The eccentricity distribution of massive extrasolar planets has a median near e=0.2, higher than expected from the planet formation process. A successful route to reproduce the observed eccentricities via purely gravitational dynamics is to begin with unstable initial conditions, with planets spaced closely enough that gravitational interactions lead to crossing orbits, collisions, and ejections of some of the planets. If the natal disk is still present when the scattering occurs, it could potentially alter the outcome of planet-planet scattering. This is the focus of the paper ‘Hydrodynamic outcomes of planet scattering in transitional discs’, Moeckel and Armitage, 2011.
The animations below show some results from 2D hydrodynamic simulations of planetary scattering taking place in an embedding disc. This example shows a three body resonant chain. After a brief gap-opening phase of the system’s evolution, the planets are trapped into a 6:3:2 mean motion resonance, protecting them from scattering despite the crossing orbits that develop. Each resonant pair is highlighted in the movie. The end of the animation moves into a frame precessing at the same rate as the inner orbit. While we don’t show the photoevaporative clearing in its entirety here, the planets remain in the same configuration through the clearing phase and for at least 50 Myr of purely gravitational dynamics.