Before coming to Oxford, Prof. Balbus had been Professeur des Universités in the Physics Department of the Ecole Normale Supérieure de Paris for nine years. He was educated at the Massachusetts Institute of Technology, where he took BS degrees in both mathematics and physics, and the University of California at Berkeley, where he obtained his PhD in theoretical astrophysics. He has also held academic posts at Princeton University, MIT, and the University of Virginia. Prof. Balbus's field of study is astrophysical fluid dynamics, with a particular interest in the behaviour of magnetised gases. He has made widely-recognised contributions to our understanding of accretion discs, dilute gases, and the interior of the Sun. Prof. Balbus is a Fellow of the Royal Society and a member of the US National Academy of Sciences. He shared the 2013 Shaw Prize in Astronomy with John Hawley for his work on accretion disc turbulence. He was awarded the 2020 Eddington Medal from the RAS, and the Dirac Medal and Prize from the IoP in 2021.

Black holes, Accretion, Theoretical Astrophysics

Inspirals from the innermost stable circular orbit of Kerr black holes: exact solutions and universal radial flow Physical Review Letters American Physical Society 129:16 (2022) 161101 Authors: Andrew Mummery, Steven Balbus Abstract: We present exact solutions of test particle orbits spiraling inward from the innermost stable circular orbit (ISCO) of a Kerr black hole. Our results are valid for any allowed value of the angular momentum a parameter of the Kerr metric. These solutions are of considerable physical interest. In particular, the radial four-velocity of these orbits is both remarkably simple and, with the radial coordinate scaled by its ISCO value, universal in form, otherwise completely independent of the black hole spin.