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-7 b based on Q0-Q4 data , published radial velocities , and asteroseismology constraints .
We measure an occultation depth in the Kepler bandpass of 44 \pm 5 ppm .
If directly related to the albedo , this translates to a Kepler geometric albedo of 0.32 \pm 0.03 , the most precise value measured so far for an exoplanet .
We also characterize the planetary orbital phase lightcurve with an amplitude of 42 \pm 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 .
Firstly , we interpret the Kepler-7 b 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 .