Kelu-1 – a Binary or Triple System of Brown Dwarfs

Several hundred Brown Dwarfs have been identified in the solar neighborhood and seem to be as numerous as main sequence stars. But the models for their structure and evolution are not as reliable as the models for stars. Spatially resolved binary systems offer a unique opportunity to determine the masses without using models, but such cases are rare. A group at the MPIA has now succeeded in determining the parameters of the Brown Dwarfs Kelu-1A and B. Conclusion: Existing models yield masses which are too low. The spectra also suggest the presence of an invisible third Brown Dwarf in Kelu-1.