April 18, 2013
J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-4789
michele.johnson@nasa.gov
RELEASE: 13-112
NASA'S KEPLER DISCOVERS ITS SMALLEST 'HABITABLE ZONE' PLANETS TO DATE
WASHINGTON -- NASA's Kepler mission has discovered two new planetary
systems that include three super-Earth-size planets in the "habitable
zone," the range of distance from a star where the surface
temperature of an orbiting planet might be suitable for liquid water.
The Kepler-62 system has five planets; 62b, 62c, 62d, 62e and 62f. The
Kepler-69 system has two planets; 69b and 69c. Kepler-62e, 62f and
69c are the super-Earth-sized planets.
Two of the newly discovered planets orbit a star smaller and cooler
than the sun. Kepler-62f is only 40 percent larger than Earth, making
it the exoplanet closest to the size of our planet known in the
habitable zone of another star. Kepler-62f is likely to have a rocky
composition. Kepler-62e, orbits on the inner edge of the habitable
zone and is roughly 60 percent larger than Earth.
The third planet, Kepler-69c, is 70 percent larger than the size of
Earth, and orbits in the habitable zone of a star similar to our sun.
Astronomers are uncertain about the composition of Kepler-69c, but
its orbit of 242 days around a sun-like star resembles that of our
neighboring planet Venus.
Scientists do not know whether life could exist on the newfound
planets, but their discovery signals we are another step closer to
finding a world similar to Earth around a star like our sun.
"The Kepler spacecraft has certainly turned out to be a rock star of
science," said John Grunsfeld, associate administrator of the Science
Mission Directorate at NASA Headquarters in Washington. "The
discovery of these rocky planets in the habitable zone brings us a
bit closer to finding a place like home. It is only a matter of time
before we know if the galaxy is home to a multitude of planets like
Earth, or if we are a rarity."
The Kepler space telescope, which simultaneously and continuously
measures the brightness of more than 150,000 stars, is NASA's first
mission capable of detecting Earth-size planets around stars like our
sun.
Orbiting its star every 122 days, Kepler-62e was the first of these
habitable zone planets identified. Kepler-62f, with an orbital period
of 267 days, was later found by Eric Agol, associate professor of
astronomy at the University of Washington and co-author of a paper on
the discoveries published in the journal Science.
The size of Kepler-62f is now measured, but its mass and composition
are not. However, based on previous studies of rocky exoplanets
similar in size, scientists are able to estimate its mass by
association.
"The detection and confirmation of planets is an enormously
collaborative effort of talent and resources, and requires expertise
from across the scientific community to produce these tremendous
results," said William Borucki, Kepler science principal investigator
at NASA's Ames Research Center at Moffett Field, Calif., and lead
author of the Kepler-62 system paper in Science. "Kepler has brought
a resurgence of astronomical discoveries and we are making excellent
progress toward determining if planets like ours are the exception or
the rule."
The two habitable zone worlds orbiting Kepler-62 have three companions
in orbits closer to their star, two larger than the size of Earth and
one about the size of Mars. Kepler-62b, Kepler-62c and Kepler-62d,
orbit every five, 12, and 18 days, respectively, making them very hot
and inhospitable for life as we know it.
The five planets of the Kepler-62 system orbit a star classified as a
K2 dwarf, measuring just two-thirds the size of the sun and only
one-fifth as bright. At seven billion years old, the star is somewhat
older than the sun. It is about 1,200 light-years from Earth in the
constellation Lyra.
A companion to Kepler 69c, known as Kepler 69b, is more than twice the
size of Earth and whizzes around its star every 13 days. The
Kepler-69 planets' host star belongs to the same class as our sun,
called G-type. It is 93 percent the size of the sun and 80 percent as
luminous and is located approximately 2,700 light-years from Earth in
the constellation Cygnus.
"We only know of one star that hosts a planet with life, the sun.
Finding a planet in the habitable zone around a star like our sun is
a significant milestone toward finding truly Earth-like planets,"
said Thomas Barclay, Kepler scientist at the Bay Area Environmental
Research Institute in Sonoma, Calif., and lead author of the
Kepler-69 system discovery published in the Astrophysical Journal.
When a planet candidate transits, or passes in front of the star from
the spacecraft's vantage point, a percentage of light from the star
is blocked. The resulting dip in the brightness of the starlight
reveals the transiting planet's size relative to its star. Using the
transit method, Kepler has detected 2,740 candidates. Using various
analysis techniques, ground telescopes and other space assets, 122
planets have been confirmed.
Early in the mission, the Kepler telescope primarily found large,
gaseous giants in very close orbits of their stars. Known as "hot
Jupiters," these are easier to detect due to their size and very
short orbital periods. Earth would take three years to accomplish the
three transits required to be accepted as a planet candidate. As
Kepler continues to observe, transit signals of habitable zone
planets the size of Earth orbiting stars like the sun will begin to
emerge.
Ames is responsible for 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 & 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 Kepler science data. Kepler is NASA's 10th Discovery
Mission and was funded by the agency's Science Mission Directorate.
For more information about the Kepler mission, visit:
http://www.nasa.gov/kepler
-end-
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