What percentage of Sun-like stars have earth-like planets orbiting them? As many as one-fourth, according to a new survey performed by astronomers at the University of California. This result contradicts previous theories of planet formation, but is a tantalizing prediction that finding extraterrestrial life, or at least Earth’s twin, is not impossible.

The researchers who published this finding are using the Keck HIRES instrument to monitor a sample of nearby stars to detect planets having masses of three to 1000 times the mass of Earth as part of the NASA-Eta-Earth survey. The gravitational tug of a planet shifts its host star in a small periodic motion as it orbits