The Kepler Space Telescope, an observatory launched by NASA in 2009 to find Earth-like planets, has provided data that suggests there are billions of them -- enough that one in six stars may have at least one orbiting it.
Out of roughly 100 billion stars in the Milky Way galaxy, a new analysis of Kepler data shows that around 17 percent of them have Earth-sized planets orbiting them, meaning there could be as many as 17 billion Earth-sized worlds.
Source: ABC News. Read full article. (link)