My research concentrates on star clusters as tracers of the stellar populations within their parent galaxies. In most galaxies beyond the Local Group, individual stars are too faint to be resolved and studied in detail. Star clusters, on the other hand, can be detected out to large distances, and their ages and metallicities can be measured. We currently know very little about the detailed chemical evolution of stellar populations outside the Local Group, a situation I am working hard to improve by means of high quality spectroscopy of massive clusters in a variety of external galaxies.
I am also interested in the problem of multiple stellar populations in globular clusters. From spectroscopic and photometric observations, it is known that a large fraction of the stars within globular clusters have abundances of the light elements in combinations that are seen nowhere else. Why that is so remains a mystery, and while several scenarios have been proposed, none provides a satisfactory explanation. My work is mainly concerned with providing constraints on the various theories, in particular using observations of globular clusters in dwarf galaxies.
I am involved in several collaborations related to star clusters, here are a few:
As of June 2012, all activities (including teaching and research) of the Astronomical Institute (SIU) of Utrecht University have ended. I maintain a page with links to information about the closure of the SIU.
You can't connect the dots looking forward; you can only connect them looking backwards. So you have to trust that the dots will somehow connect in your future.--Steve Jobs