For decades, the ten stars closest to our own Sun made a pretty static list. Ideas about where to send the first interstellar probes tended to focus on the same three or four star systems which all lie well within ten light years.

But in the last few years,

NASAs WISE spacecraft, in particular, has caused celestial cartographers to redraw their star maps to include recently discovered cooler and lower mass stars and even brown dwarfs. Brown dwarfs are conventionally defined as stellar-type objects from between 13 to 74 Jupiter masses that are simply too small to ignite thermonuclear burning of hydrogen in their cores. However, some brown dwarfs are thought to burn deuterium.

Artists conception of the binary system WISE J104915.57-531906 with the Sun in the background. Credit: Janella Williams, Penn State University.

The new third and fourth nearest stellar objects are now known to actually be cool brown dwarfs found last year with WISE (Wide-field Infrared Survey Explorer) mission data.

Id like to visit Wise1049-5319 and Wise0855-0714 most because I discovered them, said Kevin Luhman, an astronomer at Penn State University. Wise1049-5319 is a binary system in which the companions have masses of roughly 50 times the mass of Jupiter, he says, and as far as we know, Wise0855-0714 is a single object with a probable mass between 3 and 10 times the mass of Jupiter.

Its surface temperature is similar to the North Pole, making it the coldest object seen outside the solar system, probably with clouds of water ice in its atmosphere, said Luhman. If a probe visited either system, one would want it to come within one [Earth-Sun] distance or less to study these brown dwarfs in detail.

But undoubtedly the first stop would be nearby Proxima Centauri at only 4.2 light years away in the Alpha Centauri star system. As an M-spectral type red dwarf, it remains closest known star to earth, but is widely-separated from Alpha Centauri A & B the next nearest stars to Earth.

At only 6 light years away, Barnards star in the constellation of Ophiuchus is the second closest stellar system to Earth. And although this high-velocity red dwarf star has a long history of astronomers who have claimed that it harbors planets. No such detections have thus far been corroborated, however.

The nearest stars are still the G, M, and K spectral types, says Davy Kirkpatrick, an infrared astronomer at Caltech. But when you start getting to twenty down the list in terms of distance, he says, you start picking up L and T brown dwarfs, about the radius of Jupiter, that werent known to exist 15 years ago.

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NASA's WISE Mission Shuffles Sun's Nearest Stellar Neighbors