Physicist Wins Nobel Prize for Developing a Massive, Ice-Embedded Observatory That Detects Ghostly Cosmic Particles

Francis Halzen of the University of Wisconsin-Madison led the effort to build the IceCube Neutrino Observatory in Antarctica. His work birthed the field of neutrino astronomy

Georgia Michelman | Editorial Intern

October 6, 2026 3:51 p.m.

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On October 6, the 2026 Nobel Prize in Physics was awarded to Francis Halzen, a theoretical physicist at the University of Wisconsin-Madison, for his role in developing a massive observatory to detect ghostly cosmic particles called high-energy neutrinos.

These electrically neutral and nearly massless particles constantly whiz through space, although they seldom interact with ordinary matter, which makes up stuff we can see like planets and people. In fact, roughly 100 trillion zip through your body per second. Neutrinos with low energies are produced by everyday astrophysical phenomena, such as nuclear fusion in the sun.

But rare, high-energy neutrinos—the ones that have long fascinated the new Nobel laureate—are made by the most violent processes in the universe, including stars exploding in supernovas and black holes gorging themselves. The strange particles can be traced to the faraway astronomical objects that spewed them. And Halzen led efforts to establish an enormous, icy neutrino detector in the heart of the South Pole.

“His tenacity and scientific vision [have] paved the way for a new kind of astronomy,” says Mark Pearce, chair of the Nobel committee for physics and a physicist at the KTH Royal Institute of Technology in Sweden, in a statement.

Born in Belgium in 1944, Halzen has spent the bulk of his career in the American Midwest. But the neutrino observatory he runs—called IceCube—lives in Antarctica. That’s because in the 1980s, Halzen came up with a clever strategy to catch these elusive high-energy particles: the southernmost continent’s glacial ice.

On the rare occasion that a neutrino bumps into an atom, the interaction produces a faint flash of light. Antarctica’s ice is a prime place to spot such signals. If you dig deep enough, it’s completely dark. What’s more, there would be no interference from large animals, low levels of radioactive substances and no earthquakes.

“His bold idea—using Antarctic ice as a neutrino telescope—has paid off spectacularly,” Francesca Di Lodovico, a physicist at King’s College London, tells Nature’s Elizabeth Gibney and Davide Castelvecchi.

Halzen and colleagues finished constructing the IceCube Neutrino Observatory in 2011. Operated by UW-Madison and primarily funded by the National Science Foundation, the facility is a cubic kilometer of ice equipped with 5,160 light sensors. They’re attached to vertical strings thread through 86 boreholes and extending to depths of up to roughly 8,000 feet.

In 2013, the collaboration of scientists working on the observatory reported its first evidence of high-energy neutrinos that streamed in from beyond the solar system. “It is gratifying to finally see what we have been looking for,” Halzen said at the time in a statement. “This is the dawn of a new age of astronomy.”

This work, which birthed the field of neutrino astronomy, has since been followed by observations of ghost particles from our Milky Way galaxy and several other galaxies.

“It’s been a while since the Nobel Prize has gone to a single individual, and that points to the uniqueness of [Halzen’s] vision,” says Richard Fitzgerald, editor-in-chief of Physics Today, a magazine published by the American Institute of Physics, to CNN’s Issy Ronald and Katie Hunt. “It took a team of hundreds of people to build it, but it all started with one person.”

The observatory is still hunting for neutrinos today, and researchers have plans to expand it to eight cubic kilometers of South Pole ice. The IceCube collaboration included about 450 international scientists at roughly 60 institutions as of January 2025.

“When we started this project, everybody realized this was maybe a good idea but very few thought it would work, including myself,” Halzen said during a livestream of the award announcement. “So, this was kind of an adventure where success wasn’t guaranteed.”

The Nobel committee will continue revealing winners of its various award categories this week and early next week. Each award comes with 12 million Swedish kronor (about $1.2 million), which gets split among the laureates. Halzen, of course, gets the full amount—the first time since 1992 the Physics Nobel has gone to just one person.

Georgia Michelman is a New York-based science and health journalist and Smithsonian magazine’s current intern from the 2026 class of New York University’s Science, Health and Environmental Reporting Program. Her work has appeared in Science, Knowable Magazine, Live Science and elsewhere.