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NASA's Kepler Spacecraft Discovers its First Rocky Planet
01.14.11
 
NASA’s Kepler spacecraft has discovered Kepler-10b, its first confirmed rocky planet and the smallest transiting exoplanet discovered to date. 

Kepler-10b is only 1.4 times the size of Earth and has an average density of 8.8 grams per cubic centimeter, similar to that of an iron dumbbell. 

The planet orbits its star in only 0.84 days and is not in the habitable zone, where liquid water could exist.
 
Center Contact: Mike Mewhinney, 650-604-3937
HQ Contact: Trent Perrotto, 202-358-0321
For more info: www.nasa.gov/kepler

Natalie Batalha
Kepler Co-Investigator, San Jose State University

(:30) This rocky planet is not like any rocky planets in our own solar system.   It orbits its parent star with a period of less than one day…only point-8 days is what it takes to orbit the star once.  And because it’s so close to its parent star, the day side of that planet is scorching hot.  It’s about 1800 degrees Kelvin, which is hot enough to melt the rocks on the surface.   So the dayside of that planet is quite molten, we believe.
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(:23) The other thing that makes this such a special result is that we have all the best capabilities of Kepler converging on this one discovery.   We’ve got the very high precision photometry from the spacecraft, we’ve got the highest possible precision Doppler measurements from our ground-based telescopes and we’ve got the asteroseismic analysis, which allows us to pin down the properties of the star with very high precision.
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(:23) This discovery is a milestone not just for our team because it’s our first rocky planet, but it really is a milestone for humanity, in general, and for exoplanet studies.  There’s only one other object known to humanity, which is kind of in this regime that might be rocky.  But this is the first detection that really is unquestionably a rocky planet.


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Geoff Marcy
Kepler Co-Investigator, Univ. of California – Berkeley

(:34)  We measured the diameter of the planet by how much light is blocked as the planet blocks the starlight.  We measured the mass of the planet by how strongly the planet yanks on the host star.  And putting those two together, we learned the density of the planet.  This one planet, Kepler-10, has a density of eight grams per cubic centimeter.  The Earth, in comparison, is only 5.5 grams per cubic centimeter.  So you can see this Kepler-10 planet has a density greater than that of the Earth.   The Earth is obviously solid.  This other planet must be even denser.
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