NASA's Kepler Mission Discovers Two Planets Transiting Same Star

WASHINGTON -- NASA's Kepler spacecraft has discovered the first
confirmed planetary system with more than one planet crossing in
front of, or transiting, the same star.

The transit signatures of two distinct planets were seen in the data
for the sun-like star designated Kepler-9. The planets were named
Kepler-9b and 9c. The discovery incorporates seven months of
observations of more than 156,000 stars as part of an ongoing search
for Earth-sized planets outside our solar system. The findings will
be published in Thursday's issue of the journal Science.

Kepler's ultra-precise camera measures tiny decreases in the stars'
brightness that occur when a planet transits them. The size of the
planet can be derived from these temporary dips.

The distance of the planet from the star can be calculated by
measuring the time between successive dips as the planet orbits the
star. Small variations in the regularity of these dips can be used to
determine the masses of planets and detect other non-transiting
planets in the system.

In June, mission scientists submitted findings for peer review that
identified more than 700 planet candidates in the first 43 days of
Kepler data. The data included five additional candidate systems that
appear to exhibit more than one transiting planet. The Kepler team
recently identified a sixth target exhibiting multiple transits and
accumulated enough follow-up data to confirm this multi-planet system.

"Kepler's high quality data and round-the-clock coverage of transiting
objects enable a whole host of unique measurements to be made of the
parent stars and their planetary systems," said Doug Hudgins, the
Kepler program scientist at NASA Headquarters in Washington.

Scientists refined the estimates of the masses of the planets using
observations from the W.M. Keck Observatory in Hawaii. The
observations show Kepler-9b is the larger of the two planets, and
both have masses similar to but less than Saturn. Kepler-9b lies
closest to the star with an orbit of about 19 days, while Kepler-9c
has an orbit of about 38 days. By observing several transits by each
planet over the seven months of data, the time between successive
transits could be analyzed.

"This discovery is the first clear detection of significant changes in
the intervals from one planetary transit to the next, what we call
transit timing variations," said Matthew Holman, a Kepler mission
scientist from the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Mass. "This is evidence of the gravitational interaction
between the two planets as seen by the Kepler spacecraft."

In addition to the two confirmed giant planets, Kepler scientists also
have identified what appears to be a third, much smaller transit
signature in the observations of Kepler-9. That signature is
consistent with the transits of a super-Earth-sized planet about 1.5
times the radius of Earth in a scorching, near-sun 1.6 day-orbit.
Additional observations are required to determine whether this signal
is indeed a planet or an astronomical phenomenon that mimics the
appearance of a transit.

NASA's Ames Research Center in Moffett Field, Calif., 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.

For more information about the Kepler mission, visit:

http://www.nasa.gov/kepler

Source: NASA