Asked by Dave Richardson
Although brown dwarfs have some similarities to both planets and stars they don’t quite fit either category. They’re believed to form through the same process as other stars, made when gas and dust coalesce, but without the mass to sustain prolonged hydrogen fusion at the core.
After formation, these objects are too small to be considered a star (we refer to them in terms of Jupiter masses, not solar masses) and have a surface temperature less than 2,500 degrees Celsius (4,532 degrees Fahrenheit). They fit somewhere between our current definitions of stars and planets suggesting that perhaps these two classes are not as clear cut as we first thought.
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