The astronomers -- Trent Dupuy and Michael Liu of the University of Hawaii and Michael Ireland of the University of Sydney -- used both the orbiting Hubble Space Telescope, and the Keck II Telescope in Hawaii.

."These are very challenging measurements, because brown dwarf binaries have tiny separations on the sky and orbit each other very slowly. We needed to obtain the sharpest measurements that are possible with current telescopes to precisely monitor their motion," said Trent Dupuy of the University of Hawaii.

The two brown dwarf binaries examined were 45 to 60 light years from Earth, with brown dwarfs in one of the systems each having just 3 percent of the sun's mass; the two in the other system each had a mass less than 6 percent of that of the sun.

The team is to report its study in a future issue of the Astrophysical Journal.