DISCOVERY AND ATMOSPHERIC CHARACTERIZATION OF GIANT PLANET KEPLER-12b: AN INFLATED RADIUS OUTLIER
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
- NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)
- Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA 91109 (United States)
- Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192 (United States)
- NASA Ames Research Center, Moffett Field, CA 94035 (United States)
- National Optical Astronomy Observatories, Tucson, AZ 85719 (United States)
We report the discovery of planet Kepler-12b (KOI-20), which at 1.695 {+-} 0.030 R{sub J} is among the handful of planets with super-inflated radii above 1.65 R{sub J}. Orbiting its slightly evolved G0 host with a 4.438 day period, this 0.431 {+-} 0.041 M{sub J} 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}. We detect the occultation of the planet at a significance of 3.7{sigma} 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 7{sigma} and 4{sigma} in the 3.6 and 4.5 {mu}m bandpasses, respectively. The occultation photometry timing is consistent with a circular orbit at e < 0.01 (1{sigma}) and e < 0.09 (3{sigma}). 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.
- OSTI ID:
- 22047363
- Journal Information:
- Astrophysical Journal, Supplement Series, Vol. 197, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0067-0049
- Country of Publication:
- United States
- Language:
- English
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