Invited Presentation

Dynamical Properties of Planetary Systems Formed by Giant Impacts

Author(s): Eiichiro Kokubo (National Astronomical Observatory of Japan)

Presenter: Eiichiro Kokubo (National Astronomical Observatory of Japan)

In the standard model of terrestrial planet formation in the solar system, terrestrial planets are spontaneously formed by giant impacts of protoplanets or planetary embryos after the dispersal of protoplanetary disk gas. Similar models are also proposed for the formation of close-in super-Earths mainly discovered by the Kepler transit observations. In this giant impact stage protoplanets gravitationally perturb and collide with each other to complete planets. We investigate the formation of planetary systems from protoplanet systems using N-body simulations. The goal of this study is to obtain the basic scaling laws for the orbital architecture of planetary systems and spin properties of planets formed by gravitational scattering and collision among protoplanets. We systematically change the system parameters of initial protoplanet systems such as the total mass, mean semimajor axis and angular momentum deficit and investigate their effects on final planetary systems. We find that the orbital architecture can be scaled by the Hill radius of planets and the ratio of the physical radius to the Hill radius. The mean eccentricity increases with the mean orbital separation of adjacent pairs and the final state is determined by the physical to Hill radius ratio. The spin axis distribution is isotropic and the spin angular velocity is slightly smaller than the critical spin angular velocity for rotational break-up.