Andrews, M.B.; (2009) The influence of a migrating planet on the topology and chemistry of a protoplanetary disc. Doctoral thesis , UCL (University College London).

Abstract

One of the surprising discoveries in the field of extrasolar planets is the proliferation of massive planets in small orbits. It is not believed possible for these planets to form in situ. Instead, it is likely that they formed at much greater distances from their parent stars, beyond the radial distance where the disc temperature drops to below the ice condensation temperature. The inevitable migration that is necessary to transport large planets to greatly reduced orbits has been demonstrated as possible through disc-planet simulations. This migration takes the planet through the ‘terrestrial’ planet forming zone during the period when the terrestrial-planet building blocks, planetesimals, swarm the region. The first part of this thesis considers the effects of planet migration on the orbital dynamics of the planetesimals in the terrestrial zone, how the planetesimals are accreted, shepherded and possibly scattered outwards, and whether enough material survives in the terrestrial zone from which to form terrestrial planets. The orbital eccentricity excitation of the planetesimals results in orbits that inevitably cross. The differential velocity component may result in catastrophic collisions between planetesimals, releasing significant amounts of dust back into the disc. The effect of dust replenishment on the ionisation fraction of the disc and the ability to support MHD turbulence requires knowledge of the physical and chemical environment of the disc. The second part of this thesis considers the chemical evolution of a molecular cloud undergoing gravitational collapse and warm-up to derive chemical abundances applicable to disc modelling. The final part of this thesis investigates the possibility of dust replenishment in the disc due to the induced catastrophic collisions between planetesimals. The potential dust replenishment combined with the derived chemical abundances are input into a chemical disc model to assess the influence of a migrating planet on a protoplanetary disc.

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