Rudy studies the extreme physics that occur in and around neutron stars and black holes. He performs those studies by looking how those extreme objects react to the accretion of matter. His long-term goals are to understand the accretion processes involved and the behavior of matter at extreme densities as seen in neutron stars. In his research, he uses data obtained using the largest telescopes in space as well as on Earth. He teaches mostly in the BSc Physics & Astronomy program, and in particular observational courses using the Anton Pannekoek Observatory, associated with the Anton Pannekoek Institute. He is the care taker of this observatory.