The same team that recently discovered the possibly water-covered, life-supporting planet, Kepler 22b, two weeks ago announced the discovery of two more Earth-sized planets on Monday. Ars Technica's John Timmer notes the Kepler system is now believed to contain five planets, and one of the two new planets, Kepler 20e, is the "smallest exoplanet yet detected." While the discovery of similarly sized planets isn't the blockbuster shock that Kepler 22b was two weeks ago, the astronomers more evidence that our solar system is not unique in hosting a large variety of different planets, including the elusive Earth-twin. (Keppler 22b is within what scientists call "habitable zone" where "liquid water could exist on a planet’s surface," but it is over twice the size of Earth and so not considered an Earth-twin.) On a conference call for reporters, one scientist on the Kepler team explained that the tools for detecting these planets are getting better rapidly, and we could know if an Earth-twin exists "in the next year or two." Merry Christmas, space nerds.
Update (7:45 p.m.): Space.com posted some artists' renderings of the two new planets, Kepler 22e and 20f, on Tuesday afternoon. Neither looks very friendly life-frindly
Kepler 22e is a rocky planet without an atmosphere, Science.com explains:
Kepler-20e is the first planet smaller than the Earth discovered to orbit a star other than the sun. A year on Kepler-20e only lasts 6 days, as it is much closer to its host star than the Earth is to the sun. The temperature at the surface of the planet, around 1400 degrees Fahrenheit, is much to hot to support life, as we know it.
Kepler 20f looks a little bit friendlier to life, but it's still too hot. From Space.com again:
Kepler-20f is the closest object to the Earth in terms of size ever discovered. With an orbital period of 20 days and a surface temperature of 800 degrees Fahrenheit, it is too hot to host life, as we know it.