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F. Marzari, M. Barbieri, P. Tricarico (Dip. di Fisica, Padova, Italy), H. Scholl (Obs. de Nice, Nice, France), P. Thebault (Obs. de Paris, Paris, France)
Due to the increased timespan of the exoplanet search, the number of extrasolar planets discovered far from their parent star has been increasing. At present, about 20 systems have a massive planet beyond 1.5 AU. In these systems, terrestrial planets may form in the inner regions where the preplanetary disk was possibly less perturbed by the massive planet. More complex systems, as 55 Cnc, may harbour terrestrial planets in between the giant planets. It is still matter of debate whether terrestrial planets may form after migration of a giant planet in an inside orbit. These scenarios have to be explored in detail also in view of future missions like DARWIN or TPF that will be able to observe only a limited number of extrasolar systems to find signatures of terrestrial planets.
With project ORESTE we intend to perform a detailed investigation of the formation process and orbital stability of terrestrial planets in those systems known to have a giant planet orbiting the star. The initial planetesimal accumulation phase will be studied with the code developed by Thebault et al. (2002). The code will allow us to estimate upper values of the relative velocities between planetesimals by including the effects of mutual collisions, the gravitational perturbation of the giant planet, and gas drag. If the velocities were low for a long fraction of the accretion history, then accumulation dominated over fragmentation and runaway growth was possible. The final starunaway growth, collide to form planets will be studied by direct numerical integrations of the embryos' orbits with the hybrid symplectic algorithm of Chambers (1999). Such calculations have been already performed for Epsilon Eridani and 47 UMa extrasolar systems by Thebault et al. (2002) and preliminary results are available for Gliese777. Once found that terrestrial planets can indeed form, we will study their long term stability with the FMA (Frequency Map Analysis) of Laskar (1993). Regions of stability as a function of the semimajor axis and initial eccentricity and inclination will be outlined.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.