Known exoplanet HAT-P-7 studied: secondary eclipse and reflected starlight readily detected / Already something learned about planet's atmosphere / Exo-Earths clearly within reach, but wait til 2012, please!

At a news conference on August 6 NASA finally revealed the first lightcurve of a star measured by the Kepler satellite launched in March (see Update #325): Its noise level is about a factor 100 lower than a typical groundbased lightcurve. (A comparision with a typical result from the CoRoT spacecraft would have been nice but it was not mentioned once.)

In a nutshell this means that Kepler is working as advertised and will be able to detect Earth-size planets of other stars if they exist, though the actual measurements and groundbased follow-up observations won't be done until the year 2012.

The lightcurve shown is of the star HAT-P-7 which was known to have a transiting planet: the secondary eclipse (planet goes behind star) is also evident in the Kepler lightcurve as is a general brightening of the combined light of star and planet before and after transit: Here the starlight reflected by the planet's atmosphere is contributing to the signal. From this effect alone something can already be learned about HAT-P-7b's atmosphere, namely that there must be a layer with absorbing particles. A few more hard figures but little else can be found in a 1-page paper in Science of Aug. 7.

You can find Daniel Fischers Cosmic Mirror here.