GOOD news for all those who fret about the fate of life in the cosmos. Dan Hooper and Jason Steffen of Fermilab in Batavia, Illinois, calculate that the dark matter that lies at the heart of the galaxy could heat an alien world enough to make it habitable, even without the warm glow of starlight (see 鈥淒ark matter could make planets habitable鈥�).
Astronomers are far from impressed, since these dark-matter worlds will be hard to detect. But surely that is not the point. These free-floating worlds 鈥� if they exist 鈥� would be the only warm spots left trillions of years from now (New 杏吧原创, 2 April, p 37). If nothing else, this work illustrates how we have yet to think through the possibilities for extending a star鈥檚 Goldilocks zone, where Earth-like planets are awash with liquid water. Even when all the starlight has faded, life may find a way.