Nobel Prize in Physics for the man who turned Antarctic ice into a telescope

The 2026 Nobel Prize in Physics has been awarded to Francis Halzen, the physicist who led the building of a giant particle detector buried in the ice at the South Pole.

The Royal Swedish Academy of Sciences gave the prize to Professor Halzen "for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin".

Professor Halzen, 82, was born in Belgium and is a professor at the University of Wisconsin-Madison in the United States. He is the principal investigator of IceCube, which is run by an international collaboration of scientists led by the Wisconsin IceCube Particle Astrophysics Center.

"A new kind of astronomy"

Mark Pearce, chair of the Nobel Committee for Physics, said: "Francis Halzen has led an international team of researchers and engineers who have provided us with a fantastic instrument. His tenacity and scientific vision has paved the way for a new kind of astronomy."

Professor Halzen said: "It was a great surprise and I obviously didn't expect it." He added that he was working on a proposal for the future of the observatory, and hoped that winning the prize would help.

Ghost particles

Neutrinos are tiny subatomic particles with almost no mass and no electric charge. Trillions of them pass through every person every second without leaving a trace, which is why they are often called ghost particles. Because they so rarely interact with anything, they can travel across the universe in straight lines from the most violent places in space, carrying information that light cannot.

That same property makes them extremely hard to catch. To see even a handful, scientists need a detector of enormous size.

A cubic kilometre of ice

Professor Halzen began working on the idea of using the Antarctic ice to catch neutrinos in the 1980s. IceCube, completed in 2010, uses a cubic kilometre of ice deep beneath the South Pole. Thousands of light sensors hang on cables in holes drilled up to around 2.5 kilometres down. On the rare occasions when a neutrino collides with the ice, it produces a faint flash of blue light, which the sensors record.

What IceCube found

• In 2013, IceCube announced the first detection of high-energy neutrinos from outside the solar system.
• In 2017, it detected a high-energy neutrino traced to a supermassive black hole at the centre of a distant galaxy, in the direction of the constellation of Orion.
• In 2022, it provided the first evidence of high-energy neutrinos coming from an active galaxy 47 million light-years away.
• In 2023, it found neutrinos coming from our own galaxy, the Milky Way.

Those discoveries opened an era in which astronomers can study distant events using light, neutrinos and gravitational waves together.

The prize

The prize is worth 12 million Swedish kronor and will be presented in Stockholm on 10 December, the anniversary of Alfred Nobel's death.

It is the second of this year's Nobel Prizes. On Monday, the prize for physiology or medicine went to Karl Deisseroth, Peter Hegemann and Georg Nagel for optogenetics. The chemistry prize will be announced on Wednesday.