Orbital migration of giant planets: Using numerical integration to investigate consequences for other bodies

A number of extrasolar planets have been detected in close orbits around ne arby stars. It is probable that these planets did not form in these orbits but migrated from their formation locations beyond the ice line. Orbital mi gration mechanisms involving angular momentum transfer through tidal intera ctions between the planets and circumstellar gas-dust disks or by gravitati onal interaction with a residual planetesimal disk together with several me ans of halting inward migration have been identified. These offer plausible schemes to explain the orbits of observed extrasolar giant planets and gia nt planets within the Solar System. Recent advances in numerical integratio n methods and in the power of computer workstations have allowed these tech niques to be applied to modelling directly the mechanisms and consequences of orbital migration in the Solar System. There is now potential for these techniques also to be applied to modelling the consequences of the orbital migration of planets in the observed exoplanetary systems. In particular th e detailed investigation of the stability of terrestrial planets in the hab itable zone of these systems and the formation of terrestrial planets after the dissipation of the gas disk is now possible. The stability of terrestr ial planets in the habitable zone of selected exoplanetary systems has been established and the possibility of the accretion of terrestrial planets in these systems is being investigated by the author in collaboration with Ba rrie W. Jones (Open University), and with John Chambers (NASA-Ames) and Mar k Bailey of Armagh Observatory, using numerical integration. The direct sim ulation of orbital migration by planetesimal scattering must probably await faster hardware and/or more efficient algorithms.