How cool is this? Literally, the coolest: NASA’s Wide-field Infrared Survey Explorer has found the lowest-temperature brown dwarfs ever seen, the tail end of the stellar class of brown dwarfs called Y dwarfs. How not hot are they? This one (called WISE 1828+2650 if you’re playing brown dwarf bingo), spotted by WISE, has a surface temperature of 25° Celsius — that’s 80° Fahrenheit!
As I sit here and write this, it’s warmer outside my window than it is on the surface of that object!
Not only that, another Y dwarf they found, called WISE 1541-2250, may be the seventh-closest object in the sky outside our solar system.
The distance found is not directly measured; it was calculated using the brightness of the brown dwarf. The distance was found using parallax. Even though it’s only about nine light years away, it’s incredibly faint. The only reason it was seen at all is that WISE is tuned to see in the far-infrared, where these things are far brighter than in visible light.
The most exciting part about this is it supports an idea I’ve had (and lots of others have had too) for a long time: Proxima Centauri may not be the closest object to the Sun. A Y-class brown dwarf could be even closer and still have evaded our detection. Even at four light years away — roughly how far Proxima Cen is — a Y star would be pretty hard to see. We may not know for a while yet, but it’s possible.
So what’s the deal with brown dwarfs? Read More