It was a major feat last year when a team of astronomers announced it had detected two Earth-sized planets circling very close to a star called Kepler-20, which is 950 light-years away. Now, scientists say that such planets are not uncommon at all — one in every six stars has an Earth-sized world.

A team from the Harvard-Smithsonian Center for Astrophysics announced the new result last Monday at the meeting of the American Astronomical Society in Long Beach, Calif. The 17 billion Earth-sized worlds scientists say are lurking in the Milky Way are so close to their stars that they would be far too sweltering for life, at least as we know it.