NASA's Kepler Confirms Its First Planet In Habitable Zone

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Whitney Clavin 818-354-4673
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Michele Johnson 650-604-6982
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Trent J. Perrotto 202-358-0321
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News release: 2011-373 Dec. 5, 2011

NASA's Kepler Confirms Its First Planet In Habitable Zone

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-373&cid=release_2011-373

PASADENA, Calif. -- NASA's Kepler mission has confirmed its first planet in the "habitable
zone," the region around a star where liquid water could exist on a planet's surface. 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. Candidates require follow-up observations to verify they are actual planets.

The newly confirmed planet, Kepler-22b, is the smallest yet found to orbit in the middle of the
habitable zone of a star similar to our sun. The planet is about 2.4 times the radius of Earth.
Scientists don't yet know if Kepler-22b has a predominantly rocky, gaseous or liquid
composition, but its discovery is a step closer to finding Earth-like planets.

Previous research hinted at the existence of near-Earth-size planets in habitable zones, but clear
confirmation proved elusive. Two other small planets orbiting stars smaller and cooler than our
sun recently were confirmed on the very edges of the habitable zone, with orbits more closely
resembling those of Venus and Mars.

"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."

Kepler discovers planets and planet candidates by measuring dips in the brightness of more than
150,000 stars to search for planets that cross in front, or "transit," the stars. Kepler requires at
least three transits to verify a signal as a planet.

"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 Kepler science team uses ground-based telescopes and NASA's Spitzer Space Telescope to
review observations on planet candidates the spacecraft finds. The star field that Kepler observes
in the constellations Cygnus and Lyra can only be seen from ground-based observatories in
spring through early fall. The data from these other observations help determine which
candidates can be validated as planets.

Kepler-22b is located 600 light-years away. While the planet is larger than Earth, its orbit of 290
days around a sun-like star resembles that of our world. The planet's host star belongs to the
same class as our sun, called G-type, although it is slightly smaller and cooler.

Of the 54 habitable zone planet candidates reported in February 2011, Kepler-22b is the first to
be confirmed. This milestone will be published in The Astrophysical Journal.

The Kepler team is hosting its inaugural science conference at Ames Dec. 5-9, announcing 1,094
new planet candidate discoveries. 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 findings, based on observations conducted May 2009 to September 2010, show a dramatic
increase in the numbers of smaller-size planet candidates.

Kepler observed many large planets in small orbits early in its mission, which were reflected in
the February data release. Having had more time to observe three transits of planets with longer
orbital periods, the new data suggest that planets one to four times the size of Earth may be
abundant in the galaxy.

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. While this is a decrease from the 54
reported in February, 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.

"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 San Jose, Calif. "The more data we collect, the keener our eye for finding the
smallest planets out at longer orbital periods."

NASA's Ames Research Center manages Kepler's ground system development, mission
operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif.,
managed Kepler mission development.

Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system
and supports mission operations with the Laboratory for Atmospheric and Space Physics at the
University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler
science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science
Mission Directorate at the agency's headquarters.

For more information about the Kepler mission and to view the digital press kit, visit
http://www.nasa.gov/kepler .

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