An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 11 Search : extinction
atmospheric extinction
  خاموشی ِ جوی   
xâmuši-ye javvi

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.

atmospheric; → extinction.

Cretaceous-Paleogene extinction event
  رویداد ِ خاموشی ِ گچاسا-پارینزاد   
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.

Cretaceous; → Paleogene; → extinction; → event.

extinction
  خاموشی   
xâmuši (#)

Fr.: extinction   

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.
2) Paleontology: The act or process of dying out or coming to an end, becoming extinct: the extinction of a species; → mass extinction.

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."

extinction coefficient
  همگر ِ خاموشی   
hamgar-e xâmuši

Fr.: coefficient d'extinction   

Gradient of apparent magnitude with air mass.

extinction; → coefficient.

extinction correction
  ارشایش ِ خاموشی   
aršâyeš-e xâmuši

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.

extinction; → correction.

extinction curve
  خم ِ خاموشی   
xam-e xâmuši

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.

extinction; → curve.

extinction stars
  ستارگان ِ خاموشی   
setâregân-e xâmuši

Fr.: étoiles d'extinction   

Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.

extinction; → star.

interstellar extinction
  خاموشی ِ اندر-اختری   
xâmuši-ye andaraxtari

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.

interstellar; → extinction.

logarithmic extinction
  خاموشی ِ لگاریتمی   
xâmuši-ye logâritmi

Fr.: extinction logarithmique   

Same as → reddening coefficient.

logarithmic; → extinction.

mass extinction
  خاموشی ِ انبوه   
xâmuši-ye anbuh

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).

mass; → extinction.

visual extinction
  خاموشی ِ دیدگانی   
xâmuši-ye didgâni

Fr.: extinction visuelle   

The → extinction in the visual range of the electromagnetic radiation.

visual; → extinction