Planet Formation and Collisional Evolution

Planet formation is common, with a Jupiter-mass planet in close orbit around at least 5% of all main sequence stars. The systems that are observed are surprisingly diverse and very different from our solar system. Observations cannot trace the full history of planet formation, but do provide snapshots of either early protoplanetary disks, or the late stages after planetary systems or debris disks have formed. As a result, we cannot observationally connect the early and late stages of planet formation, and it is not known how such a diversity of extrasolar systems arises, or what determines the type of solar system that develops. One solution is to build a numerical model that can evolve a broad range of protoplanetary disks through to final planetary systems or debris disks. Such a complete model of planet formation has eluded the astrophysics community because of numerical limitations and incomplete/unknown physics.

We are currently developing a state of the art numerical method that will include the most realistic model of planetestimal evolution to date. The goal is to develop a complete account of planet formation. This technique will be highly efficient, and able to evolve newly formed planetesimals all the way through to planets. The results will seamlessly connect the final two stages of planet formation and capture feedback processes in which evolving protoplanets can replenish the reservoir of planetesimals. During the course of this work answers to many questions surrounding planet formation will emerge, e.g., a realistic collision evolution model for planetesimals will allow accurate growth timescales to be calculated, which will in turn determine whether giant planet cores can plausibly form from the gradual growth of planetesimals or if some faster mechanism is required. In addition, this work will predict the amount of debris produced by planetesimals during planet formation, which will be vital to interpret observations of protoplanetary disks. This work will also be useful in interpreting our own solar system. Here is a movie of a numerical simulation of an impact between two 'planetesimals'. The result is very similar to dwarf planet Haumea and the dynamical family associated with it.

Simulation of an impact between two rocky bodies

Results from a computational experiment of an impact between two rocky bodies (see fig.1). These new results are being incorporated into the computer model of planet formation providing a more detailed and accurate description of how planetary embryos grow.

Working in this area

Dr Zoe Leinhardt

Dr Philip Carter
(fig.1) Simulation of an impact between two rocky bodies
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