Francis Halzen wins Physics Nobel for'ghost particle' hunt

Stockholm: The Belgian-American Francis Halzen won the 2026 Nobel Prize in Physics for his work creating an observatory to detect high-energy neutrinos - some of the universe's most elusive subatomic particles - and try to establish how they are made.

Halzen, 82, realised that pristine ice at the South Pole could be used to track such neutrinos, sometimes known as "ghost particles" for the way they pass through the Earth and our bodies without a trace, only interacting with matter extremely rarely. "The messengers bring information from the cosmos," Eva Olsson, of the Royal Swedish Academy of Sciences, told a press conference.

"They open the door to distant galaxies and tell us about the processes of exploding stars."

The interactions registered by the IceCube observatory in Antarctica provide information about how high-energy neutrinos are created and may even reveal previously unknown phenomena, the Academy said.

In 2014, the US-based Smithsonian magazine dubbed Halzen "Neutrino Man" when giving him one of its Ingenuity Awards, acclaiming him for an "amazing experiment (that) heralds the beginning of a new era in astronomy". It even published a comic illustrating his life: "How One Physicist’s Pursuit ⁠of the Cosmos Took Off in Antarctica".

The particle detector comprises more than 5,000 sensors set in a cubic kilometre of Antarctic ice, which extends to a depth of 2,500 metres below the surface near the Amundsen-Scott South Pole Station.

The observatory awaits blips from the nearly massless high-energy neutrinos, which unlike other particles do not lose energy or change direction, in the hope of tracing their paths back to exploding stars, gamma-ray bursts, and cataclysmic phenomena involving black holes and neutron stars. It can expect to register about one per day.

Halzen, a professor at the University of Wisconsin–Madison in the United States, first presented his idea for capturing neutrino traces at the South Pole in 1988, but the project was not completed until 2011.

"I have to emphasise how lucky I was because, when we started this project, everybody realised this was maybe a good idea, but very few thought it would work, including myself," Halzen told the press conference by telephone.

Neutrinos are electrically neutral, undisturbed by any magnetic field, which means that, in contrast to electromagnetic waves such as visible light, the direction from which they arrive points directly back to their source.

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