Nemesis. No, I don't mean the tenth Star Trek film, a film that many of us Trekkers would like to simply imagine never happened (and thanks to J. J. Abrams' rebooting of the franchise, we now can). Instead, I mean the long-theorized stellar companion to our Sun -- perhaps a brown dwarf star -- the existence of which could perhaps help to explain cycles of mass extinction on Earth. NASA's WISE satellite, presently conducting a survey of the...