In addition to one or more stars, a solar system can contain a wealth of other material in the form of planets, moons and debris. These smaller bodies perturb one another via mutual gravitational interactions. Such objects can undergo close encounters, resonances and long-term secular interactions, and smaller bodies may experience further perturbations from radiation forces. The presence of a gas disc at early times introduces additional dynamics into the system. Such effects can lead to orbital evolution, and may even cause objects to collide or be ejected.

The IoA conducts a significant amount of research into the dynamics of planetary systems, covering multiple stages in the stellar lifetime. This includes modelling interactions between newly formed planets and protoplanetary or transition discs at early times, and examining the dynamics of planet-planet and planet-debris interactions later on in the star’s life. We also consider the evolution of planetary systems that undergo encounters with other stars. Finally we examine late stage system evolution, modelling planetary systems around white dwarf stars.

The image below shows the evolution of a planet that is scattered out into a disk of small bodies analogous to our Kuiper belt (a debris disk). Interaction between the planet and the small bodies circularises the planet orbit and imparts new radial structure on the disk.