Numerical Studies in the Formation of Planetary Systems: What We Can Learn from Inclinations and Angular Momenta

Abstract

This thesis presents numerical work performed to answer a few targeted questions in planet formation theory, applied both to specific systems and more generally. To put these questions in context, it begins with a broad overview of the current state of the field of planet formation, as motivated by observations both within and outside the Solar System. From there, in Chapters 2 and 3, I turn to the study of two particular systems of interest, the TRAPPIST-1 and Kepler-90 systems. The inclination dispersions of these systems are quantified, and it is shown that their remarkable flatness, particularly that of the TRAPPIST-1 system, makes them outliers among the known planetary systems. Motivated by this, a numerical experiment is performed for each of these systems in which we use hydrodynamic simulations of differently massed disks, together with the planets, to show that the systems’ flatness places upper bounds on the masses of their respective protoplanetary disks. Implications of this upper bound are discussed with attention to specific formation models, and some avenues for the formation of these systems are ruled out. In Chapter 4, I present a more general discussion of angular momentum deficit (AMD). In particular, I show that breaking it up into components depending solely on inclinations or solely on eccentricities can reveal underlying dynamics in certain contexts in which AMD is not conserved over time. As an illustrative example, N-body simulations of a Nice model scenario for the late-stage evolution of the Solar System are performed, which show how one such component of AMD can at times dominate over the other, and how this can evolve with time. Some consequences for planet formation from this analysis are qualitatively explored. The thesis concludes with an overview of the aforementioned work and a discussion of possible next steps to which this work paves the way.