[en] We report the discovery of planet Kepler-12b (KOI-20), which at 1.695 ± 0.030 R [SUB]J[/SUB] is among the handful of planets with super-inflated radii above 1.65 R [SUB]J[/SUB]. Orbiting its slightly evolved G0 host with a 4.438 day period, this 0.431 ± 0.041 M [SUB]J[/SUB] planet is the least irradiated within this largest-planet-radius group, which has important implications for planetary physics. The planet's inflated radius and low mass lead to a very low density of 0.111 ± 0.010 g cm[SUP]-3[/SUP]. We detect the occultation of the planet at a significance of 3.7σ in the Kepler bandpass. This yields a geometric albedo of 0.14 ± 0.04; the planetary flux is due to a combination of scattered light and emitted thermal flux. We use multiple observations with Warm Spitzer to detect the occultation at 7σ and 4σ in the 3.6 and 4.5 μm bandpasses, respectively. The occultation photometry timing is consistent with a circular orbit at e < 0.01 (1σ) and e < 0.09 (3σ). The occultation detections across the three bands favor an atmospheric model with no dayside temperature inversion. The Kepler occultation detection provides significant leverage, but conclusions regarding temperature structure are preliminary, given our ignorance of opacity sources at optical wavelengths in hot Jupiter atmospheres. If Kepler-12b and HD 209458b, which intercept similar incident stellar fluxes, have the same heavy-element masses, the interior energy source needed to explain the large radius of Kepler-12b is three times larger than that of HD 209458b. This may suggest that more than one radius-inflation mechanism is at work for Kepler-12b or that it is less heavy-element rich than other transiting planets.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Fortney, Jonathan J; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA ; Alfred P. Sloan Research Fellow.
Demory, Brice-Olivier; Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Désert, Jean-Michel; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Rowe, Jason; SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
Marcy, Geoffrey W; Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
Isaacson, Howard; Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
Buchhave, Lars A; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA ; Niels Bohr Institute & StarPlan, University of Copenhagen, Copenhagen, Denmark
Ciardi, David; NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125, USA
Gautier, Thomas N; Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA 91109, USA
Batalha, Natalie M; Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192, USA
Caldwell, Douglas A; SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
Bryson, Stephen T; NASA Ames Research Center, Moffett Field, CA 94035, USA
Nutzman, Philip; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
Jenkins, Jon M; SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
Howard, Andrew; Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
Charbonneau, David; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Knutson, Heather A; Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
Howell, Steve B; NASA Ames Research Center, Moffett Field, CA 94035, USA
Everett, Mark; National Optical Astronomy Observatories, Tucson, AZ 85719, USA
Fressin, François; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Deming, Drake; Department of Astronomy, University of Maryland at College Park, College Park, MD 20742, USA
Borucki, William J; NASA Ames Research Center, Moffett Field, CA 94035, USA
Brown, Timothy M; Las Cumbres Observatory Global Telescope, Goleta, CA 93117, USA
Ford, Eric B; Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
Gilliland, Ronald L; Space Telescope Science Institute, Baltimore, MD 21218, USA
Latham, David W; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Miller, Neil; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
Seager, Sara; Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Fischer, Debra A; Department of Astronomy, Yale University, New Haven, CT 06520, USA
Koch, David; NASA Ames Research Center, Moffett Field, CA 94035, USA
Lissauer, Jack J; NASA Ames Research Center, Moffett Field, CA 94035, USA
Haas, Michael R; NASA Ames Research Center, Moffett Field, CA 94035, USA
Still, Martin; Bay Area Environmental Research Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
Lucas, Philip; Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Christiansen, Jessie L; SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
Geary, John C; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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