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.
A brown dwarf is a type of celestial object that falls between the largest planets and the smallest stars in terms of mass. Specifically, brown dwarfs have masses ranging from about 13 times the mass of Jupiter (approximately 0.012 times the mass of the Sun) to around 80 times the mass of Jupiter (about 0.07 times the mass of the Sun). They are not massive enough to sustain hydrogen fusion in their cores, which is the defining characteristic of true stars.
New to topics? Read the docs here!