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Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star

Borucki, William J. and Ciardi, David and Howard, Andrew W. (2012) Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star. Astrophysical Journal, 745 (2). Art. No. 120. ISSN 0004-637X.

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A search of the time-series photometry from NASA's Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 ± 0.060 M_☉ and 0.979 ± 0.020 R_☉. The depth of 492 ± 10 ppm for the three observed transits yields a radius of 2.38 ± 0.13 Re for the planet. The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion. A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits. The final validation of the planet is provided by 16 radial velocities (RVs) obtained with the High Resolution Echelle Spectrometer on Keck I over a one-year span. Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3σ upper limit of 124 M_⊕, safely in the regime of planetary masses, thus earning the designation Kepler-22b. The radiative equilibrium temperature is 262 K for a planet in Kepler-22b's orbit. Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the habitable zone of any star other than the Sun.

Item Type:Article
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URLURL TypeDescription
Ciardi, David0000-0002-5741-3047
Howard, Andrew W.0000-0001-8638-0320
Additional Information:© 2011 American Astronomical Society. Received 2011 November 18; accepted 2011 November 29; published 2012 January 6. Kepler was competitively selected as the tenth Discovery mission. Funding for this mission is provided by NASA’s Science Mission Directorate. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Some of the observations were made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Additional support for this work was also received from National Center for Atmospheric Research which is sponsored by the National Science Foundation. The authors thank the many people who gave so generously of their time to make this Mission a success. S.H. acknowledges financial support from the Netherlands Organisation for Scientific Research (NWO).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
National Center for Atmospheric Research (NCAR)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Subject Keywords:planetary systems; stars: fundamental parameters; stars: individual (Kepler-22, KIC 10593626)
Issue or Number:2
Record Number:CaltechAUTHORS:20120319-080521629
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Official Citation:Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star William J. Borucki et al. 2012 ApJ 745 120
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29762
Deposited By: Ruth Sustaita
Deposited On:19 Mar 2012 16:39
Last Modified:03 Oct 2019 03:44

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