The Formation of Compact Planetary Systems

Among it's many achievements, NASA's Kepler Space Telescope has demonstrated the prevalence of short period planets. It is expected that as many as half of sun-like stars host planets with periods shorter than 200 days and this fraction may be even larger for lower mass stars. The formation of these systems remains a matter of debate. Either these planets form farther away from their star and migrate inwards due to interactions with the protoplanetary disk or they form at or near their current orbits. This thesis investigates the process of planet formation in the inner disk, from start to end, beginning with a model in which the planetesimal disk is built up from the accretion of inward drifting pebbles (small, cm-sized bodies that form in the outer disk). This process tends to form massive planetesimal disks and builds them from the inside out such that the extent of pebble delivery determines the final surface density profile of the disk. Therefore, anything that affects the rate or duration of pebble delivery to the inner disk, e.g. protoplanetary disk metallicity or mass, will affect the surface density distribution of the planetesimal disk. A comparison of the planetary systems that form in N-body simulations of in-situ planet formation to the Kepler sample indicates that some variation in planetesimal disk structure is needed to reproduce the range of observed system architectures and that a relatively massive disk is required. The similarity and variety of planetesimal disk structures implied by both the pebble accretion and late-stage planet formation results suggest a self consistent model in which the observed diversity of planetary systems is a consequence of the expected variations in protoplanetary disk metallicity and/or total mass. Further simulations, using the final conditions of pebble accretion simulations as the initial conditions to late-stage planet formation simulations, find that such a model can reproduce many observable characteristics of Kepler detected exoplanets.