I work on the large-scale structure of the Universe and the properties of the massive objects contained within it, using both observation and theory. I am particularly known for making the first detections of the change in brightness of the microwave background radiation caused by inverse-Compton scattering in clusters of galaxies (the Sunyaev-Zel'dovich effect), and in demonstrating how this effect can be used to measure cosmological parameters.

I worked on NASA's Chandra satellite before launch, and use it and other space-based and ground-based telescopes from X-ray to optical to radio bands to study galaxies, especially those hosting massive black holes and showing signs of unusual activity.

In these areas I give professional and public presentations, but I also speak and write on more general astronomical and cosmological topics.