Kepler has discovered a planet in the habitable zone of its sun-like star. It has a 290 day year, and a temperature of 22C, assuming a greenhouse effect similar to Earths (though with a thicker atmosphere, it is probably much hotter.) The planet has a radius 2.4 times that of the earth. This probably means that it has significant amounts of hydrogen in its atmosphere and has a deep ocean on its surface, covering all the land in miles of water. It's probably better to think of it as a warm Neptune than another Earth.
A few other facts:
- It is about 600 light years away in the direction of the constellation Cygnus.
- Its star is 25% cooler than our sun, but the planet orbits 15% more closely than Earth, so it works out temperature-wise.
- There are conflicting reports about the surface gravity. It is definitely higher than Earth, but the exoplanet catalog lists 4.84g, while Phil Plait estimates 2.4g, so I'm not sure what to believe.
- Kepler has found another 1000 planet candidates since the last update in February. They've been confirming the Kepler finds with Spitzer, and found that all the ones they've checked so far were real, so the error rate on Kepler detections is probably very low. Of these, I would estimate they've found more than a dozen new candidates that are at least as good as the five near-habitable ones they announced in February, but they haven't given any details about these yet. The conference is still ongoing, though, so there may be an announcement this week.
- Here is a nice summary image of the confirmed planets found so far by all methods: