Nearby orbiting pair of failed stars may be harboring a planet

An orbiting duo of failed stars, the closest such pair to our sun, may by harboring a third, planetary-mass object, U.S. and European astronomers report. That's the evidence of precise measurements of the closest pair of brown dwarfs -- bodies with a mass below 8 percent of the mass of the Sun, so not massive enough to burn hydrogen in their centers -- made by Carnegie Institution astronomer Yuri Beletski and colleagues, the institution said Monday. The binary system, Luhman 16AB, was discovered earlier this year and is only 6.6 light-years away from Earth. Both objects have a mass between 30 and 50 Jupiter masses, the astronomers said. "The two brown dwarfs are separated by about three times the distance between the Earth and the Sun," Beletsky said. "Binary brown dwarf systems are gravitationally bound and orbit about each other. Because these two dwarfs have so little mass, they take about 20 years to complete one orbit." Precise measurements of the positions of the two brown dwarfs revealed very small deviations from the expected motion of the pair around each other, the researchers said, a strong indication that a companion perturbs the motion of one of the two brown dwarfs. This companion is most likely a planetary-mass object with an orbital period between two months and a year, they said. "Further observations are required to confirm the existence of a planet," research team member Henri Boffin of the European Southern Observatory said. "But it may well turn out that the closest brown dwarf binary system to the Sun turns out to be a triple system!"