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brown dwarf

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brown dwarf

A theoretical ‘star’ formed by the contraction of a lump of gas with a mass too small for nuclear reactions to begin in the core. This limit on stellar mass is uncertain but is thought to be about 0.08 solar masses. An object below this limit will shine for only 100 million years as a result of gravitational contraction on the Hayashi track, and then cool off. Its interior consists of degenerate matter. Some of the least luminous red dwarf stars may actually be brown dwarfs. The first brown dwarf, named Gliese 229B, was unambiguously identified in 1995 with the Palomor 60-inch telescope. It orbits the red-dwarf star Gliese 229A. The presence of methane lines in its spectrum is believed to be a unique signature of a brown dwarf, which can be used to distinguish it from a very low-mass star. Since 1995 numerous other brown-dwarf candidates have been found.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

brown dwarf

[¦braün ¦dwȯrf]
(astronomy)
A starlike body whose mass is too small (less than about 8% that of the sun) to sustain nuclear reactions in its core. Also known as black dwarf; failed star; infrared dwarf; lilliputian star; substellar object; super-Jupiter.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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References in periodicals archive
Since the GPIES survey began five years ago, the team has imaged six planets and three brown dwarfs orbiting these 300 stars.
For this reason, brown dwarfs are often called failed stars, but despite its miniature proportions, EBLM J055557Ab maintains just enough mass to enable the fusion of hydrogen into helium in its core.
This process has succeeded in removing approximately 90% of the small star's mass, forcing it to experience a sea change from a true star into a sub-stellar brown dwarf.
Researchers found the aurora- similar to the famous Northern Lights on Earth- not from a planet, but from a low-mass star at the boundary between stars and brown dwarfs, Science Daily reported.
A brown dwarf, or "failed star", is an object more massive than a planet yet too small to trigger the thermonuclear reactions that power stars.
The newfound coldest brown dwarf is named WISE J085510.83-071442.5.
There are many candidates for dark matter, including undetected brown dwarf stars, white dwarf stars, black holes, or neutrinos with mass (a neutrino is a fundamental nuclear particle that is electrically neutral and of much smaller mass, if any at all, than an electron).
Only a few examples of such close brown dwarf binaries are known and this is only the second example of AO spectroscopic observations, the NAOJ officials said.
Since it wasn't totally cold, it was called a brown dwarf. The existence of this particular brown dwarf was later disputed, but other examples were reported.
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