Bachelor, Harvard University, 1971; AM, Harvard University, 1973; Doctor of Philosophy, Harvard University, 1975.
Assistant professor, University of Minnesota, Minneapolis, 1975-1978; research associate, Harvard College Observatory, Cambridge, Massachusetts, 1978-1983; associate professor, U. Arizona, Tucson, 1983-1989; professor, U. Arizona, Tucson, 1989-1995; professor, Chalmers U. Technology, Gothenburg, Sweden, since 1996.
Member American Astronomical Society, Royal Astronomical Society (England), International Astronomical Union, Royal Swedish Academy of Sciences (foreign), American Geophysical Union.
Married Cathy Horellou, July 21, 1995. Children: Steven John, Gwenaelle Anne.