An international team of astronomers has used nearly three years of high precision data from NASA's Kepler spacecraft to make the first observations of a planet outside our solar system that's about the size of the Earth's moon.
It is one of three planets orbiting a star designated Kepler-37 in the
Cygnus-Lyra region of the Milky Way. The three planets orbiting
Kepler-37 are smaller than the Earth while the third is twice Earth's
size. Kepler-37b is about 80% the size of Mercury and is the first
exoplanet to be found that is smaller than any planet in our own Solar System. Astronomers with the Kepler team are looking for earth-like planets that might be able to support life.
"That's basically listening to the star by measuring sound waves," said Steve Kawaler, an Iowa State University
professor of physics and astronomy, was part of a team of researchers
who studied the oscillations of Kepler-37 to determine its size."The
bigger the star, the lower the frequency, or 'pitch' of its song."
The team determined Kepler-37's mass is about 80 percent the mass of
our sun. That's the lowest mass star astronomers have been able to
measure using oscillation data for an ordinary star. Those measurements
also allowed the main research team to more accurately measure the three
planets orbiting Kepler-37, including the tiny Kepler-37b.
"Owing to its extremely small size, similar to that of the Earth's
moon, and highly irradiated surface, Kepler-37b is very likely a rocky
planet with no atmosphere or water, similar to Mercury," the astronomers
wrote in a summary of their findings. "The detection of such a small
planet shows for the first time that stellar systems host planets much
smaller as well as much larger than anything we see in our own Solar
System." Kawaler said the discovery is exciting because of what it says
about the Kepler Mission's capabilities to discover new planetary
systems around other stars.
Kepler launched March 6, 2009, from Florida's Cape Canaveral Air
Force Station. The spacecraft is orbiting the sun carrying a photometer,
or light meter, to measure changes in the brightness of thousands of
stars. Its primary job is to detect tiny variations in the brightness of
the stars within its view to indicate planets passing in front of the
star.
The Kepler Asteroseismic Investigation is also using data from that
photometer to study stars. The investigation is led by a four-member
steering committee: Kawaler, Chair Ron Gilliland of the Space Telescope
Science Institute based in Baltimore, Jorgen Christensen-Dalsgaard and Hans Kjeldsen, both of Aarhus University in Denmark.
Kawaler said Kepler is sending astronomers photometry data that's
"probably the best we'll see in our lifetimes." This latest discovery
shows astronomers "we have a proven technology for finding small planets
around other stars." That could have implications for some big-picture
discoveries: "While a sample of only one planet is too small to use for
determination of occurrence rates," the astronomers write in the Nature paper, "it does lend weight to the belief that planet occurrence increases exponentially with decreasing planet size."
The findings are published were published online on Feb. 20 by the journal Nature. The lead authors are Thomas Barclay of the NASA Ames Research Center
in California and the Bay Area Environmental Research Institute and
Jason Rowe of NASA Ames and the SETI Institute in California.
For more information: Paper: dx.doi.org/10.1038/nature11914 Journal reference: Nature
Source: The Daily Galaxy via Iowa State University and Nature
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