Dynamical Stability in the Habitable Zones of Nearby Extrasolar Planetary Systems

Discoveries of super-Earths raise our hopes to find terrestrial planets moving in the habitable zone (HZ) of Sun-like stars. In the near future astronomers will try to find such an "exo-Earth" orbiting within the HZ of other stars having various ground-based and space missions (e.g., CoRoT, Kepler, Gaia) at their disposal. It is well known, that the evolution of a biosphere is a process covering stellar timescales, therefore one of the basic requirements for habitability is the long-term orbital stability of planets in the HZ. This investigation tackles the dynamical stability of potential additional terrestrial planets in nearby (within 30 pc) extrasolar planetary systems. Global studies do exist, that provide stability maps for systems consisting of a star, a gas giant and mass-less test-planets, e.g., the so-called "Exocatalogue" (see http: //astro.elte.hu/exocatalogue/). Additionally we provide the tool "ExoStab" (see http://www.univie.ac.at/adg/exostab/), which allows a more interactive application of the Exocatalogue data. Utilities like these are used to verify the long-term stability of an additional low-mass planet moving in a particular single-star single-planet system. A comparison of the results of numerical simulations including also massive test-planets with the Exocatalogue will be shown. Since some orbital elements, like e.g., the orbital eccentricities, the mass of the gas giant or its semi-major axis are afflicted with errors, we will also perform a parameter study, to ensure the validity of our results.