The 2026 Nobel Prize in Physics has been awarded to Francis Halzen of the University of Wisconsin–Madison for investigations of fundamental particles.
Ellen Moons, secretary general of the Royal Swedish Academy of Sciences, announced that Halzen, who led the development of the giant particle detector located at the South Pole, is being honored “for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.” Halzen is the first solo recipient of the physics Nobel since 1992.
“IceCube is definitely the experiment that has opened a new window to the universe,” says Karsten Heeger, an experimental neutrino physicist at Yale University. “Halzen has been a visionary in the field.”
Neutrinos are among the 17 fundamental particles in the standard model of particle physics. Electrons, photons, and quarks, the particles inside protons and neutrons, are also constituents of this roster of particles that make up all matter and light. But unlike electrons and photons, neutrinos rarely interact with matter, instead passing through objects unnoticed.
“More than 1 billion neutrinos are passing through my hand every second,” said Mark Pearce, chair of the Nobel Committee for Physics, holding up his hand at the prize announcement in Stockholm. Most of those neutrinos come from the sun.
These ghostly particles are produced by nuclear reactions, particle collisions, and other high-energy events on Earth and in space. The sun and other stars produce billions every second. Black holes, supernovas, and other cosmic entities also produce neutrinos of energies far higher than those produced by the sun.
Because neutrinos are electrically neutral and interact rarely with matter, they make great astronomical messengers, Pearce explained. If detected on Earth, they could point back to the source of these high-energy events and help us better understand the universe.
But unlike other types of neutrinos, high-energy astrophysical neutrinos are rare on Earth. This rarity, combined with the particles’ weak interactions with matter, makes them extremely difficult to detect. In the 1980s, Halzen realized that Antarctic ice could provide the enormous detection volume needed to find the elusive particles.
The resulting IceCube Neutrino Observatory, completed in 2011, consists of light sensors buried about 2 km deep in roughly a cubic kilometer of South Pole ice, making the detector literally a giant ice cube. The site’s collaborators currently include 450 researchers from 14 countries.
The entire process from the idea to the realization took more than 20 years, Heeger says. “And so, seeing a project like this, that [Halzen] conceived, coming to fruition, starting small and then building up, was an incredible engineering feat of international collaboration.”
The observatory’s sensors do not see neutrinos directly. When a neutrino interacts with an atomic nucleus in the ice, it can produce a charged particle that travels through the ice and gives off a flash of blue light. By tracking the path and direction of the light, astronomers can estimate where the original neutrino came from. A cubic kilometer of ice has a mass of about 1 billion metric tons, so even a rare interaction with matter happens frequently enough to be detected.
Within 2 years after IceCube became fully operational, researchers found evidence of high-energy neutrinos from beyond Earth. “IceCube now paves the way for a new type of astronomy,” Pearce said.
Asked whether this year’s prize announcement is surprising, Michael Moloney, CEO of the American Institute of Physics, says no.
“It’s not a surprise in the sense that humanity has always been staring up at the cosmos, from our earliest days, trying to understand what’s going on. So when there’s an extraordinary shift in our capability as a species to probe and examine the nature of the universe, it’s always inspiring.”
Sydney Smith and Ana Georgescu contributed to this story.
UPDATE:
This story was updated on Oct. 6, 2026, to add more information about the work behind the prize, including quotes from Karsten Heeger and Michael Moloney.
CORRECTION:
This story was updated on Oct. 9, 2026, to correct the depth of the sensors in the South Pole apparatus. They are buried at a depth of 2 km, not 3.2 km. And the description of cosmic entities producing high-energy neutrinos was corrected. Black holes and supernovas produce these, not black holes in supernovas.
Ana Georgescu covers a wide range of topics in physical sciences and is also a frequent contributor to the business desk.
