In fact, the chemical composition of GL229B's atmosphere looks remarkably like that of Jupiter. The discovery is an important first step in the search for planetary systems beyond the Solar System because it will help astronomers distinguish between massive Jupiter-like planets and brown dwarfs orbiting other stars. Caltech astronomers Kulkarni, Tadashi Nakajima, Keith Matthews, and Ben Oppenheimer, and Johns Hopkins scientists Sam Durrance and David Golimowski first discovered the object in October 1994. Follow-up observations a year later were needed to confirm it is actually a companion to Gliese 229. The astronomers suspect that the brown dwarf developed during the normal star-formation process as one of two members of a binary system.
Astronomers say the difference between planets and brown dwarfs is based on how they formed.
Planets in the Solar System are believed to have formed out of a primeval disk of dust around the newborn Sun because all the planets' orbits are nearly circular and lie almost in the same plane. Brown dwarfs, like full-fledged stars, would have fragmented and gravitationally collapsed out of a large cloud of hydrogen but were not massive enough to sustain fusion reactions at their cores. The orbit of GL229B could eventually provide clues to its origin. If the orbit is nearly circular then it may have formed out of a dust disk, where viscous forces in the dense disk would keep objects at about the same distance from their parent star. If the dwarf formed as a binary companion, its orbit probably would be far more elliptical, as seen on most binary stars.