An artist's impression of Kepler-22b, the first confirmed planet to be found by Kepler in the habitable zone around its parent starCredit: NASA/AMES/JPL-Caltech
NASA scientists have confirmed that the Kepler space telescope has identified a planet, Kepler-22b, that exists in the habitable or 'Goldilocks' zone around its parent star – that is, the region where surface temperatures are such that liquid water could exist.
So far Kepler has identified over 2,300 new planetary candidates, including 48that exist within their parent star's habitable zone, of whichten are of near-Earth size. Kepler-22b is the first candidate in a habitable zone to be confirmed as a planet, with the initial Kepler observations of its transit in 2010 now backed up by observations using the Spitzer Space Telescope and ground-based telescopes. The planet has a radius 2.4 times the size of Earth and is located about 600 lightyears away. It orbits its parent star – a G-type star similar to, but slightly smaller than, our own Sun – every 290 days.
It is not yet known whether Kepler-22b is of rocky, gaseous or liquid composition. Nevertheless, "This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, a Kepler program scientist at NASA's Washington Headquarters.
The latest published Kepler findings show a marked increase in the number of Earth-size candidates detected. There are now 207 Earth-size candidates, as well as 680 potential 'super-Earths'.
"The tremendous growth in the number of Earth-size candidates tells us that we're honing in on the planets Kepler was designed to detect:those that are not only Earth-size, but also are potentiallyhabitable," said Natalie Batalha, Kepler deputy science team lead atSan Jose State University in California.