From Technology Review:
When sufficiently large clouds of dust and gas collapse under their own gravity, the temperatures and pressures generated at their hearts are large enough to trigger nuclear fusion. When that happens, a star is born.However, the original cloud must have a mass greater than a specific threshold for this to happen. When the cloud is too small, the conditions inside never trigger fusion and the star never switches on. These failed stars are called brown dwarfs and they are not as unfamiliar as they might sound.
Brown dwarfs have much in common with the planet Jupiter, which is thought to have about the same size, mass, and composition as these objects. If Jupiter had formed alone in the depths of space, it too would be classified as a failed star.
Brown dwarfs were first discovered in 1995, and since then astronomers have found several hundred others orbiting other stars, orbiting each other or simply wandering alone. No one knows how many there ought to be but the best guestimate is that there may be about a third as many brown dwarfs as there are stars, meaning that most remain undiscovered.
So the news from Philip Lucas at the University of Hertfordshire and a few pals that they have discovered one of these objects nearby is not entirely unexpected. They call this object, somewhat unromantically, UGPSJ0722-05.
[Read more at Technology Review]