Planet Formation Group
Astrophysics Department, School of Physics, University of Bristol


The group focuses on the formation and evolution of planets and small bodies, such as asteroids and comets through the use of numerical simulations. Our work involves numerical simulations of planet formation, covering the topics of collision evolution of planetesimals, young planets in transitional disks, circumbinary planets, compositional evolution of protoplanets and the moon formation puzzle.

Planetesimal Collisional Evolution and Planet Formation

The evolution of planetesimals, the building blocks of planets, is dominated by collisions with other planetesimals. The outcome of these collisions depends on impact angle, spin, target to projectile mass ratio, and impact speed.

Young planets in transitional disks

Transitional disks are characterised by a flux deficit in the near-infrared wavelengths with respect to a classical protoplanetary disk, but otherwise have similar spectral energy distributions. The accepted explanation is a lack of optically thick material in the inner disk, implying a hole or large gap.

Circumbinary planet formation

There is great difficulty in explaining the presence of circumbinary planets (planets that orbit two stars - think Star Wars’ Tatooine and Doctor Who’s Gallifrey…!), recently observed by the well known exoplanet hunting Kepler mission.

Composition of the Earth

Our own solar system is an important benchmark for theories of planet formation. The assumption that the Earth has a chondritic composition in terms of its refractory lithophile elements has recently come under question as several indications of a non-chondritic composition have been found. We are running simulations to investigate the idea that the Earth's non-chondritic composition could be the result of collisional erosion of differentiated planetesimals during its formation.

Moon formation

The current most widely-accepted scenario for Moon formation is a large impact between the proto-Earth and another smaller planet. This impact theory must be able to explain any compositional differences/similarities between the Earth and Moon; there are various flavours of the impact theory that attempt to do this (canonical, fast-spinning Earth, two sub-Earths), each of which tells a different story about the chemical composition/state of the disk. After the impact a debris disk comprised of material thrown out from both objects forms around the Earth.