University of Oxford
Physics and Astronomy

Investigating the dynamics at the heart of the Milky Way

At the centre of the Milky Way lies Sagittarius A*, a supermassive black hole surrounded by an exceptionally dense cluster of stars. Because the black hole is more massive than all the surrounding stars combined, its gravity dominates the system, causing stars to follow elliptical orbits, much like Earth around the Sun. Over time, these orbits gradually change orientation through gravitational interactions, a process called resonant relaxation. The resulting orbital paths can be represented as rings, known as annuli, which interact with one another. Within this crowded region, young stars form a disc, but their origin and survival remain difficult to explain.

Barry’s project will investigate how this stellar disc evolves under the combined gravitational influence of the surrounding stars. He will combine theoretical analyses with computer simulations, accounting for the complex influence of the surrounding star cluster. The research will test whether the observed configuration of the stars can arise naturally, or whether additional massive objects, such as intermediate-mass black holes, are needed to explain it.

The findings could help explain the formation and evolution of the structures observed at the Galactic centre and place new constraints on the possible presence of intermediate-mass black holes in this region. More broadly, the project would advance understanding of how collective gravitational interactions shape dense stellar systems, and will explore the properties of many-body, strongly-interacting systems with long-range forces.