Brown Dwarfs are sometimes referred to by scientists as "failed stars" because even though they contain many of the same elements as stars, they lack the mass needed to start the nuclear fusion process that goes on inside a star.



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They start out just like normal stars do, as a cloud of dust and gas collapsing and being pulled together by gravity. The difference with the Brown Dwarf is that they don't have the mass to create a gravity with temperatures hot enough to to start hydrogen fusion.

Brown Dwarfs were originally called Black Dwarfs but that is now a term used to refer to a start in its final stage of stellar evolution in which all of its heat has been radiated away.

Since Brown dwarfs are so cool in temperature in comparison to stars they can sometimes be mistaken for planets. Scientists officially determine if a Brown Dwarf is actually a Brown Dwarf and not a planet by whether or not is can fuse deuterium which is an isotope of hydrogen that contains one proton and one neutron in its nucleus.

Also, since they give off such little light they were not able to be found until recently as technology has gotten more advanced. Before the 1980's when the first Brown dwarf was seen, astronomers could only speculate on their existence.