spacetoday.net: Study: billions of Earth-sized planets in our galaxy

Study: billions of Earth-sized planets in our galaxy

Posted: Fri, Oct 29, 2010, 8:01 AM ET (1201 GMT)
Gliese 581g illustration (Lynette Cook)

A new study concludes that the Milky Way galaxy may be home to nearly 50 billion planets approximately the size of the Earth. The research, published in the current issue of the journal Science, determined that number by examining the statistics of extrasolar planets discovered to date within 80 light-years of the Earth and then extrapolating the trend in sizes to smaller worlds, like the Earth. That analysis found that 23 percent of Sun-like stars in the galaxy should have Earth-sized planets, far more than have much larger planets, meaning that for an approximate population of 200 billion such stars in the galaxy, there should be at least 46 billion Earth-sized planets.