First Earth-like extrasolar planet

The fictional setting for the movie Avatar is the forested planet of Pandora in the Alpha Centauri system around 4.4 light years away from our Solar System. Of the more than 700 planets orbiting other stars discovered to date, the first potentially Earth-like example is Kepler-22b. Its discovery was announced on 5 December 2011 and has caused excitement among astronomers due to its properties. The planet is about 2.4 times the size of Earth and it orbits its Sun-like star in around 290 days. The luminosity of its parent star, coupled with the orbital distance, means Kepler-22b is believed to reside within its star's habitable zone. If the planet has an Earth-like greenhouse effect then its surface temperature could be a comfortable 22 C. Kepler-22b is around 600 light years away.