What are 'ghost particles' that pass through your body every second? Francis Halzen wins Physics Nobel for catching them in South Pole ice

Belgian-born physicist Francis Halzen has won the 2026 Nobel Prize in Physics for turning a cubic kilometre of Antarctic ice into a telescope that catches "ghost particles" from the most violent corners of the universe.

The Royal Swedish Academy of Sciences announced the award on Tuesday. Halzen, 82, of the University of Wisconsin-Madison, is honoured for his decisive role in the IceCube Neutrino Observatory and the discovery of high-energy neutrinos that come from beyond our Solar System. The prize carries 12 million Swedish kronor.

Also read: Nobel Prize in Physics 2026 awarded to Francis Halzen for work on ghost-like cosmic messengers


According to the Academy, Halzen first presented his vision for capturing neutrinos at the South Pole in 1988. Mark Pearce, Chair of the Nobel Committee for Physics, said his tenacity and scientific vision have paved the way for "a new kind of astronomy".

Why neutrinos are called ghost particles

Neutrinos are tiny subatomic particles that barely interact with matter. The Sun produces vast numbers of them, and billions pass through an area the size of a fingernail every second without leaving a trace.

The neutrinos IceCube hunts are far more energetic. They are produced by extreme events in distant galaxies, such as matter falling into supermassive black holes.

They matter because they carry a cosmic address. Cosmic rays, the charged atomic nuclei that constantly hit Earth's atmosphere, are bent by magnetic fields on the way, so their origin has been a mystery for over a century, the IceCube Collaboration notes in its research papers. Neutrinos carry no charge, so they travel in straight lines and point back to where they were born.

A telescope made of ice

IceCube sits near the Amundsen-Scott South Pole Station. Its light sensors hang on 86 cables, called strings, frozen into ice between 1.5 km and 2.5 km below the surface. Construction was completed in December 2010 after seven years of work. The project is backed by the US National Science Foundation, with the University of Wisconsin-Madison as the lead institution.

Almost all neutrinos pass straight through the ice. Once in a while, one strikes an atomic nucleus and sets off fast-moving charged particles that give off a faint blue glow. The sensors record the pattern and timing of that light, which lets scientists work out the direction and energy of the neutrino. Because such hits are so rare, the detector needed an enormous volume of clear ice.

Halzen, IceCube's principal investigator, told a news conference that he was lucky. "Very few thought it would work, including myself," he said.

From first signals to first sources

IceCube's results built up step by step:

• 2012: Two events with energies above a quadrillion electronvolts were spotted. Scientists nicknamed them Bert and Ernie.


• 2013: The IceCube Collaboration reported 28 high-energy events recorded between May 2010 and May 2012. Its paper in the journal Science said a purely atmospheric origin was rejected at the 4-sigma level, the first solid evidence for neutrinos from outside the Solar System.


• 2018: A neutrino of roughly 300 TeV was traced to the blazar TXS 0506+056, about four billion light years away. About twenty telescopes around the world joined the follow-up.


• 2022: IceCube reported evidence of neutrino emission from the nearby active galaxy NGC 1068, with about 80 neutrinos detected from its direction.


• 2023: A paper in Science reported neutrinos from the plane of the Milky Way at 4.5-sigma significance, using ten years of data and machine-learning techniques. It was the first observation of our Galaxy in a particle other than light.

What the prize recognises

Pearce said Halzen led an international team of researchers and engineers who gave science a fantastic instrument. The Academy said the neutrino interactions IceCube keeps collecting will offer new knowledge about the violent settings where such particles form, and could even reveal previously unknown cosmic phenomena.

Also read: 2026 Nobel Prize: Who is Francis Halzen and what is the IceCube Observatory?

The physics Nobel goes to individuals, while IceCube is the product of a large international collaboration. Scientists from India are part of it too. The Institute of Physics, Bhubaneswar, is among the institutions listed on the 2023 Milky Way paper.

IceCube scientists have proposed a successor, IceCube-Gen2. They say it could detect many more of these extreme particle accelerators and study them at even higher energies.

Halzen was born in 1944 in Tienen, Belgium, and earned his PhD at KU Leuven in 1969. He has been on the physics faculty at the University of Wisconsin-Madison since 1972. He co-wrote the textbook "Quarks and Leptons". Earlier this year he received the American Physical Society's Medal for Exceptional Achievement in Research.

His other honours include the 2015 Balzan Prize and the 2021 Homi Bhabha Medal and Prize of the International Union of Pure and Applied Physics.