The formation of planetary systems: physics, populations, and architectures

Abstract

We review the progresses made in global theoretical models of planetary system formation in the last decade using the example of the planetary system formation framework known as the Bern Model that has been continuously developed since before the beginning of the NCCR PlanetS. We highlight major developments and applications that have since been implemented, reflecting important recent advancements of planet formation theory overall, such as MHD wind-driven disk evolution, planetesimal evolution including fragmentation, dust evolution and pebble accretion, formation of planets in structured disks, interior structure models allowing for compositional gradients, as well as the analysis of the emerging planetary system architectures and the identification of different classes of architectures. We discuss how these new models impact the formation and evolution process and translate into different populations of planets and planetary systems. We also discuss the major strengths of the Bern Model, including successful predictions of the break in the planetary mass function at 30 MEarth, the prevalence of low-mass planets, the radius pile-up around 1 RJupiter, and the evaporation valley, with the recent New Generation Planetary Population Synthesis models with 100 seeds per disk providing quantitive matches to many RV-survey and Kepler diagnostics. This includes key characteristics of planetary system architectures. We also highlight the limitations of this model, some of them were addressed during the course of the NCCR PlanetS: the inclusion of the early phases of planet formation from dust to planetesimals, the hybrid pebble-planetesimals accretion of solids, simplified interior structure models, reliance on simplified parametrizations that may not encapsulate the full complexity of physical processes, and computational constraints.