The high albedo of the hot Jupiter Kepler-7b

Brice Olivier Demory, Sara Seager, Nikku Madhusudhan, Hans Kjeldsen, Jørgen Christensen-Dalsgaard, Michal Gillon, Jason F. Rowe, William F. Welsh, Elisabeth R. Adams, Andrea Dupree, Donald W Mccarthy, Craig Kulesa, William J. Borucki, David G. Koch

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62 Scopus citations

Abstract

Hot Jupiters are expected to be dark from both observations (albedo upper limits) and theory (alkali metals and/or TiO and VO absorption). However, only a handful of hot Jupiters have been observed with high enough photometric precision at visible wavelengths to investigate these expectations. The NASA Kepler mission provides a means to widen the sample and to assess the extent to which hot Jupiter albedos are low. We present a global analysis of Kepler-7b based on Q0-Q4 data, published radial velocities, and asteroseismology constraints. We measure an occultation depth in the Kepler bandpass of 44 ± 5 ppm. If directly related to the albedo, this translates to a Kepler geometric albedo of 0.32 ± 0.03, the most precise value measured so far for an exoplanet. We also characterize the planetary orbital phase light curve with an amplitude of 42 ± 4 ppm. Using atmospheric models, we find it unlikely that the high albedo is due to a dominant thermal component and propose two solutions to explain the observed planetary flux. First, we interpret the Kepler-7b albedo as resulting from an excess reflection over what can be explained solely by Rayleigh scattering, along with a nominal thermal component. This excess reflection might indicate the presence of a cloud or haze layer in the atmosphere, motivating new modeling and observational efforts. Alternatively, the albedo can be explained by Rayleigh scattering alone if Na and K are depleted in the atmosphere by a factor of 10-100 below solar abundances.

Original languageEnglish (US)
Article numberL12
JournalAstrophysical Journal Letters
Volume735
Issue number1
DOIs
Publication statusPublished - Jul 1 2011

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Keywords

  • planetary systems
  • stars: individual (Kepler-7, KIC 5780885, 2MASS 19141956+4105233)
  • techniques: photometric

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Demory, B. O., Seager, S., Madhusudhan, N., Kjeldsen, H., Christensen-Dalsgaard, J., Gillon, M., ... Koch, D. G. (2011). The high albedo of the hot Jupiter Kepler-7b. Astrophysical Journal Letters, 735(1), [L12]. https://doi.org/10.1088/2041-8205/735/1/L12