Earth-Sized Alien Worlds Orbit One in Six Stars
Four years ago, NASA launched the Kepler space telescope in an attempt to learn just how common Earth-sized worlds are in the Milky Way galaxy. Now, scientists have unveiled part of the answer: About 17 percent – one in six – of Kepler’s target stars have Earth-sized worlds orbiting closer to their parent stars than where Mercury orbits the sun.
With about 100 billions stars in the Milky Way galaxy, that means there’s approximately 17 billion Earth-sized worlds, conclude astronomers who presented the research at the American Astronomical Society conference in California. More work is needed to determine how many extrasolar ‘Earths’ orbit farther away from their parent stars in so-called “habitable zones” where temperatures are suitable for water to exist in a liquid state on the planet’s surface. Water is necessary for life as we know it.