Outer space is chock-full of stars and planets orbiting them, but there’s a fine line between what makes a star a star and a planet a planet. That aside, there’s one type of objects that blurs the line somewhat – an object known to astronomers as a brown dwarf.
As we know, stars are effectively giant reacting orbs of nuclear fusion existing in outer space, and they vary in size; it’s their immense mass that makes nuclear fusion possible in the first place. Planets, on the other hand, are much less massive, and typically either gassy or terrestrial by nature. Thanks to being far less massive than stars, even larger gassy planets like Jupiter aren’t capable of sustaining nuclear fusion like a star can. But could it?
Theoretically, if we dumped a substantial (and frankly unrealistic) amount of mass into Jupiter, then the forces at work could allegedly jump start nuclear fusion. But even then, would that be enough to transform it into a star? It would depend on just how much mass got dumped into Jupiter – adding just enough could hypothetically give it the oomph it needs to become a star, but stopping just short of that would result in the aforementioned brown dwarf.
For the longest time, brown dwarfs were merely theoretical, but in 1995, astronomers discovered their first specimen and validated that it was indeed a brown dwarf after performing a lithium measurement. After that, more and more brown dwarfs were discovered, helping astronomers to realize that were was indeed a such thing as a sub-stellar object, or a ‘failed star.’
With the introduction of NASA’s Wide-Field Infrared Survey Explorer (WISE), astronomers were able to make more detailed observations of the cosmos in the infrared light spectrum. With that, hundreds more brown dwarfs were discovered, with many ranging in temperature. These varying temperatures resulted in different classifications, categorized via letters of the alphabet to help astronomers distinguish between the hottest and the coolest.
Astronomers still have much to learn about brown dwarfs, and the coolest ones are so difficult to spot that we still don’t even know what color it may actually look like in outer space with the naked eye. As future space observatories launch, perhaps we’ll get the opportunity to better understand brown dwarfs and their reason for existence in nature.