We’ve talked about brown dwarfs here on Universe Today for years and years.  These are the “failed stars”; objects with too little mass to fully ignite nuclear fusion in their cores. Instead of blazing with red, yellow or the white light of our own stars, they’re heated by the gravitational collapse of material. They’re called brown dwarfs, but you might be surprised to know that they aren’t actually brown. In fact, it’s impossible to have brown light. So  what color are they?

The term “brown dwarf” was originally coined by Jill Tarter in 1975 to describe these objects, and there were other suggestions for names, like planetar and  substar. But the name “brown dwarf” stuck. And here’s the problem, as described by Jill Tarter, “it was obvious that we needed a color to describe these dwarfs that was between red and black. I proposed brown and Joe (Silk) objected that brown was not a color.”

http://wise.ssl.berkeley.edu/gallery_browndwarflineup.html

A Trio of Brown Dwarfs

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This artist's conception illustrates what brown dwarfs of different types
might look like to a hypothetical interstellar traveler who has flown a
spaceship to each one. Brown dwarfs are like stars, but they aren't massive
enough to fuse atoms steadily and shine with starlight -- as our sun does so
well.

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Brown Dwarfs are Hybrids of Large Planets and Small Stars

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[Photo Link]