Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities
So Close and So Different
In our solar system, the rocky planets have very distinct orbits from those of the gas giants. Carter et al. (p. 556, published online 21 June) report on a planetary system where this pattern does not apply, posing a challenge to theories of planet formation. Data from the Kepler space telescope reveal two planets with radically different densities orbiting the same star with very similar orbital periods. One planet has a rocky Earth-like composition and the other is akin to Neptune.
Abstract
In the solar system, the planets’ compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets’ orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky “super-Earth,” whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.
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Supplementary Material
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Materials and Methods
Supplementary Text
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Volume 337 | Issue 6094
3 August 2012
3 August 2012
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Copyright © 2012, American Association for the Advancement of Science.
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Received: 12 April 2012
Accepted: 11 June 2012
Published in print: 3 August 2012
Acknowledgments
NASA’s Science Mission Directorate provided funding for the Kepler Discovery mission. J.A.C. and D.C.F. acknowledge support by NASA through Hubble Fellowship grants HF-51267.01-A and HF-51272.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, for NASA, under contract NAS 5-26555. E.A. acknowledges NSF Career grant AST-0645416 and thanks the Center for Astrophysics, where this work began. W.J.C., A.M., and Y.E. acknowledge the financial support of the UK Science and Technology Facilities Council (STFC). Funding for the Stellar Astrophysics Centre (SAC) is provided by the Danish National Research Foundation. The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (grant agreement no. 267864). S.H. acknowledges financial support from the Netherlands Organization for Scientific Research (NWO). Computational time on Kraken at the National Institute of Computational Sciences was provided through NSF TeraGrid allocation TG-AST090107. J.N.W. was supported by the NASA Kepler Participating Scientist program through grant NNX12AC76G. Refer to the supplementary materials for access information to data used in this work.
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