spacetoday.net: Brown dwarfs heavier than expected

Posted: Thu, Jan 20, 2005, 7:43 AM ET (1243 GMT)
Brown dwarf AB Dor C (ESO/Univ. of Arizona)

Brown dwarfs, objects intermediate in size between stars and planets, may be twice as heavy as predicted, a finding that could raise doubts about the discovery of some extrasolar planets. Astronomers used the European Southern Observatory's Very Large Telescope to observe a brown dwarf orbiting a young, nearby star. From the orbit, astronomers determined that the brown dwarf has a mass 88-98 times that of Jupiter, but with a temperature and luminosity consistent with an object half as massive, according to current models. Astronomers concluded that brown dwarf models underestimate the mass of such objects by a factor of two. This means that some objects previously identified as "free-floating" exoplanets — objects with the mass of planets but not bound to any star — may in fact be much heavier and thus could be considered brown dwarfs instead.