NASA's Kepler mission has discovered 'a new Earth' for the first time in the history of science of the world. The newly discovered 'Kepler-22b' is the first confirmed planet in the "habitable zone," the area around a star where a planet could exist with liquid water on its surface.
The planet's radius is about 2.4 times that of the Earth. It is located about 600 light years away. Its orbital period is shorter than that of the Earth: a "year" on Kepler-22b is 290 days instead of 365.
There were two other planets confirmed this year by other projects in the habitable zone, but their stars are much cooler than our Sun, and their orbits are more like that of Venus or Mars, scientists say.
Kepler-22b is 15% closer to its star and we are to the Sun. But since Kepler-22b's star is dimmer, lower in temperature and smaller than our Sun, researchers' modeling suggests it is a similar temperature to the Earth, said Bill Borucki, Kepler principal investigator at NASA's Ames Research Center.
"If the greenhouse warming were similar on this planet and had a surface, its surface temperature would be something like 72 Fahrenheit, a very pleasant temperature here on Earth."
The warmer a planet, the more evaporation of water there would be, Borucki said. A planet can't have a surface temperature that's very hot without losing all of the surface water.
The Kepler mission reported in February that it had found 54 planet candidates in the habitable zone; Kepler-22b is the first of these to be confirmed, and those results will be published in The Astrophysical Journal. There are still 48 potential planets from that batch.