Kepler-22b, our first planet in the habitable zone of a Sun-like Star
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This image is an artist's conception of planet Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. It is the first planet that NASA's Kepler mission has confirmed to orbit in a star's habitable zone -- the region around a star where liquid water, a requirement for life on Earth, could persist. The planet is 2.4 times the size of Earth, making it the smallest yet found to orbit in the middle of the habitable zone of a star like our sun.
Scientists do not yet know if the planet has a predominantly rocky, gaseous, or liquid composition. It's possible that the world would have clouds in its atmosphere, as depicted here in the artist's interpretation.
Kepler also has discovered more than 1,000 new planet candidates, nearly doubling its previously known count. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Since the last catalog was released in February, the number of planet candidates identified by Kepler has increased by 89 percent and now totals 2,326. Of these, 207 are approximately Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter. The number of Earth-size and super Earth-size candidates has increased by more than 200 and 140 percent since February, respectively. There are 48 planet candidates in their star's habitable zone, a decrease from the 54 reported in February, because the Kepler team has applied a stricter definition of what constitutes a habitable zone in the new catalog, to account for the warming effect of atmospheres, which would move the zone away from the star, out to longer orbital periods.
Quotes from Kepler team:
"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. "Kepler's results continue to demonstrate the importance of NASA's science missions, which aim to answer some of the biggest questions about our place in the universe."
"Fortune smiled upon us with the detection of this planet," said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, Calif., who led the team that discovered Kepler-22b. "The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season."
"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 potentially habitable," said Natalie Batalha, Kepler deputy science team lead at San Jose State University in California. "The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods."
This diagram below compares our own solar system to Kepler-22. The diagram includes the habitable zone where water can exist in liquid form. Kepler-22's star is a bit smaller than our sun, so it's habitable zone is slightly closer in. The orbit of Kepler-22b around its star takes 289 days and is about 85% as large as Earth's orbit.
Both images credit: NASA/Ames/JPL-Caltech
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