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: 3 Search : ultraluminous
ultraluminous
  اولتر-تابان   
ultar-tâbân

Fr.: ultralumineux   

The quality of an object whose → luminosity exceeds a certain value.

ultra-; → luminous.

ultraluminous infrared galaxy (ULIRG)
  کهکشانِ فروسرخ ِ اولتر-تابان   
kahkešân-e forusorx-e ultar-tâbân

Fr.: galaxie ultralumineuse en infrarouge   

A galaxy that emits more than 90% of its energy in the infrared (8-1000 µm) and whose infrared luminosity exceeds 1012 solar luminosities. → luminous infrared galaxy (LIRG). Quasars can also have such high or even higher bolometric luminosities. However LIRGs and ULIRGs emit the bulk of their energy in the infrared. Most of ULIRGs are found in merging and interacting galaxy systems. It is thought that their luminosity results from galactic collisions, which increase the rate of star formation.

ultraluminous; → infrared; → galaxy.

ultraluminous X-ray source (ULX)
  خن ِ پرتو ِ ایکس ِ اولتر-تابان   
xan-e partow-e iks-e ultar-tâbân

Fr.: source ultralumineuse en rayons X   

An X-ray source that is not in the nucleus of a galaxy, and is more luminous than 1039 ergs s-1, brighter than the → Eddington luminosity of a 10 → solar mass → black hole. In general, there is about one ULX per galaxy in galaxies which host ULXs. The Milky Way contains no such objects. ULXs are thought to be powered by → accretion onto a → compact object. Possible explanations include accretion onto → neutron stars with strong → magnetic fields, onto → stellar black holes (of up to 20 → solar masses) at or in excess of the classical Eddington limit, or onto → intermediate-mass black holes (103-105 solar masses). NGC 1313X-1, NGC 5408X-1, and NGC 6946X-1 are three ULXs with X-ray luminosities up to ~ 1040 erg s-1 (Ciro Pinto et al., 2016, Nature 533, N) 7601).

ultraluminous; → X-ray source.