Protoplanetary discs and planet formation

Planets form in cold discs of dust and gas around young stars like the sun. We know, however, that only a small fraction of material in these discs ends up in planets; most of the disc is either accreted on to the star or blown away in winds or jets. Much of my research looks at the evolution of these protoplanetary discs, and the influence they exert on forming planetary systems. The figure to the right, from my PhD thesis, shows a numerical simulation of disc clearing by photoevaporation.

More recently, I have begun to look in detail at how the interaction between planets and their parent discs shapes the formation of planetary systems. I have built detailed numerical models of how these systems evolve, and used high-performance computing facilities to run large numbers of models in order to make statistical predictions for the properties of both protoplanetary discs and exoplanets. With PhD student Alex Dunhill, I looked into how disc-planet interactions alter planetary orbits, particularly the planets' eccentricity. With PhD student Tom Hands, I am studying the formation and dynamics of multi-planet systems. Recently I have also begun to model the evolution of discs around binary stars, with the aim of understanding the formation and evolution of circumbinary planets such as Kepler-16b.

Super-massive black holes

My other main topic of research is the formation and evolution of super-massive black holes (SMBHs) at the centres of galaxies. These cosmic giants are millions to billions of times more massive than the sun, and play a key role in shaping the formation and evolution of galaxies.

A key question in the evolution of SMBHs is how they accrete gas. Much of my research in this area has focused on Sgr A*, the SMBH at the centre of the Milky Way. I showed how the gas disc around Sgr A* broke up into stars (shown in the simulation to the left), and looked in detail at how those stars grew and interacted. I've also looked at how gas discs drive pairs of SMBHs together, following the merger of two massive galaxies. Recently, with SURE summer student Sarah Smedley, I investigated at the fate of the gas left over when the disc around Sgr A* formed stars.

To read more about specific projects, please go to my publications page.