Research Interests

My work in astrophysics concerns the search for "invisible" objects in the dark halo of the Milky Way, or in the outer Solar System. I pioneered the gravitational microlensing technique to search for evidence of massive objects in the cosmic dark matter. The project that I lead (the Macho Project) has recorded the photometric histories of over 60 million stars, and has found evidence that about 20 percent of the dark matter in the Milky Way is made up of dark objects of stellar mass. We also showed that planetary mass objects do not comprise a significant fraction of this dark component. More recently I have started working on the search for small objects in the Solar System beyond Neptune. Objects smaller than 30 kilometers in diameter are too faint for direct detection, and my team is developing an indirect technique based on searching for the occultations of stars by these objects. This project will have sensitivity to objects as small as 3 kilometers in diameter. I am also developing techniques for scientific discovery in the automated analysis of massive datasets.

Membership Type


Election Year


Primary Section

Section 12: Astronomy

Secondary Section

Section 13: Physics