The more astronomers look for other worlds, the more they find that it is a crowded and crazy cosmos. They think planets easily outnumber stars in our galaxy and they are even finding them in the strangest of places. And they have only begun to count. Three studies released Wednesday, in the journal Nature and at the American Astronomical Society's conference in Austin, Texas, demonstrate an extrasolar real estate boom. One study shows that in our Milky Way, most stars have planets. And since there are a lot of stars in our galaxy — about 100 billion — that means a lot of planets. “We're finding an exciting potpourri of things we didn't even think could exist,” said Harvard University astronomer Lisa Kaltenegger, including planets that mirror “Star Wars” Luke Skywalker's home planet with twin suns and a mini-star system with a dwarf sun and shrunken planets. “We're awash in planets where 17 years ago we weren't even sure there were planets” outside our solar system, said Kaltenegger, who wasn't involved in the new research. Astronomers are finding other worlds using three different techniques and peering through telescopes in space and on the ground. Confirmed planets outside our solar system — called exoplanets — now number well over 700, still-to-be-confirmed ones are in the thousands. NASA's new Kepler planet-hunting telescope in space is discovering exoplanets that are in a zone friendly to life and detecting planets as small as Earth or even tinier. That is moving the field of looking for some kind of life outside Earth from science fiction toward plain science. One study in Nature this week figures that the Milky Way averages at least 1.6 large planets per star. And that is likely a dramatic underestimate. That study is based on only one intricate and time-consuming method of planet hunting that uses several South American, African and Australian telescopes. Astronomers look for increases in brightness of distant stars that indicate planets between Earth and that pulsating star. That technique usually finds only bigger planets and is good at finding those further away from their stars, sort of like our Saturn or Uranus. Kepler and a different ground-based telescope technique are finding planets closer to their stars. Putting those methods together, the number of worlds in our galaxy is probably much closer to two or more planets per star, said the Nature study author Arnaud Cassan of the Astrophysical Institute in Paris.
