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| Titel |
The Strange Case of Corot-7b |
| VerfasserIn |
Ruth Ziethe, Peter Wurz, Helmut Lammer |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033039
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| Zusammenfassung |
| The discovery of extrasolar planets - planets that orbit stars other than our sun - has always
been fascinating. Meanwhile more than 400 so–called exoplanets have been detected. These
discoveries provide us with the opportunity to gain a better understanding of our
own solar system. However, most of the detected exoplanets so far are relatively
large (beyond 10 MEarth) and can be regarded as gaseous planets, which allow
comparisons with the gas giants in our solar system. Scientists have always seeked after
smaller and rocky planets, which could be compared to Earth or other earth–like
bodies.
Recently, the COROT mission discovered an object, Corot-7b, with a radius of only
1.68 REarth corresponding to a mass of 4.8 ± 0.8 MEarth. This first low-mass
exoplanet – a so-called ’Super-Earth’ – can be considered to be solid. Although still
rather large it is much more similar to the solid planets in our solar system than
the other discoveries before. Corot-7b orbits its primary at a very close distance
and is therefore tidally locked in an 1:1 spin-orbit resonance. This implies a very
inhomogeneous energy input from the star into the planet. Since the dayside is
constantly exposed to the star, there is a strong temperature gradient towards the
nightside. The surface temperature on the illuminated side is estimated with 2700 K,
while the shadowed side is thought to be at 110 K. The high temperatures on the
dayside will cause the evaporation of volatiles, which gives rise to the formation of an
atmosphere.
We introduce a three dimensional thermal convection model by solving the pertaining
dimensionless hydrodynamical equations, derived from the conservation of mass, momentum
and energy. With the code we compute the temperature field T(r,Ï,φ), by employing a
combination of a spectral and a finite difference method. We are especially looking at the
formation of partially molten regions due to the inhomogeneous energy input onto the
surface. The temperature of the surface and subsurface regions is enormously important for
the composition of the atmosphere fed from volatiles, which escaped from the planet. The
atmosphere is the only part of this exoplanet which can be observed with remote sensing
methods. Henceforth, understanding the conditions for the formation of an atmosphere (i.e.,
surface temperature map) is an important step forward in understanding extrasolar planets. |
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