NASA's Kepler spacecraft hunting for Earth-like planets around other stars

has found 706 candidates for potential alien worlds while gazing at more than 156,000 stars

Since transits of planets in the habitable zone of solar-like stars occur about once a year and require three transits for verification, it is expected to take at least three years to locate and verify an Earth-size planet. The expectation is that Kepler should be able to identify at least 60 habitable earthlike planets in its 500 light year range.