WIPAC professor Stefan Westerhoff dies at 50

WIPAC group photo in front of capitol building in Madison, WI
Stefan among WIPAC colleagues in 2016.

Stefan Westerhoff, a professor in the physics department at the University of Wisconsin–Madison, passed away on Sunday, August 5, 2018, after a long illness. He was 50.

Stefan was a leading physicist in the fields of cosmic ray physics and gamma ray astronomy and a faculty member at the Wisconsin IceCube Particle Astrophysics Center (WIPAC). He contributed to a suite of historic experiments concentrating on the search for the enigmatic sources of cosmic rays: the High-Energy-Gamma-Ray Astronomy (HEGRA) detector array in La Palma, Spain, the High Resolution Fly’s Eye (HiRes) detector in Utah, the Pierre Auger Observatory in Argentina, the Milagro telescope in New Mexico, and, in the past decade, the IceCube Neutrino Observatory, located at the South Pole and operated by UW–Madison, and the High Altitude Water Cherenkov (HAWC) Observatory near Puebla, Mexico.

Stefan started his career in particle physics, but he had the vision, many years ago, to move into particle astrophysics. At that time, few astronomers or physicists paid much attention to this struggling discipline, and he was one of the pioneers in the early and rapid expansion of this field in Germany.

Born on December 25, 1967, in Hagen (Germany), Stefan was a PhD student at the University of Wuppertal, where he graduated in 1996. He came to the US as a postdoctoral researcher at the University of California, Santa Cruz, which included a stint at Los Alamos National Laboratory in New Mexico. Following this, he was a faculty member at Columbia University from 2000 until 2007. He joined the faculty at UW–Madison in 2007, where he became a full professor in 2012.

Throughout his career, he was selected to serve on the main advisory committees covering particle physics as well as particle astrophysics, from the Subatomic Physics Evaluation Section (SAPES) of the Natural Sciences and Engineering Research Council (NSERC) of Canada, which he chaired in 2015, to the CERN Proton Synchrotron Committee and the advisory board of the Gran Sasso underground laboratory. He was elected a Fellow of the American Physical Society in 2013 and received a UW–Madison Vilas Associates Award in 2014.

Stefan’s team at IceCube performed the first measurement of the cosmic ray anisotropy in the Southern Hemisphere.

Stefan also excelled as a teacher. During his time in Madison, he taught courses ranging from core physics requirements to acoustics for musicians. As a physics teacher, Stefan was brilliant and fair, challenging and clear, and he was consistently rated as easily the best physics professor you could ever have, to quote several of his students—many of whom would organize their schedules to take as many courses with him as they possibly could.

At UW–Madison, he was a respected and admired colleague, and especially recognized for the constructive and thoughtful input given to every task he undertook, including advising undergraduate students and serving on committees for new faculty searches and overseeing tenure appointments.

Stefan’s colleagues and friends are deeply saddened by his passing and will remember him for his sharp mind, a witty sense of humor, his comforting voice and presence, and an amiable, generous, and straightforward personality. His legacy as a mentor leaves behind a cohort of scientists, not only in the IceCube and HAWC collaborations but also in other astronomy and astrophysics communities he was once a member of.

Stefan’s passion for music was well known. He preferred the classics and, among them, the opera: Beethoven, Brahms, Mendelssohn, Wagner, and many others. Stefan also was an accomplished piano player, although most of his friends never heard him play—not even when they were visiting in a room dominated by a baby grand piano—perhaps from Stefan’s inclination to always devote his full attention to his friends.

When not talking about physics or music, he would also make references to movies. As with music, he was fond of the classics, mostly films released before 1940. Yet he sometimes surprised his friends with his knowledge of sitcoms, such as The Golden Girls or Seinfeld.

Stefan is survived by his parents, Christa and Bernd Westerhoff, who visited him a few times per year but found themselves very far from Madison when Stefan’s health suddenly declined. His family and friends want to express their gratitude to Michaela Schultheis, his doctor Alissa Weber and the SSM oncology team, and the many caring nurses and social workers at Agrace Hospice & Palliative Care.

A memorial service will be held on August 25 in Madison—details will be posted here once finalized. Memorial donations can be made to Agrace Hospice & Palliative Care and/or to the Stefan Westerhoff fund at IceCube for a memorial exhibit on acoustics to be placed in Chamberlin Hall, home of UW–Madison’s Department of Physics. To donate to this fund, please use this link and write “IceCube Project” as “Fund name” and in the gift options section mention that you are making this gift in memory of Stefan Westerhoff.

(German version here.)