Kepler-22b

Kepler-22b is the first confirmed extra solar planet which could be a Super-Earth orbiting in the habitable zone of a Sun-like star discovered by NASA's Kepler Space Telescope.

Discovery

The discovery was announced December 5, 2011. The planet was originally discovered on Kepler's third day of science operations in mid-2009. The third transit was detected in late 2010. Additional confirmation data was provided by the Spitzer Space Telescope and ground-based observations. The planet's radius is roughly 2.4 times the radius of Earth; it is 600 light years away from Earth, in orbit around the G-type star Kepler 22.

Composition and structure

To date, its mass and surface composition remain unknown. If it has an Earth-like density (5.515 g/cm3) then it would contain 13.8 Earth masses, while its surface gravity would be 2.4 times Earth's. If it has water-like density (1 g/cm3) then it would mass 2.5 Earths and have a surface gravity of 0.43 times Earth's. The planet may fall into the category of planets known as super-Earths, depending on what the actual mass is.

Possibility of life

The distance from Kepler-22b to its host star is about 15% less than the distance from Earth to the Sun, but the luminosity (light output) of Kepler-22b's star is about 25% less than that of the Sun. This combination of a shorter distance from the star and a lower stellar luminosity are consistent with a moderate surface temperature. Scientists estimate that in the absence of an atmosphere, the equilibrium temperature would be approximately -11°C. If the atmosphere provides a greenhouse effect similar in magnitude to the one on Earth, the planet would have an average surface temperature of 22 °C (72°F).

At 2.4 times the size of the Earth, Kepler 22b is substantially larger than Earth and may therefore have a different composition. For example, the newly discovered planet may not be Earth-like, but rather more like Neptune, which is mostly ocean with a small rocky core. Nonetheless, Natalie Batalha, one of the scientists on the project, speculated "it's not beyond the realm of possibility that life could exist in such an ocean."

Source: http://www.wikipedia.org/