Giant planet formation around HR8799

Sammanfattning: In the thriving field of exoplanet research new discoveries are made all the time, and while most of the observed systems can be explained with classical planet formation models - some are much harder to explain. When stars form they are often surrounded by the remaining material of the nebulae they formed from. Some of this remaining material forms into a protoplanetary disk around the protostars due to the conservation of angular momentum and the intrinsic movement of the gas, in this protoplanetary disk planets can form. Planet formation depend strongly on the environment in which they form, so the properties and evolution of protoplanetary disks is an important part of understanding planet formation. In the case of stars that are more massive then the Sun this field is largely unexplored. In this project we look closer to one of these systems, HR8799. That, as will be shown, is not obvious how it formed and evolved. We explore the protoplanetary disk and its evolution around a young 1.47 solar mass star using a temperature structure as a function of radius and hydrodynamic simulations. This disk structure will serve as an environment for planet formation to recreate HR8799, which is an observed exoplanet system with four super jovian planets (5+ Jupiter mass) on wide orbits(14.5, 24, 38 and 68AU). To grow and evolve the modeled planets we use a N-body code in a parameterized space that represents the protoplanetary disk, in which we place planet seeds and let them grow by pebble and gas accretion while including migration, interactions with the protoplanetary disk and dynamics between the planets. Starting the simulation with four planets, we define a stable system as one where no collisions or ejections of planets occur. We find that the survival rate of systems is below 10% and there are multiple parameters that influence the survival rate. Our search focused on the viscosity parameter alpha as it greatly affects the disk structure, that in turn affects the planets growth and migration. We also varied the disk age and the pebble metallicity. We do not find an exact match for HR8799 in our survivors, but we do find stable systems with four giant planets, over three Jupiter masses on wide orbits, where the outer planet is on >50 AU orbit. In this thesis I will show that it is possible to grow and evolve stable systems with giant planets on wide orbits via pebble accretion as main core growth mechanism.