NASA's Kepler Discovers Multiple Planets Orbiting a Pair of Stars

Aug. 28, 2012

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: 12-298

NASA'S KEPLER DISCOVERS MULTIPLE PLANETS ORBITING A PAIR OF STARS

NASA's Kepler mission has discovered multiple transiting planets
orbiting two suns for the first time. The system, known as a
circumbinary planetary system, is 4,900 light-years from Earth in the
constellation Cygnus.

Coming less than a year after the announcement of the first
circumbinary planet, Kepler-16b, this discovery proves that more than
one planet can form and persist in the stressful realm of a binary
star. The discovery demonstrates the diversity of planetary systems
in our galaxy.

Astronomers detected two planets in the Kepler-47 system, a pair of
orbiting stars that eclipse each other every 7.5 days from our
vantage point on Earth. One star is similar to the sun in size, but
only 84 percent as bright. The second star is diminutive, measuring
only one-third the size of the sun and less than 1 percent as bright.


"In contrast to a single planet orbiting a single star, the planet in
a circumbinary system must transit a 'moving target.' As a
consequence, time intervals between the transits and their durations
can vary substantially, sometimes short, other times long," said
Jerome Orosz, associate professor of astronomy at San Diego State
University and lead author of the paper. "The intervals were the
telltale sign these planets are in circumbinary orbits."

The inner planet, Kepler-47b, orbits the pair of stars in less than 50
days. While it cannot be directly viewed, it is thought to be a
sweltering world, where the destruction of methane in its
super-heated atmosphere might lead to a thick haze that could blanket
the planet. At three times the radius of Earth, Kepler-47b is the
smallest known transiting circumbinary planet.

The outer planet, Kepler-47c, orbits its host pair every 303 days,
placing it in the so-called "habitable zone," the region in a
planetary system where liquid water might exist on the surface of a
planet. While not a world hospitable for life, Kepler-47c is thought
to be a gaseous giant slightly larger than Neptune, where an
atmosphere of thick bright water-vapor clouds might exist.

"Unlike our sun, many stars are part of multiple-star systems where
two or more stars orbit one another. The question always has been --
do they have planets and planetary systems? This Kepler discovery
proves that they do," said William Borucki, Kepler mission principal
investigator at NASA's Ames Research Center in Moffett Field, Calif.
"In our search for habitable planets, we have found more
opportunities for life to exist."

To search for transiting planets, the research team used data from the
Kepler space telescope, which measures dips in the brightness of more
than 150,000 stars. Additional ground-based spectroscopic
observations using telescopes at the McDonald Observatory at the
University of Texas at Austin helped characterize the stellar
properties. The findings are published in the journal Science.

"The presence of a full-fledged circumbinary planetary system orbiting
Kepler-47 is an amazing discovery," said Greg Laughlin, professor of
Astrophysics and Planetary Science at the University of California in
Santa Cruz. "These planets are very difficult to form using the
currently accepted paradigm, and I believe that theorists, myself
included, will be going back to the drawing board to try to improve
our understanding of how planets are assembled in dusty circumbinary
disks."

Ames manages Kepler's ground system development, mission operations
and science data analysis. NASA's Jet Propulsion Laboratory in
Pasadena, Calif., managed the 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 tenth Discovery
Mission and funded by NASA's Science Mission Directorate at the
agency's headquarters in Washington.

For more information about the Kepler mission, visit:

http://www.nasa.gov/kepler


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