Belgian-born physicist Francis Halzen has won the 2026 Nobel Prize on Physics for his work in detecting high-energy elusive particles called neutrinos that come from deep in space. His pioneering contribution is the founding of a giant detector, the Ice-Cube Neutrino Observatory, at the South Pole. Halzen first proposed the Ice-Cube project in 1988, realising that the clear ice beneath the South Pole could act as a detector, so on the rare occurrence a neutrino strikes an atomic nucleus, it gives off a flash of light that buried sensors can record. Its results have helped to found the fields of neutrino and multi-messenger astronomy, which help physicists to unlock the mysteries of the Universe through observing highly energetic events from deep in the cosmos.
Neutrinos are the second most common particle in the Universe, after photons. Neutrinos are tiny elusive particles that are everywhere but cannot be easily detected as they rarely interact with other particles. They are passing through human bodies and other objects around without them noticing. The interactions of neutrinos with an atomic nucleus can rarely be observed when the neutrinos are of high enough energy and with the right equipment. Neutrinos have nearly no mass and carry no electric charge, so they can cross between planets, stars and human bodies without being altered, making them rare and hard to catch. There are roughly 100 trillion solar and cosmic neutrinos that pass through our bodies every second. The high energy neutrinos can be generated by mysterious natural particle accelerators in the universe which can fire up particles to energies that are up to a million times higher than can be achieved in any laboratory on Earth. Evidence are found for neutrinos coming from supermassive black holes in other galaxies, and they shine so strongly that when you look at a neutrino sky you don’t see the Milky Way.”
More than 1 billion neutrinos pass through a hand every second, but high-energy neutrinos are extremely rare and hard to detect. Ice-Cube was designed to study the particles when they fly out of some of the most energetic environments in the Universe, such as supernovae and ã-ray bursts. Because neutrinos pass straight through matter, they provide a straight line back to these events, providing researchers with a unique way of probing astrophysical phenomena. Despite being all around us, neutrinos are fiendishly difficult to detect because they are unaffected by magnetic fields and rarely ever interact. In the 1980s, Halzen had the idea to use threads of detectors, lowered more than 1.5 kilometres into holes drilled into the clear ice of the Antarctic — which is free from many types of interference — to detect the rare and faint flashes of light when a fast-moving neutrino hits an atom. As long as the volume was big enough, Halzen theorized that the set-up could catch neutrinos and the path would reveal the direction from which they come, allowing researchers to trace their origins in the cosmos.
The Ice-Cube Neutrino Observatory — an array of 5,160 sensors —was completed in 2011 at a cost of US$271 million, funded by the US National Science Foundation. In 2014, Ice-Cube discovered three neutrinos with energies that blew all others out of the water. Nicknamed Bert, Ernie and Big Bird, they had energies on the scale of peta-electronvolts, thousands of times more energetic than those produced in Earth’s most advanced particle colliders. And three years later, the collaboration made a long-awaited discovery of a high-energy neutrino that they could for the first time trace back to a specific source — a distant galaxy, called TXS 0506+056, often referred to as ‘the Texas event’. Follow-up observations suggested that the source was a ‘blazar’, a violent galaxy harbouring a supermassive black hole at its core, that can flare up in brightness. Studies from a suite of telescopes viewing the blazar using different methods described the source across seven papers in 2018.
Halzen was born in Tienen in Belgium in 1944 and studied at the country’s University of Louvain in Ottignies-Louvain-la-Neuve. He trained as a particle physicist, working at CERN, Europe’s particle-physics laboratory near Geneva, Switzerland, before moving to Wisconsin in 1971.Halzen, who is based at the University of Wisconsin–Madison, takes home all of the 12-million Swedish kronor (US$1.2-million) prize, announced by the Royal Swedish Academy of Sciences in Stockholm on 6 October. It is the first time since 1992 that the physics prize has been awarded to only one winner.
“It was a great surprise and I obviously didn’t expect it,” said Halzen, speaking to the Nobel press conference after the prize was announced. “This reflects on the really courageous people who joined me in this project when really no respectable conservative physicist would have joined me, but many talented people did and that’s why I’m here.” Halzen is “a father figure for neutrino astronomy”, says Paschal Coyle, a neutrino physicist at Aix-Marseille University in France and the spokesperson of KM3NeT, a similarly large observatory being built in the Mediterranean Sea.
Belgian physicist Francis Halzen has won the 2026 Nobel Prize in Physics for creating a giant detector in Antarctica that captures neutrinos, the so-called “ghost particles” from space that scientists believe offer clues to how the universe evolved. The Royal Swedish Academy of Sciences announced the prestigious award in Stockholm on Tuesday, crediting Halzen with a central role in building the Ice-Cube Neutrino Observatory. The neutrino interactions collected by the observatory provide information about how high-energy neutrinos are created and may even reveal previously unknown phenomena, the Academy said.
“It was a great surprise, and I obviously didn’t expect it,” Halzen said, speaking to the committee by phone from Italy, in a call broadcast at the news conference to announce the winner. The 82-year-old said it was predicted before that he would win the Nobel Prize, but the announcement still made him feel “strange”.
“The neutrino interactions that are continuously collected by Ice-Cube will provide researchers with novel knowledge about the violent settings in which high-energy neutrinos can be created — and could even reveal previously unknown cosmic phenomena. They opened the door to distant galaxies and tell us about the processes of exploding stars.”
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