ENCORE The stars are out tonight. And they do more than just twinkle. These boiling balls of hot plasma can tell us something about other celestial phenomena. They betray the hiding places of black holes, for one. But they can also fool us. Find out why one of the most intriguing discoveries in astrobiology - that of the potentially habitable exoplanet Gliese 581g - may have been just a mirage.
Plus, the highest levels of ultraviolet light ever mentioned on Earth’s surface puzzles scientists: is it a fluke of nature, or something manmade?