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Brown dwarf is a substellar object that occupies the mass range between the heaviest gas giant planets and the lightest stars, having masses between approximately 13 to 75–80 times that of Jupiter (MJ), or approximately 2.5×1028 kg to about 1.5×1029 kg. Below this range are the sub-brown dwarfs, and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.
Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H) and to fuse lithium (7Li) if their mass is above a debated threshold of 13 MJ and 65 MJ, respectively. It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their supposed nuclear fusion reactions.
Stars are categorized by spectral class, with brown dwarfs designated as types M, L, T, and Y.[ Despite their name, brown dwarfs are of different colors. Many brown dwarfs would likely appear magenta to the human eye, or possibly orange/red. Brown dwarfs are not very luminous at visible wavelengths.
There are planets known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.
At a distance of about 6.5 light years, the nearest known brown dwarf is Luhman 16, a binary system of brown dwarfs discovered in 2013. HR 2562 b is listed as the most-massive known exoplanet (as of December 2017) in NASA’s exoplanet archive, despite having a mass (30±15 MJ) more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs. — Wikipedia
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Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
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Fossil of smallest Old World monkey species...
on July 15, 2019 at 11:21 am
Researchers from the National Museums of Kenya, University of Arkansas, University of Missouri and Duke University have announced the discovery of a tiny monkey that lived in Kenya 4.2 million years ago.
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Ultra-short period brown dwarf discovered
on June 27, 2019 at 1:10 pm
An international team of astronomers has detected a new brown dwarf with an ultra-short orbital period that transits an active M-dwarf star. The newfound object, designated NGTS-7Ab, turns out to be the shortest period transiting brown dwarf around a main or pre-main sequence star discovered to date. The finding is detailed in a paper published June 19 on the arXiv pre-print server.
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Massive brown dwarf detected by astronomers
on June 20, 2019 at 1:00 pm
An international team of astronomers has found a new brown dwarf, one of the most massive objects of this type discovered to date. The newly detected brown dwarf, designated EPIC 212036875 b, turns out to be about 50 times more massive than Jupiter. The finding is detailed in a paper published June 13 on arXiv.org.
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The satellite with X-ray vision
on June 19, 2019 at 11:35 am
In the early hours of October 23, 2011, ROSAT was engulfed in the waves of the Indian Ocean. This was the end of a success story that is unparalleled in German space exploration research. The satellite, developed and built by a team led by Joachim Trümper from the Garchingbased Max Planck Institute for Extraterrestrial Physics, not only found more than 150,000 new cosmic X-ray sources, it also revolutionized astronomy.
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Another brown dwarf in the system? Study...
on June 18, 2019 at 1:00 pm
Aiming to constrain the orbit and dynamical mass of the brown dwarf in the HD 206893 system, an international team of astronomers has investigated the host star and its companion using a combination of observing techniques. Results of this observational campaign suggest the presence of another massive object in the system, most likely a brown dwarf. The findings are detailed in a paper published June 7 on arXiv.org.