Extrasolar planets, or exoplanets, are planets orbiting around other stars.
We know these planets since about 25 years and
have found roughly 2000 until now.
I write in detail about exoplanets in my blog, so feel free to take a look.
exoplanet blog »
My work on exoplanets is not so much concerned with their detection.
I rather try to characterize them in more detail or use them to learn something about
the planetary system they are in or the host stars they orbit.
One example is the transit mapping technique, which is basically explained in the
previous subpage on starspots.
A transiting planet can be used to resolve the surface of the star and study the
spots, the spot distribution, and its evolution in time.
This is something we did in detail for CoRoT-2.
What you see in the map on the right is the part of the stellar surface of CoRoT-2
that is transited by the planet CoRoT-2 b.
Black areas are parts of the surface with a higher spot coverage, yello or white
areas have very few or no spots.
Since the observations of CoRoT-2 span half a year, this map tracks the evolution of the
surface over half a year and shows how the spot distribution is changing.
Doing something like this was only possible because of the fantastic data coming from
CoRoT or Kepler.
Other examples of what research I do on exoplanets are the investigation of
limb darkening using high-precision transit lightcurves, flares in CoRoT
and Kepler photometry, and detailed analyses of radial velocity measurements.
A neat example of the latter was showing the
chromosphere of CoRoT-2
using the Rossiter-McLaughlin effect.
The Rossiter-McLaughlin effect is an apparent shift of the spectrum
of a star when a planet transits its surface.
This is usually something observed in spectral lines coming from the photosphere,
the visible surface of the star.
However, in the plot on the right you can see how this looks like for the
chromosphere of CoRoT-2, the stellar atmospheric layer above the photosphere.
From these observations we can learn that the radius of the star in the
chromosphere is about 16 % larger than the photometric radius,
a measurement that is hardly possible with any other mehtod