Emeritus Faculty

I study the physics in stellar atmospheres.  The physics is intriguing  because the conditions, which cannot be recreated in our labs, are changing extremely rapidly between the dense stellar interior and the near vacuum of space.  However, we have the great advantage of being able to observe directly the brightness and spectrum of the stellar atmosphere.  A recent revolutionary observational development is the technique of optical/infrared interferometry that resolves the surfaces of the nearer stars.  My approach concentrates on the bright stars that can be observed in the greatest detail, and to interpret those observations using computer models

I use variable stars to study the nature and evolution of stars. My current interest centers on

pulsating red giants and supergiants, which represent the semi-final stages of stars’ lives, and are poorly-understood, compared with other variable star types.  I use archival data, especially from the

American Association of Variable Star Observers (AAVSO), which stretches back for a century or more, edit the Journal of the AAVSO, and otherwise facilitate the contributions of skilled amateurs to

variable star research. I am also engaged in a wide variety of astronomy education and outreach projects.

My research focuses on many aspects of high-redshift galaxy clusters.  I am involved in a number of large optical/IR imaging surveys to create large samples of clusters up to redshift of 2.  These provide cluster samples for projects in galaxy and cluster evolution and observational cosmology.  These include spectroscopic surveys of cluster galaxies, the evolution and formation of clusters, the roles of environments in the evolution of galaxies, the morphology of galaxies in clusters, gravitational lensing, and the applications of galaxy clusters to cosmology.  I also work on photometric redshift

techniques, and their applications to galaxy evolution studies involving large galaxy photometric catalogues.