
Fr.: courbe de l'extinction interstellaire
A graph representing the variation of the → interstellar extinction against → wavelength. Usually it displays the → normalized values of extinction as a function of (the → inverse) of the wavelength (in → microns). See, e.g., Sandage & Mathis, 1979, Ann. Rev. Astron. Astrophys. 17, 73.
Fr.: étoiles d'extinction
Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.
Fr.: extinction interstellaire
The dimming of light traveling in the interstellar space due to the combined effects of absorption and scattering by interstellar dust particles. Interstellar extinction increases at shorter (bluer) wavelengths, resulting in → interstellar reddening.
Fr.: extinction logarithmique
Same as → reddening coefficient.
Fr.: extinction en masse
An event in the history of life on Earth in which large numbers of species (sometimes more than 90% of some species) vanish in a relatively short period of time. In spite of controversy, it is generally recognized that there have been at least six major mass extinctions. These occurred in the late Cambrian (500 million years ago), in the late Ordovician (440 million years ago), in the late Devonian (365 million years ago), at the end of the Permian (245 million years ago), in the late Triassic (208 million years ago), and at the end of the Cretaceous (65 million years ago).
Fr.: extinction visuelle
The → extinction in the visual range of the electromagnetic radiation.