NASA'S Kepler Mission Discovers Its First Rocky Planet
Kepler confirmed the discovery of its first rocky planet. Measuring 1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system.
NASA's Kepler mission confirmed the discovery of its first rocky planet, named
Kepler-10b. Measuring 1.4 times the size of Earth, it is the smallest planet
ever discovered outside our solar system.
The discovery of this
so-called exoplanet is based on more than eight months of data collected by the
spacecraft from May 2009 to early January 2010.
"All of Kepler's best
capabilities have converged to yield the first solid evidence of a rocky planet
orbiting a star other than our sun," said Natalie Batalha, Kepler's deputy
science team lead at NASA's Ames Research Center in Moffett Field, Calif., and
primary author of a paper on the discovery accepted by the Astrophysical
Journal. "The Kepler team made a commitment in 2010 about finding the telltale
signatures of small planets in the data, and it's beginning to pay
off."
Kepler's ultra-precise photometer measures the tiny decrease in a
star's brightness that occurs when a planet crosses in front of it. The size of
the planet can be derived from these periodic dips in brightness. The distance
between the planet and the star is calculated by measuring the time between
successive dips as the planet orbits the star.
Kepler is the first NASA
mission capable of finding Earth-size planets in or near the habitable zone, the
region in a planetary system where liquid water can exist on the planet's
surface. However, since it orbits once every 0.84 days, Kepler-10b is more than
20 times closer to its star than Mercury is to our sun and not in the habitable
zone.
Kepler-10 was the first star identified that could potentially
harbor a small transiting planet, placing it at the top of the list for
ground-based observations with the W.M. Keck Observatory 10-meter telescope in
Hawaii.
Scientists waiting for a signal to confirm Kepler-10b as a planet
were not disappointed. Keck was able to measure tiny changes in the star's
spectrum, called Doppler shifts, caused by the telltale tug exerted by the
orbiting planet on the star.
"The discovery of Kepler-10b, a bona fide
rocky world, is a significant milestone in the search for planets similar to our
own," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in
Washington. "Although this planet is not in the habitable zone, the exciting
find showcases the kinds of discoveries made possible by the mission and the
promise of many more to come," he said.
"Our knowledge of the planet is
only as good as the knowledge of the star it orbits," said Batalha. Because
Kepler-10 is one of the brighter stars being targeted by Kepler, scientists were
able to detect high frequency variations in the star's brightness generated by
stellar oscillations, or starquakes. "This is the analysis that really allowed
us to pin down Kepler-10b's properties.," she added.
"We have a clear
signal in the data arising from light waves that travel within the interior of
the star," said Hans Keldsen, an astronomer at the Kepler Asteroseismic Science
Consortium at Aarhus University in Denmark. Kepler Asteroseismic Science
Consortium scientists use the information to better understand the star, just as
earthquakes are used to learn about Earth's interior structure. "As a result of
this analysis, Kepler-10 is one of the most well characterized planet-hosting
stars in the universe next to our sun," Kjeldsen said.
That's good news
for the team studying Kepler-10b. Accurate stellar properties yield accurate
planet properties. In the case of Kepler-10b, the picture that emerges is of a
rocky planet with a mass 4.6 times that of Earth and with an average density of
8.8 grams per cubic centimeter -- similar to that of an iron
dumbbell.
"This planet is unequivocally rocky, with a surface you could
stand on," commented team member Dimitar Sasselov, of the Harvard-Smithsonian
Center for Astrophysics in Cambridge and a Kepler co-investigator.
"All
of Kepler’s best capabilities have converged for this discovery," Batalha said,
"yielding the first solid evidence of a rocky planet orbiting a star other than
our sun."
Ames 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.
