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Meet the brown dwarf: bigger than a planet, and smaller than a star. A category of its own, it\u2019s one of the strangest objects in the universe.<\/p>\n
<\/p>\n Brown dwarfs typically are defined to have masses anywhere from 12 times the mass of Jupiter right up to the lower limit for a star. And despite their names, they are not actually brown. The largest and youngest ones are quite hot, giving off a steady glow of radiation. In fact, the largest brown dwarfs are almost indistinguishable from red dwarfs, the smallest of the stars. But the smallest, oldest, and coldest ones are so dim they can only be detected with our most sensitive infrared telescopes.<\/p>\n Unlike stars, brown dwarfs don\u2019t generate their own energy through nuclear fusion, at least not for very long. Instead they emit radiation from the leftover heat of their own formation. As that heat escapes, the brown dwarf continues to dim, sliding from fiery red to mottled magenta to invisible infrared. The greater the mass at its birth, the more heat it can trap and the longer it can mimic a proper star, but the ultimate end fate is the same for every single brown dwarf, regardless of its pedigree.<\/p>\n At first it may seem like brown dwarfs are just extra-large planets, but they get to do something that planets don\u2019t. While brown dwarfs can\u2019t fuse hydrogen in their cores \u2013 that takes something like 80 Jupiter masses to accomplish \u2013 they can briefly partake in another kind of fusion reaction.<\/p>\n \n