July 3, 2025
Remembered for groundbreaking science, thoughtful collaboration, and adventurous spirit
Priscilla Diane Chapman Frisch, University of Chicago Research Professor in Astronomy and Astrophysics and a world-leading scientist on the heliosphere and the local interstellar medium, died on April 2, 2025, at her home in Hyde Park, Chicago. She was 81.
A member of the Department of Astronomy and Astrophysics for nearly 50 years, Frisch made lasting contributions to heliosphere science, organized a large-scale international collaboration to map the interstellar magnetic field, and held prominent roles in NASA missions, including the currently orbiting Interstellar Boundary Explorer and the soon-to-be-launched Interstellar Mapping and Acceleration Probe.
“She had great physical intuition,” said Jeffrey Linsky, Research Professor Emeritus in Astrophysical & Planetary Sciences at the University of Colorado Boulder. “She could piece together many parts of an astrophysical puzzle (observations and theory) to come up with a unified picture.”
“She was an original thinker with broad interests that led her to connect disparate models and data sets, sparking collaborations and pushing the fields of local interstellar medium and heliosphere studies forward,” said John Slavin, astrophysicist at the Harvard-Smithsonian Center for Astrophysics.
A passionate and persistent path
Born in Los Angeles to Richard Courtney Chapman Jr, AB’39, and Patricia Blasdel, AB’39, Frisch was driven from childhood by a deep love of nature and a curiosity about stars and the vast dark sky. She grew up exploring, including deep-sea fishing on her father’s boat in the Pacific, stargazing from the ocean around Catalina Island.
Frisch attended the University of Colorado Boulder, where she first learned to rock climb—a passion for the high mountains and backcountry that would endure throughout her life—before transferring to UC Berkeley and graduating in 1966.
She was accepted into the astronomy graduate program at Berkeley—in part because Nobel Laureate Owen Chamberlain wrote her a recommendation letter after she was the only undergraduate student in his statistical mechanics course to solve a problem he deemed too difficult for the class.
Her first papers were published after she married Henry Frisch and moved to Chicago, where Henry had accepted a position at the University of Chicago. In 1974, the year Frisch’s first daughter, Sarah, was born, pioneering space physicist John Simpson gave Frisch her own office in the UChicago Laboratory of Space and Astronomy building in the Enrico Fermi Institute, where she worked alongside solar research luminaries Subrahmanyan Chandrasekhar and Eugene Parker. She received her PhD in Astronomy from Berkeley in 1977, the year her second daughter, Genevieve, was born.
Much of Frisch’s research focused on what is known as the ‘heliosphere.’ The sun and its planets are surrounded by a region of space dominated by the sun’s wind and magnetic field. The solar system and this protective bubble are moving through multiple ‘clouds’ consisting of charged and neutral atoms and molecules, dust grains, electromagnetic radiation, and magnetic fields. This interstellar matter, called the local interstellar medium, penetrates the solar system and can be studied by observing the selective absorption of light along the sightline to nearby stars.
As the solar system plows through the galaxy, “it creates a series of complex and amazing interaction regions, including a strong bow structure in front and a wake behind it, much like a ship moving through the sea,” explained Nathan Schwadron, Professor of Physics & Astronomy at the University of New Hampshire. Frisch sought to answer the question of where the solar system and heliosphere are within that sea.
Frisch was deeply interested in how our voyage through space, and the composition and motion of interstellar clouds near the sun, shaped the past and will affect the future of the solar system. It is a complex subject with many seemingly independent but interrelated ingredients; Frisch systematically worked through these in more than 160 publications on the components and properties of the local environment of the solar system.
In 2005–06, when interest in the field had grown, Frisch initiated and edited Solar Journey: Significance of our Galactic Environment for Heliosphere and Earth (Springer 2006), a comprehensive book on the interactions between the interstellar medium and the heliosphere.
“Frisch turned the attention of the scientific community to the changes in the solar system throughout its history due to interstellar environmental variations and their impact on the habitability of our planet and, by extension, other star systems,” said Eberhard Moebius, Professor Emeritus in the Institute for the Study of Earth, Oceans, and Space at the University of New Hampshire.
In 2005, Frisch organized an international collaboration to measure polarization of starlight in both the Northern and Southern Hemispheres to map the interstellar magnetic field.
She also contributed her expertise in the local interstellar medium and magnetic field to two NASA missions. In 2007, she began collaborating on the Interstellar Boundary Explorer mission, launched in 2008 to investigate how the heliosphere interacts with interstellar space. In 2014, she joined the Interstellar Mapping and Acceleration Probe mission, set to launch later this year to study the elemental makeup of the interstellar medium, its interaction with solar wind, and the mechanisms by which solar particles get energized.
Her colleagues remember Frisch as an independent thinker and a gracious and thoughtful collaborator, driven by a deep desire to uncover unknowns in the natural world around us.
Vikram Dwarkadas, Research Professor in Astronomy and Astrophysics at UChicago, describes the breadth of Frisch’s expertise: “Priscilla was a world-renowned expert on the local interstellar medium, its constituents, its kinematics and dynamics, the position of the sun in the local interstellar context, the Local Bubble, and the local interstellar magnetic field. In this context, she explored areas as diverse as radioisotopes in the local geologic record, the galactic cosmic ray population, star formation in the local interstellar medium, the properties of the heliosphere, and charge exchange at shocks.”
‘A clear sense of the route’
Throughout her life, Frisch enjoyed hiking, climbing in the Colorado and California mountains, and skiing in the western U.S. and the Alps. As a student, Frisch served as the president of the Berkeley Hiking Club. (The male members of the club once went on a climb without inviting the women; in response, Frisch, with her sister providing the belay, climbed out of an upper window of the 300-foot-tall Berkeley campus bell tower and tied an enormous red bow around the spire at the top.)
Frisch’s husband, Henry, noted the resemblance of high-wall technical rock-climbing to Frisch’s approach to her investigation of the complex system of the heliosphere and interstellar environment: “In both cases, one has to have an all-absorbing focus on the next move while maintaining a clear sense of the route from bottom to top.”
Frisch was also active in the folk-dance scene in Berkeley, and after relocating to the flat Midwest, exercised her athleticism through the UChicago whitewater paddling club.
She was a cofounder of the Teachers Academy for Math and Science and the Chicago Education Federation, as well as active in the Chicago School Reform movement that culminated in reform legislation passed by the Illinois Legislature in 1988.
Frisch is survived by husband Henry, daughters Sarah Tenaya and Genevieve Alexandra, and three grandchildren. The Department of Astronomy at Berkeley will establish in her name a fellowship to support students who have followed untraditional paths for love of their science.