By Niklas Pollard, Johan Ahlander and Simon Johnson
STOCKHOLM, Oct 6 (Reuters) - Belgian-American particle physicist Francis Halzen won the 2026 Nobel Prize in Physics for his work creating an observatory to detect some of the universe's most elusive particles - high-energy neutrinos - and trying to establish how they are made.
Halzen, 82, realised that ice at the South Pole could be used to track neutrinos, sometimes known as "ghost particles" for the way they pass through the Earth and our bodies
without a trace, and only interact 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."
HALZEN HAILED FOR DETECTING 'MESSENGERS FROM THE COSMOS'
The neutrino interactions collected 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 is set in a cubic kilometre of pristine Antarctic ice, which extends to a depth of 2,500 metres below the surface, near the Amundsen-Scott South Pole Station.
The observatory searches for the nearly massless high-energy neutrinos 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 first presented his idea for capturing neutrinos, which unlike other particles do not lose energy or change direction, at the South Pole in 1988, winning over others to a project that was eventually completed in 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 even the strongest 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.
The icebound observatory has been able to determine that high-energy neutrinos originate within but also far outside our own galaxy, setting in motion an interstellar quest to find the objects and processes that create them.
Halzen, a professor at the University of Wisconsin–Madison in the United States, said the main fruits of his discoveries were yet to be enjoyed and that it was too early to say exactly what could be learned about the universe through his method.
"The real excitement is that I cannot answer that question yet," he said. "This is just an introduction to the science, the astronomy is still to come."
WINNERS FROM EINSTEIN TO BOHR AND THE CURIES
The winners of the Nobel physics prize are selected by the Royal Swedish Academy and receive a prize sum totalling 12 million Swedish crowns ($1.2 million), which is shared among the winners if there are several.
The Nobel Prizes were established under the will of Swedish inventor and entrepreneur Alfred Nobel, whose fortune was built in part on the invention of dynamite.
Physics occupied a prominent place in Nobel's will and the prize remains one of the discipline's highest distinctions. Over the decades, it has recognised discoveries that have fundamentally reshaped humanity's understanding of the universe.
Among past laureates are some of the most celebrated figures in science, including Albert Einstein, Marie and Pierre Curie, Max Planck and Niels Bohr, whose work helped establish the foundations of modern physics.
Last year's physics prize was awarded to US-based scientists John Clarke, Michel Devoret and John Martinis for experiments that demonstrated the principles of quantum physics in action, research seen as helping to advance the next generation of computing and other digital technologies.
Nobel medals are presented by Sweden's King Carl XVI Gustaf at a ceremony in Stockholm on December 10, the anniversary of Alfred Nobel's death. The awards are followed by an elaborate banquet at Stockholm City Hall.
The peace prize, the only Nobel not presented in Sweden, is awarded separately in Oslo.
($1 = 10.0329 Swedish crowns)
(Reporting by Niklas Pollard, Marie Mannes and Johan Ahlander in Stockholm; additional reporting by Simon Johnson, Anna Ringstrom and Greta Rosen Fondahn in Stockholm, and Terje Solsvik in Oslo; Editing by Alex Richardson and Kevin Liffey)
