= Brown dwarf
{wiki}
A <brown dwarf> is a self-gravitating body that does not sustain ordinary core <hydrogen burning>. Contraction initially heats it, but growing <electron degeneracy pressure> limits further compression before long-lived hydrogen fusion can establish the thermal balance of a <main-sequence star>. It subsequently cools and becomes fainter.
Some <brown dwarfs> temporarily burn <deuterium>; the <deuterium-burning mass> is a composition-dependent classification scale rather than a unique formation test. Their <radii> can be close to <Jupiter>'s across a broad <mass> range. Consequently, <exoplanet transit photometry> alone cannot distinguish a giant <planet> from a <brown dwarf>. The transit and <Doppler spectroscopy> measurements of <CoRoT-3b> illustrate why independent <mass> information is decisive for characterizing such compact companions.
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