Two Earth-sized planets orbiting Kepler-20
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Seager_Two Earth-sized.pdf
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615.61 KB
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Adobe PDF
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48037bb87de3d1c690566d16337c60d7
Author(s)
Seager, Sara
Rogers, Leslie Anne
Date Issued
December 2011
Journal
Nature
Publisher
Nature Publishing Group
Citation
Fressin, Francois et al. “Two Earth-sized Planets Orbiting Kepler-20.” Nature 482.7384 (2011): 195–198.
Version
Author's final manuscript
Abstract
Since the discovery of the first extrasolar giant planets around Sun-like stars[superscript 1, 2], evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered[superscript 3] has a radius 1.42 times that of the Earth’s radius (R[subscript ⊕]), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R[subscript ⊕]) and the other smaller than the Earth (0.87R[subscript ⊕]), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets4. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Department of Physics
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1038/nature10780
