Brown dwarfs are substellar objects that occupy the mass range between the heaviest gas giant planets and the lightest stars, of approximately 13 to 75–80 Jupiter masses, or approximately 2.5×10^28 kg to about 1.5×10^29 kg. A brown dwarf is a sub-stellar object that refers to objects that are formed the same way as true stars are, but aren't massive enough to undergo hydrogen fusion. They occupy the mass range in between large gas giants and low-mass stars, which is in between 13 and 80 times the mass of Jupiter. Brown dwarfs can be classified as either Class L, T, or Y. The light spectrum of a brown dwarf peak in the infrared. 

Brown dwarfs undergo deuterium fusion when they are over 13 times the mass of Jupiter, which is generally the case with T-dwarfs. If they're over 65 Jovian masses, which is often the case for L-dwarfs, they can go under lithium fusion, though L-types can fuse hydrogen and can be considered true stars when they are over 80 times the mass of Jupiter. If a brown dwarf is less than 13 Jovian masses, it is considered a sub-brown dwarf or a (rogue) planet, which is normally the case with Y dwarfs.

Despite their name, brown dwarfs aren't actually brown. L-types glow a deep reddish-orange in color, due to them emitting mostly red and infrared light. T-type dwarfs are a dark magenta or purple in color. This is because T-types don't burn heavy elements such as potassium or sodium, and leave as ions in their atmospheres. These ions absorb more red than blue, making the colors tend towards magenta.  Y-type brown dwarfs produce next to no light due to them not fusing anything, making them black, virtually invisible when there is no light source near them.

Brown Dwarf Classes
Y · T · L
Community content is available under CC-BY-SA unless otherwise noted.