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Brown dwarfs are substellar objects not massive enough to sustain hydrogen-1 fusion reactions in their cores, unlike main-sequence stars. They occupy the mass range between the heaviest gas giants and the lightest stars, with an upper limit around 75<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> to 80 Jupiter masses (MJ). Brown dwarfs heavier than about 13 MJ are thought to fuse deuterium and those above ~65 MJ, fuse lithium as well.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The defining differences between a very-low-mass brown dwarf and a gas giant (~13 MJ) are debated.<ref name=ab>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> One school of thought is based on formation; the other, on the physics of the interior.<ref name=ab/> Part of the debate concerns whether "brown dwarfs" must, by definition, have experienced fusion at some point in their history.

Stars are categorized by spectral class, with brown dwarfs being designated as types M, L, T, and Y.<ref name="ab" /><ref name="MichaelCushing2014">{{#invoke:citation/CS1|citation |CitationClass=citation }}</ref> Despite their name, brown dwarfs are of different colors.<ref name="ab" /> Many brown dwarfs would likely appear magenta to the human eye,<ref name="ab" /><ref name=Burrows2001>{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> or possibly orange/red.<ref name="Cain">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Brown dwarfs are not very luminous at visible wavelengths.

Some planets are 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. DENIS-P J082303.1-491201 b is listed as the most-massive known exoplanet (as of March 2014) in NASA's exoplanet archive, despite having a mass ({{safesubst:#invoke:val|main}} MJ) more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs.<ref>[1]</ref>


Brown dwarf sections
Intro  History  Theory  Observations  Planets around brown dwarfs  Superlative brown dwarfs  See also  References  External links  

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{{#invoke:Multiple image|render}}

Brown dwarfs are substellar objects not massive enough to sustain hydrogen-1 fusion reactions in their cores, unlike main-sequence stars. They occupy the mass range between the heaviest gas giants and the lightest stars, with an upper limit around 75<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> to 80 Jupiter masses (MJ). Brown dwarfs heavier than about 13 MJ are thought to fuse deuterium and those above ~65 MJ, fuse lithium as well.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The defining differences between a very-low-mass brown dwarf and a gas giant (~13 MJ) are debated.<ref name=ab>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> One school of thought is based on formation; the other, on the physics of the interior.<ref name=ab/> Part of the debate concerns whether "brown dwarfs" must, by definition, have experienced fusion at some point in their history.

Stars are categorized by spectral class, with brown dwarfs being designated as types M, L, T, and Y.<ref name="ab" /><ref name="MichaelCushing2014">{{#invoke:citation/CS1|citation |CitationClass=citation }}</ref> Despite their name, brown dwarfs are of different colors.<ref name="ab" /> Many brown dwarfs would likely appear magenta to the human eye,<ref name="ab" /><ref name=Burrows2001>{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> or possibly orange/red.<ref name="Cain">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Brown dwarfs are not very luminous at visible wavelengths.

Some planets are 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. DENIS-P J082303.1-491201 b is listed as the most-massive known exoplanet (as of March 2014) in NASA's exoplanet archive, despite having a mass ({{safesubst:#invoke:val|main}} MJ) more than twice the 13-Jupiter-mass cutoff between planets and brown dwarfs.<ref>[1]</ref>


Brown dwarf sections
Intro  History  Theory  Observations  Planets around brown dwarfs  Superlative brown dwarfs  See also  References  External links  

PREVIOUS: IntroNEXT: History
<<>>