Francis Halzen wins 2026 Nobel Prize in Physics for 'ghost particle' observatory buried in Antarctic ice

Francis Halzen was working on a research proposal in Italy when the call came from Stockholm. The Royal Swedish Academy of Sciences announced on Tuesday that the 82-year-old Belgian physicist had won the 2026 Nobel Prize in Physics — awarded for burying thousands of light sensors deep in Antarctic ice and using them to catch some of the rarest particles in the universe.

It was a great surprise, and I obviously didn't expect it.— Francis Halzen, Nobel laureate and professor, University of Wisconsin–Madison

The Academy awarded Halzen the prize 'for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.' The prize is worth 12 million Swedish kronor — roughly $1.2 million.

Neutrinos are subatomic particles with nearly no mass and no electric charge. They pass through planets, stars, and human bodies almost without a trace — which is why physicists call them ghost particles. Every second, around 100 trillion solar and cosmic neutrinos stream through each of us, and we feel nothing. Most come from the Sun, but a far rarer variety — roughly a billion times less common — originate from some of the most violent environments in the universe: the superheated regions around supermassive black holes, exploding stars, and other extreme cosmic accelerators.

Every second, without you noticing, 65 billion neutrinos from the Sun flow through your little fingernail.— Nobel Committee for Physics

What makes high-energy neutrinos so scientifically valuable is precisely what makes them so hard to catch. Unlike electrically charged cosmic rays, whose paths are bent by magnetic fields as they travel across the universe, neutrinos travel in nearly straight lines. That means they can point scientists directly back to their source — even when that source is hidden behind dust clouds or dense matter that blocks light entirely.

Halzen first presented his solution in 1988: use the ice at the South Pole itself as the detector. Deep beneath the surface, Antarctic ice is exceptionally clear and geologically stable, free from the interference that plagues other environments. His proposal was to drill narrow boreholes into it, lower long strings of light sensors more than a kilometre down, and let the holes refreeze — embedding the sensors inside an enormous natural detector.

The physics works like this: when a high-energy neutrino very occasionally strikes an atomic nucleus in or near the ice, it produces a charged particle — a muon — that travels through the ice faster than light moves through ice (though still slower than light in a vacuum). That produces a faint cone of blue light known as Cherenkov radiation. By measuring the timing and pattern of that light across many buried sensors, IceCube can reconstruct the muon's path and work backwards to infer where the original neutrino came from.

The idea was first developed into a prototype called AMANDA — the Antarctic Muon And Neutrino Detector Array — built 1.5 kilometres deep at the Amundsen-Scott South Pole Station in 1995. By 2010–2011, AMANDA had grown into IceCube: a full cubic kilometre of instrumented ice, the largest neutrino telescope ever built. Within a few years of completion, IceCube confirmed the first high-energy neutrinos from beyond the solar system, and then published the discovery of neutrinos that must have originated far outside our galaxy.

A landmark came in September 2017, when IceCube provided the first evidence pinpointing a source of high-energy cosmic rays — particles whose origins had eluded scientists since their discovery more than a century ago, according to the National Academy of Sciences. The neutrino detected had an energy of about 300 trillion electron volts — more than 45 times what is achievable at CERN's Large Hadron Collider. NASA's Fermi Space Telescope later traced it to a supermassive black hole, and found it had travelled approximately 3.7 billion light-years at nearly the speed of light before being caught in the Antarctic ice.

The nice thing with neutrinos is that they come straight at us. That way we can ultimately understand these sources of high-energy particles and understand more about how things in the universe, like how galaxies are formed and the roles of the black holes in that process.— Eva Lindroth, researcher and member of the Nobel Committee

IceCube's detections have helped establish what scientists now call multimessenger astronomy — building a fuller picture of the universe by combining neutrino measurements with data from conventional telescopes and gravitational wave detectors. Each type of signal carries different information; together, they can triangulate and scrutinise distant phenomena that no single instrument could resolve alone.

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.— Mark Pearce, Chair of the Nobel Committee for Physics

The award to a single individual is itself notable. Richard Fitzgerald, editor-in-chief of Physics Today, observed that while hundreds of people built the observatory, it 'all started with one person,' and noted that the physics prize has rarely gone to a sole winner in recent years. The last time it did was in 1992, when French physicist Georges Charpak received it alone, according to Scientific American. Halzen himself, reached by phone in Italy, was quick to deflect the credit.

I hope this reflects on the really courageous people who joined me in the beginning of this project.— Francis Halzen, Nobel laureate

The recognition arrives at a fraught moment for the kind of large-scale, publicly funded science IceCube represents. The Trump administration's budget proposal for 2027 calls for halving IceCube's funding, according to Scientific American. Halzen, characteristically, said he hoped the Nobel would help him get his current research proposal approved — drawing laughter from the audience at the announcement press conference.

IceCube has already inspired successors. The KM3NeT — a cubic-kilometre neutrino telescope being built at the bottom of the Mediterranean Sea — has already detected the most energetic neutrinos ever seen, according to IFLScience. Similar detectors have been proposed by China. The field Halzen seeded in the Antarctic ice is now spreading across the planet's oceans.

Halzen was born in 1944 in Tienen, Belgium, and received his PhD in 1969 from KU Leuven. He is a professor at the University of Wisconsin–Madison, where he has been principal investigator of IceCube. Nobel laureates will receive their awards in Stockholm on December 10, the anniversary of Alfred Nobel's death.

Why it matters — IceCube gave humanity a fundamentally new way to observe the universe — and the Nobel recognition lands just as the project faces proposed US funding cuts that could curtail the field Halzen built.

Reported by kva.se, reuters.com, nobelprize.org, scientificamerican.com, nytimes.com, theprint.in, theconversation.com, aljazeera.com, iflscience.com