A Shortcut for Planet Hunters

摘要

Learning your planets used to be a lot easier. There were only nine of them, and they all circled our own sun. With Pluto kicked out of the club for failing to make weight, the local census has dwindled even further. But the sun we know is hardly the only one around, and elsewhere in the cosmos, planets are popping up everywhere. Earlier this month, astronomers from San Francisco State University, the University of California, Berkeley, and the Carnegie Institution of Washington announced the discovery of a fifth planet around the star 55 Cancri, which is 41 light-years away in the constellation Cancer. The find makes that star system the most heavily populated one known other than our sun's and raises to 265 the total of extrasolar planets since astronomers began discovering them in 1995. To skywatchers, however, 55 Cancri is special, not just because of its litter of worlds but because of what it tells us about the possibility of life around it—and other stars.