Francis Halzen Wins 2026 Nobel Prize in Physics for IceCube's Discovery of Cosmic Neutrinos

The 2026 Nobel Prize in Physics has gone to a single scientist, Belgian-born Francis Halzen. The Royal Swedish Academy of Sciences honoured him for building a telescope inside the ice of Antarctica and using it to catch some of the most elusive particles in the universe. The academy announced the award in Stockholm on Tuesday. It cited Halzen's "decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin."

Halzen, 82, is a professor at the University of Wisconsin–Madison in the United States and the principal investigator of IceCube. He wins the full prize of 12 million Swedish kronor, about $1.2 million. Recent physics prizes have usually been shared among two or three people, so a sole winner is unusual.

Catching ghost particles

Neutrinos are tiny, almost massless particles that barely interact with anything. Trillions pass through every person each second without leaving a trace. That makes them very hard to detect, but it also makes them useful. Light and charged particles can be absorbed or bent on their way across the universe, while neutrinos travel in straight lines from their source. That means they can carry information from the most violent places in the cosmos.

Halzen's idea was to turn the South Pole ice sheet into a giant detector. IceCube is a cubic kilometre of deep, clear Antarctic ice fitted with thousands of light sensors lowered into holes drilled with hot water. When a neutrino occasionally collides with an atom in the ice, it produces a faint flash of blue light. The sensors record that flash, and scientists use it to work out the particle's energy and direction.

From construction to discovery

The detector was completed in 2010 after years of construction in one of the harshest places on Earth. Within a few years the collaboration reported something physicists had long sought: neutrinos with energies far beyond anything produced in the Sun or the Earth's atmosphere. They could only have come from outside our galaxy's neighbourhood. Later work linked some of these particles to specific sources, including a distant galaxy powered by a supermassive black hole. This helped establish neutrino astronomy as a new way of looking at the universe.

The discovery has also fed into multi-messenger astronomy, in which telescopes that observe light, gravitational waves and neutrinos coordinate to study the same cosmic event.

Nobel week continues

The physics prize is the second of this year's Nobel announcements. On Monday, the medicine prize went to Karl Deisseroth, Peter Hegemann and Georg Nagel for their work on optogenetics, a technique that uses light to control nerve cells. Chemistry is next, followed by literature, peace and economics later in the week and next week.

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