Feb. 20, 2013
Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov
Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-4789
michele.johnson@nasa.gov
RELEASE: 13-057
NASA'S KEPLER MISSION DISCOVERS TINY PLANET SYSTEM
WASHINGTON -- NASA's Kepler mission scientists have discovered a new
planetary system that is home to the smallest planet yet found around
a star similar to our sun.
The planets are located in a system called Kepler-37, about 210
light-years from Earth in the constellation Lyra. The smallest
planet, Kepler-37b, is slightly larger than our moon, measuring about
one-third the size of Earth. It is smaller than Mercury, which made
its detection a challenge.
The moon-size planet and its two companion planets were found by
scientists with NASA's Kepler mission to find Earth-sized planets in
or near the "habitable zone," the region in a planetary system where
liquid water might exist on the surface of an orbiting planet.
However, while the star in Kepler-37 may be similar to our sun, the
system appears quite unlike the solar system in which we live.
Astronomers think Kepler-37b does not have an atmosphere and cannot
support life as we know it. The tiny planet almost certainly is rocky
in composition. Kepler-37c, the closer neighboring planet, is
slightly smaller than Venus, measuring almost three-quarters the size
of Earth. Kepler-37d, the farther planet, is twice the size of Earth.
The first exoplanets found to orbit a normal star were giants. As
technologies have advanced, smaller and smaller planets have been
found, and Kepler has shown even Earth-size exoplanets are common.
"Even Kepler can only detect such a tiny world around the brightest
stars it observes," said Jack Lissauer, a planetary scientist at
NASA's Ames Research Center in Moffett Field, Calif. "The fact we've
discovered tiny Kepler-37b suggests such little planets are common,
and more planetary wonders await as we continue to gather and analyze
additional data."
Kepler-37's host star belongs to the same class as our sun, although
it is slightly cooler and smaller. All three planets orbit the star
at less than the distance Mercury is to the sun, suggesting they are
very hot, inhospitable worlds. Kepler-37b orbits every 13 days at
less than one-third Mercury's distance from the sun. The estimated
surface temperature of this smoldering planet, at more than 800
degrees Fahrenheit (700 degrees Kelvin), would be hot enough to melt
the zinc in a penny. Kepler-37c and Kepler-37d, orbit every 21 days
and 40 days, respectively.
"We uncovered a planet smaller than any in our solar system orbiting
one of the few stars that is both bright and quiet, where signal
detection was possible," said Thomas Barclay, Kepler scientist at the
Bay Area Environmental Research Institute in Sonoma, Calif., and lead
author of the new study published in the journal Nature. "This
discovery shows close-in planets can be smaller, as well as much
larger, than planets orbiting our sun."
The research team used data from NASA's Kepler space telescope, which
simultaneously and continuously measures the brightness of more than
150,000 stars every 30 minutes. 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. This causes a dip in
the brightness of the starlight that reveals the transiting planet's
size relative to its star.
The size of the star must be known in order to measure the planet's
size accurately. To learn more about the properties of the star
Kepler-37, scientists examined sound waves generated by the boiling
motion beneath the surface of the star. They probed the interior
structure of Kepler-37's star just as geologists use seismic waves
generated by earthquakes to probe the interior structure of Earth.
The science is called asteroseismology.
The sound waves travel into the star and bring information back up to
the surface. The waves cause oscillations that Kepler observes as a
rapid flickering of the star's brightness. Like bells in a steeple,
small stars ring at high tones while larger stars boom in lower
tones. The barely discernible, high-frequency oscillations in the
brightness of small stars are the most difficult to measure. This is
why most objects previously subjected to asteroseismic analysis are
larger than the sun.
With the very high precision of the Kepler instrument, astronomers
have reached a new milestone. The star Kepler-37, with a radius just
three-quarters of the sun, now is the smallest bell in the
asteroseismology steeple. The radius of the star is known to 3
percent accuracy, which translates to exceptional accuracy in the
planet's size.
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 tenth Discovery
Mission and was 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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