Trent J. Perrotto
Headquarters, Washington
202-358-0321
trent.j.perrotto@nasa.gov

Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-6982
michele.johnson@nasa.gov

RELEASE: 11-408

NASA'S KEPLER CONFIRMS ITS FIRST PLANET IN HABITABLE ZONE OF SUN-LIKE STAR

MOFFET FIELD, Calif. -- NASA's Kepler mission has confirmed its first
planet in the "habitable zone," the region 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 the 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 California. "The more data we collect,
the keener our eye for finding the smallest planets out at longer
orbital periods."

For more information about the Kepler mission and to view the digital
press kit, visit:

http://www.nasa.gov/kepler