Astronomer Locates Previously Unseen Neighbor to the Sun

When NASA launched the WISE satellite in 2009, astronomers hoped it would be able to spot loads of cool, dim objects known as brown dwarfs. Bigger than a planet, a brown dwarf is not quite a star, either—it is too small to sustain the nuclear fusion reactions that turn hydrogen to helium. But it may burn to some degree, using a heavy isotope of hydrogen called deuterium as fusion fuel.

Because brown dwarfs are so dim, it is entirely possible that some of them lie very close to the sun—as close as any known star—and have yet to be discovered. But more than three years after WISE (short for the Wide-Field Infrared Survey Explorer) launched, the map of the sun’s immediate vicinity has remained largely unchanged. Until now.

In a study to appear in the Astrophysical Journal Letters (pdf), Kevin Luhman, an associate professor of astronomy and astrophysics at Pennsylvania State University, announced that he has located a previously unknown denizen of the sun’s neighborhood. Using data from WISE, Luhman has identified a pair of brown dwarfs, bound into a binary system, just 6.5 light-years away. That is nearer to the sun than all but two known star systems, both of which were located more than 95 years ago: the Alpha Centauri triple star system (about 4.3 light-years away) and Barnard’s Star (six light-years).

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