Exploring The Architectures Of Planetary Systems That Form In Thermally Evolving Viscous Disc Models

Abstract

The diversity in observed planets and planetary systems has raised the question of whether they can be explained by a single model of planet formation or whether multiple models are required. The work presented in this thesis aims to examine the oligarchic growth scenario, to determine whether the core accretion model, where planets form bottom-up, can recreate the observed diversity. I begin by exploring how changing model parameters such as disc mass and metallicity influence the types of planetary systems that emerge. I show that rapid inward migration leads to very few planets with masses mp > 10M⊕ surviving, with surviving planetary systems typically containing numerous low-mass planets. I examine what conditions are required for giant planets to form and survive migration, finding that for a planet similar to Jupiter to form and survive, it must form at an orbital radius rp > 10 au. In the second project in this thesis, I update the physical models before examining whether a broader range of parameters can produce planetary systems similar to those observed. I find that compact systems of low-mass planets form in simulations if there is sufficient solid material in the disc or if planetesimals are small, thus having increased mobility. I also find that giant planets can form when the solid abundance and mobility of planetesimals are high, however they all undergo largescale migration into the magnetospheric cavity located close to the star. For the final project of this thesis, I examined the effects that disc radial structuring has on the formation of giant planets. I find that by including radial structures, numerous giant planets are able to form at large orbital radii and survive migration. The observed period valley between 10–100 days is also recreated, of which I attribute to disc dispersal late in the disc’s lifetime.