In addition to his professional legacy, colleagues remembered Dr. Gaisser as kind and unassuming, generous in sharing his expertise and his time and in his enthusiastic support for young scientists. During his work at the South Pole, where he would spend weeks at a time, he especially enjoyed the camaraderie of everyone working on the project, his wife, Julia, said, calling it a high point of his personal and professional life.
“Tom was a great scientist, great member of the Department of Physics and Astronomy and Bartol Research Institute, and a consummate gentleman,” said Edmund Nowak, professor and chair of the department, where the Bartol institute is housed at UD. “He will be sorely missed.”
Dr. Gaisser earned his doctoral degree from Brown University in 1967 and held postdoctoral positions at Massachusetts Institute of Technology and Cambridge University. He joined the Bartol Research Foundation, now the Bartol Research Institute, which was then on the campus of Swarthmore College, in 1970. When Bartol moved to UD, Dr. Gaisser continued his work as a member of the research center faculty and in 2001 was named the University’s Martin A. Pomerantz Chaired Professor of Physics and Astronomy. He retired in 2019 and was awarded emeritus status.
His broad scientific focus allowed him to play a crucial and central role in the birth and development of the new field of astroparticle physics, which has emerged at the intersection of particle physics, astrophysics and cosmology. This field studies the emissions of photons, neutrinos and cosmic rays generated by astrophysical sources like supernova explosions, pulsars, black holes and others.
“During the years I served as director of Bartol, I became ever more aware of Tom’s stature in the fields of cosmic rays and particle astrophysics,” said Stuart Pittel, professor emeritus of physics and astronomy at UD, who has known Dr. Gaisser since the two were junior researchers at Bartol. Pittel recalled having dinner a few years ago with Saul Perlmutter, a Nobel laureate in physics, and mentioning that he had been the director of Bartol. “Ah,” Perlmutter said, “Tom Gaisser.”
Dr. Gaisser was “a pivotal researcher in the field of cosmic-ray physics” since the late 1970s, making “phenomenal” contributions, the IceCube consortium said in a tribute to him. “But the reason he is known to every scientist in the field, as well as to many others in physics, is his book Cosmic Rays and Particle Physics.”
That 1990 textbook has become standard reading for young researchers in the field and has been translated into Japanese and Mandarin. Dr. Gaisser, working with Ralph Engel and Elisa Resconi, published a second, updated and expanded, edition in 2016.