My research focuses on galaxies, galaxy clusters, and the large-scale structure of the universe. Over the years I’ve studied giant cannibal galaxies, orphaned star clusters, the cosmic web, and other curios of the cosmos. As Edwin Hubble said, “We measure shadows, and we search among ghostly errors of measurement for landmarks.”
I began my career as a theoretical astrophysicist – my PhD thesis at Yale University was a computational study of how the properties of galaxy clusters might depend on the type of dark matter that dominates the universe. But over time I moved into observational astronomy.
I’ve been Principal Investigator of six successful Hubble Space Telescope programs to date and co-Investigator on many others. I’ve also used most major ground-based telescopes around the world (Keck, Subaru, VLT, Gemini, DCT, CFHT, KPNO, CTIO, etc.) in my research.
The image below shows some orphaned star clusters (in green circles) that my colleagues and I discovered with Hubble. They probably once belonged to galaxies, but a sudden gust of gravity flung them into space where they now wander freely. Each of those tiny dots is actually a system of roughly a million stars.