Francis Halzen, who hunts neutrinos in Antarctic ice, wins the 2026 Nobel in physics

Halzen was in Italy when the phone call came on October 6, and he told reporters afterward that the prize was “a great surprise” he “obviously didn’t expect.” The 82-year-old Belgian-born physicist, a professor at the University of Wisconsin-Madison since 1972, is the sole winner of the 2026 Nobel Prize in Physics, announced that morning by the Royal Swedish Academy of Sciences. The award is worth 12 million Swedish kronor, about $1.2 million, and it recognizes a project that most of his field once considered unworkable: turning a block of Antarctic ice into a telescope.

The Academy’s citation for IceCube

The Royal Swedish Academy honored Halzen “for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.” The prize went to him alone, and the committee’s phrasing names two things: the instrument and the discovery it made possible, both of which trace to his 1988 proposal.

The American Institute of Physics reproduced that wording in its congratulation and added that construction finished in 2010 and that the observatory began full operations in 2011.

The University of Wisconsin-Madison’s own announcement paraphrases the honor more broadly, crediting his contributions to understanding the astrophysical particles known as neutrinos, produced by the universe’s most energetic events. It counts Halzen as the sixth Nobel laureate connected to the campus and the 23rd tied to the university overall.

A cubic kilometer of South Pole ice

Neutrinos pass through planets, stars and people almost without touching anything, which makes them nearly impossible to catch and, for the same reason, a clean messenger from distant violent events. Halzen’s bet was that the ice beneath the South Pole station could do the catching. IceCube instruments a cubic kilometer of clear Antarctic ice with 86 strings of sensors at depths between 1,450 and 2,450 meters, and it picks up the faint blue light that appears when a neutrino occasionally collides with an atom in the ice.

Wisconsin’s release describes the facility as a cubic kilometer of Antarctic ice carrying thousands of light sensors, operated by an international collaboration led by the Wisconsin IceCube Particle Astrophysics Center and funded by the National Science Foundation. Nature’s report on the prize puts the sensor count at 5,160 and the construction cost at $271 million, and says the detector began to deliver within two years of completion.

The first big result arrived in 2013, when IceCube announced high-energy neutrinos from outside the solar system. Wisconsin’s timeline then lists a 2017 detection of a high-energy neutrino traced toward a supermassive black hole, and later detections from active galaxies and from the Milky Way.

The 2013 announcement rested on 28 events recorded between May 2010 and May 2012, which the university’s release at the time quoted Halzen calling it the first indication of very high-energy neutrinos coming from outside the solar system. The results appeared in the journal Science on November 22, 2013, and the collaboration’s spokesperson then was Olga Botner of Uppsala University. Halzen called the moment “the dawn of a new age of astronomy.”

Olsson’s remarks and Halzen’s reply

Eva Olsson of the Nobel committee said Halzen “realized that the ice at the South Pole could visualize these neutrino messengers” from space, opening what she called “the door to distant galaxies,” according to PBS NewsHour’s coverage of the announcement.

Halzen pointed first to the people around him. In Nature’s account he said the honor reflects on “the really courageous people” who joined his effort, on a project most conservative physicists initially rejected. At Wisconsin he called the prize “a celebration of a very unusual project” and said it was difficult to imagine pulling it off anywhere but at UW-Madison. Interim Chancellor Eric Wilcots called IceCube “like no other telescope in the world.”

A career built around one detector

Halzen holds the Gregory Breit and Vilas research professorships in the UW-Madison physics department, where he has been on the faculty since 1972. He took his master’s and doctoral degrees at KU Leuven in Belgium, co-wrote the textbook Quarks and Leptons and has more than 1,000 publications to his name. The 1988 proposal date AIP gives and the 2011 start of full operations bracket more than two decades of work on a single instrument.

Earlier honors include the 2015 Balzan Prize, the 2021 Bruno Rossi Prize and the 2026 American Physical Society Medal for Exceptional Achievement in Research. The Nobel is, per PBS, the 11th awarded to a Belgian national, a count Belgian Prime Minister Bart De Wever gave. AIP chief executive Michael Moloney said Halzen had the “audacious idea” of turning an enormous volume of naturally occurring Antarctic ice into a telescope, then led the decades-long effort to build it.

In the PBS interview Halzen said the call felt “strange,” and he added that he hopes the prize will help secure approval for a proposal he is developing.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.