I grew up in the Twin Cities, Minnesota, and did my undergrad in physics and astronomy at the University of Minnesota. My hobbies have variously included hiking, biking, ultimate frisbee, lindy hop, and keeping tropical freshwater fish in my office. I am of the strong opinion that extreme cold such as that found in Minnesota and Canadian winters feels better than the mild-yet-humid cold of marginally-warmer climates, and that having strong seasonal climate variations builds character.
Professor, Acting Director of CITAn-body and hydro simulations, origin of galaxy spin, dark energy: 21cm cosmology, BAO, absorber acceleration. FRB and pulsars: gravitational waves, wave optics, lensing.Ph.D. 1995, Princeton
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.