http://www.nasa.gov/keplerbriefing0723 As I type this, NASA is announcing discovery of a new planet Kepler 452b that is - small and (probably) rocky like Earth - orbits a G2 star - is in the star's habitable zone This is the first candidate that meets all three criteria. (Most Earth-twins so far discovered are around tiny red dwarfs, and orbit in a matter of days) It has a 385 day long year, almost exactly the same as Earth. Kepler 452b is a slightly older sibling of Earth - it has lived in its habitable zone for 6 billion years. It's a little bigger, surface gravity is about 2x Earth, but it probably has a thick atmosphere as well as volcanism. One implication of this discovery is that these are surely common. We only detect 1 in 50 planets because of alignment issues, so detection of one suggests another 50 out there we can't see with current equipment. The one imperfection in this otherwise ideal Earth-sister is that it is more than 1300 light years away.