Francis Halzen wins 2026 Nobel Prize in Physics for IceCube neutrino discovery

Francis Halzen has been awarded the 2026 Nobel Prize in Physics for his pioneering role in conceiving and leading the IceCube Neutrino Observatory. The Belgian particle physicist from the University of Wisconsin-Madison was honored for decisive contributions that led to the discovery of high-energy neutrinos of astrophysical origin. The Royal Swedish Academy of Sciences announced the award on 6 October 2026.

Mark Pearce, chair of the Nobel Committee for Physics, praised Halzen for leading an international team and providing a fantastic instrument for a new kind of astronomy. Halzen, born in Tienen, Belgium in 1944, said winning the prize was a great surprise. He addressed the press conference by phone.

From bold idea to Antarctic detector

Francis Halzen first presented his vision for capturing neutrinos at the South Pole in 1988. He proposed converting a chunk of the glacial ice into a neutrino observatory. This bold idea led to the creation of the IceCube Neutrino Observatory, where Halzen serves as principal investigator.

To build IceCube, an international collaboration of more than 450 people from 58 institutions across 14 countries embedded thousands of basketball-sized light detectors into a cubic kilometre of ice. The sensors were placed in deep holes drilled with hot water, a mile beneath the Antarctic surface. The observatory was completed in 2010 and began full operations in 2011.

How IceCube detects the invisible

Neutrinos are electrically neutral subatomic particles that permeate the universe. More than a billion pass through a human hand every second, mostly from the sun. They rarely interact with matter. Halzen’s work focuses on rare, high-energy neutrinos from deep within the cosmos.

IceCube detects these ghostly particles when they very rarely interact with an atomic nucleus in the ice. This interaction produces Cherenkov radiation, a flash of blue light. The network of thousands of sensors buried two kilometres down captures this light. The pristine, stable South Pole ice provides an ideal environment free from interference. The sensor data allows researchers to trace a neutrino’s trajectory back to its cosmic origin.

Discovery and legacy of cosmic neutrinos

IceCube detected the first high-energy neutrinos from beyond the solar system just a couple of years after becoming operational. This fulfilled Halzen’s vision. In 2017, it identified the first definitive source of a single high-energy cosmic neutrino: a blazar called TXS 0506+056. In 2023, IceCube identified neutrinos originating from within our own Milky Way galaxy.

Mark Pearce described neutrinos as "ghost-like messengers from the cosmos" at the press conference. Halzen reflected on the project's challenges. "When I reflect on this moment, I have to emphasise how lucky I was," said Halzen. He admitted few initially believed the project would work, including himself.

He hopes the Nobel Prize will reflect on the early collaborators. It feels strange. I hope it reflects on the really courageous people who joined me in the beginning of this project when no really respectable, conservative physicist would have joined me, but many talented people did. IceCube continues to collect data, providing knowledge about violent cosmic settings and potentially revealing unknown phenomena. The prize amount is 12 million Swedish kronor.