Well, nearby is relative, this object is nine light-years away, that’s over 50 trillion miles for us earthlings! But cool is correct no matter what part of the universe you live in. This brown dwarf is a balmy 25 C, about 80 F.
“The brown dwarfs we were turning up before this discovery were more like the temperature of your oven,” said Davy Kirkpatrick, a WISE science team member at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, Calif. “With the discovery of Y dwarfs, we’ve moved out of the kitchen and into the cooler parts of the house.”
Brown dwarfs are objects that didn’t make it to starhood, they lack enough mass to sustain hydrogen fusion in their center (The closest thing to a brown dwarf in our solar system is Jupiter). Astronomers classify brown dwarfs by letter, starting with class L for the hottest and Y for the coolest. Dim and distant, they’re very hard to see. They could be more common than stars, meaning our corner of the Milky Way galaxy could be swimming in them for all we know and our nearest interstellar neighbor could be a brown dwarf instead of the Centauri system 4.3 light-years away..
This is a gas ball, at some point under those dense clouds the temperature exceeds 25 C by a comfortable margin (It’s probably hot enough to melt iron within just a few hundred miles below the cloud tops). It’s a good bet some of these objects have moons — or would they be classified as planets? Either way, those smaller objects could experience tidal flexing like the Galileon moons of Jupiter. Io, the inner most moon of Jupiter, is the most volcanic body known in the solar system, Europa and Ganymede are both covered with fresh ice suggesting a surface that is regularly sculpted anew by cyro-geology, possibly driven by geothermal vents far below in a vast underground ocean.
That could be a very alien environment, but its possible specialized bacteria or their ET equivalents could cluster around the hypothetical heat sources, it’s even possible more sophisticated communities could develop around those simple organisms similar to the enigmatic ecosystems around earth’s black smokers and cold seeps. But protected by thick ice, circling a cool brown dwarf light years away, it will be a long, long time before we ever find that out, if we ever do. Europa on the other hand …