Astronomers recently discovered two brown dwarfs in our solar neighborhood, and they're actually pretty close by: 15 and 18 light years away!
[Click to hugely unendwarfenate.]
The two objects were spotted in observations made by WISE, the Wide-field Infrared Survey Explorer, which recently finished its mission to observe the entire sky in infrared light. In the false color images from WISE, brown dwarfs tend to appear very green (fun details are in that link), making them somewhat easy to spot against full-blown stars which tend to appear blue -- remember, this is false color!
Anyway, the astronomers were looking for nearby brown dwarfs (PDF), so they searched for green objects that had no obvious counterparts in older infrared surveys. All stars orbit the center of the Milky Way galaxy at different velocities, and over time that means they move across the sky. Nearby stars appear to move fastest (just like the nearby trees fly past you while driving, but distant mountains appear to move more slowly), so nearby brown dwarfs would have moved in the time separating the older surveys from that of WISE.
The astronomers actually found quite a few objects, most of which were known. But these two, called WISE J0254+0223 and WISE J1741+2553, were not previously known -- in the picture above, their positions in the older survey from 2000 are labeled compared to their positions in the 2010 WISE images. Remarkably, only 39 star systems (I include multiple stars as one system here) are known to be closer to us than J1741 (which is 15 light years away), and only a handful of them are brown dwarfs (what are called T class objects).
Which, as always when we find new nearby stars, make me wonder: are there faint, cool brown dwarfs even closer to us? Is it possible that Proxima Centauri, a red dwarf 4.2 light years away, is not the closest star to the Sun?
Maybe. The WISE data used to find these two neighbors is not the full set taken by the spacecraft. There's still quite a bit of data to sift through. Who knows, we may yet find out there's a star or stars passing by still waiting to make our acquaintance.
- WISE finds the coolest stars. Literally.
- The galaxy may swarm with billions of wandering planets
- Are we in danger from a rogue planet?
- The case of the brown star that's really red or possibly blue