Astronomy The great mystery of the first brown dwarf found is solved
The first "failed star" was discovered in 1995, but it was far too dim. The explanation is now astonishingly simple – and raises new questions.
Artistic representation of the two celestial bodies
(Image: Caltech)
Almost 30 years after the discovery of the first "failed star", or brown dwarf Gliese 229 B, two research groups have now independently solved its greatest mystery. Both have come to the conclusion that it is actually two brown dwarfs orbiting each other closely. So far, it has not been possible to explain why the object is significantly fainter than would be expected given its total mass. Astrophysicist Rebecca Oppenheimer, who was involved in the original discovery and in one of the new studies, now speaks of the "most exciting and fascinating discovery in substellar astrophysics in decades". But while this has answered a major question about the system, the team writes that it is now necessary to determine how the two objects were formed in the first place.
One answer, new questions
Brown dwarfs are celestial bodies that are not massive enough to ignite nuclear fusion as in stars, but at the same time are significantly more massive than (exo-)planets. Since the discovery of Gliese 229 B in 1995, numerous others have been found, including by amateur researchers. However, while the brightness of these objects usually matches the masses determined, Gliese 229 B was always considered too dark. With 70 times the mass of Jupiter, the celestial body should actually shine brighter, according to researchers. It is only now clear that this was based on a crucial misconception: instead of just one celestial body, there are two with 38 and 34 times the mass of Jupiter respectively. Both orbit each other and take 12 days to complete one orbit. It takes them 250 years to orbit their small red star. They are now officially called Gliese 229 Ba and Gliese 229 Bb.
How the two celestial bodies were formed is now the next big question. Although there are theories about this, it is not yet clear whether the processes are similar to those involved in the formation of planets and therefore whether double systems of exoplanets can also form. At the same time, however, the discovery already suggests that other such objects are waiting to be discovered, the team writes. In any case, the discovery deepens our knowledge of brown dwarfs. The discovery is presented in the journal Nature, among others, and another research article with the same result can be found in the Astrophysical Journal Letters.
(mho)