[Vision2020] 4-18-13: NASA's Kepler Discovers Its Smallest 'Habitable Zone' Planets to Date

[Ted Moffett]

http://www.nasa.gov/mission_pages/kepler/news/kepler-62-kepler-69.html

MOFFETT FIELD, Calif. -- 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 and to view the digital press
kit, visit:

*http://www.nasa.gov/kepler*------------------------------------------
Vision2020 Post: Ted Moffett
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