Discovery: Neptune in the habitable zone of the Sun

With the Kepler space observatory, astronomers have discovered the smallest planet in the habitable zone navigating a Sun-like star. But Kepler 22-b is still 2.4 times larger than Earth. This is probably the size of a planet of Neptune.The area where water can flow to the surface
Kepler 22-b runs in 290 days around 22 Kepler, a sun-like star located 600 light years, which puts cell in the habitable zone, that is to say the area where the climate of a planet can allow water to flow on the surface.

Below is a comparison of the solar system and the system of Kepler 22 shows that, like Earth, Kepler 22b sailing in the habitable zone. (Credit: NASA / JPL-Caltech / Ames / Sky and Space Pictures).

Credit: NASA / JPL-Caltech / Ames / Sky and Space Pictures
With this discovery, researchers planets took a step towards the detection of their Holy Grail: a twin of Earth in the habitable zone of a sun. But they have not yet.

Or ocean planet Neptune?
Currently, the team has not observed the star through the swing of it causes the star (the so-called radial velocity). Consequently, researchers do not know its mass and therefore can not deduct its density.
But if its radius is 2.4 times that of Earth, there is very little chance for it to be rocky. The models indicate that if its mass is low (1 or 2 Earth masses), it is a gaseous planet. If it is more massive (5 to 10 Earth masses), we are dealing with an ocean planet, that is to say a planet that contains so much water that it is entirely covered by a sea of ​​tens of km in thickness.
Thousands of potential planets
Kepler 22-b is not much more like Earth than is Gliese 581d. 5.6 times more massive than our planet, which sails in the habitable zone of a red dwarf, a star cooler than our Sun.Hunting Kepler planets by the transit method. The NASA space observatory captures the small drop in brightness that causes the passage of a planet to its star. To date, the team announced that it has detected 2326 candidates. Among the planets, which have yet to be confirmed, there were 207 Lands, Land Super 680, 1181 Neptune, Jupiter and 55 203 planets more massive than Jupiter.
SETI listening to the planets Kepler
48 of them, including Kepler 22-b, browse the habitable zone of their star. They are the ones that the Allen telescope array (ATA, Allen Telescope Array) located in California and dedicated to the SETI search of extraterrestrial intelligence, will point priority (1).ATA had been in "hibernation" since April due to lack of funding. Public support and the Air Force has put it back in service on December 5.