Francis Halzen wins the physics Nobel for the ice telescope at the South Pole

Francis Halzen won the 2026 Nobel Prize in Physics on Tuesday for building a telescope out of Antarctic ice. The Royal Swedish Academy of Sciences cited his decisive contribution to the IceCube Neutrino Observatory and the detection of high-energy neutrinos from outside the solar system. He is the sole laureate. The prize is 12 million Swedish crowns, about 1.2 million dollars, and will be handed over in Stockholm on 10 December. A single name on the physics medal is unusual. The prize is often split three ways. The academy's wording puts the vision and the leadership on Halzen and leaves the collaboration off the citation.

Halzen is 82. He was born in Belgium and is a professor at the University of Wisconsin-Madison, and a US citizen. He first set out the South Pole idea in 1988. IceCube was completed in 2011 beside the Amundsen-Scott station. The instrument uses a cubic kilometre of ice, with strings of sensors running down to about 2,500 metres. More than 5,000 optical modules watch for the faint blue flash, called Cherenkov light, that a neutrino makes when it hits an atom in the ice. The array records about one such event a day. The ice has to be clear enough for that flash to travel to a sensor. The South Pole sheet, laid down over millennia with little dust, is the reason the site works. A temperate glacier would scatter the light.

Neutrinos barely interact with matter. They cross the Earth without leaving a track that an ordinary telescope can see, which is why physicists call them ghost particles. That same indifference is why they are useful. Light from the centre of a galaxy can be blocked by dust. A neutrino from the same explosion arrives with its direction and energy almost intact. Eva Olsson of the academy said at the announcement that the particles open the door to distant galaxies and tell us about the processes of exploding stars. The 2013 result, a flux of high-energy neutrinos that could not be explained by atmospheric background, is the measurement the prize rests on. Later events have been tied to individual sources, including a flaring blazar. Many arrivals still cannot be pinned to a single object.

Halzen told the press conference he had expected the call and had spent previous Octobers unhappy that his collaborators had not been recognised. He said it was a relief, because around this time of year he had felt miserable that he had not won and that the people who built the instrument had not been recognised. He also said he had been lucky. When the project started, he said, very few people thought it would work, including himself. Mark Pearce, chair of the Nobel committee for physics, said Halzen had led the international team of researchers and engineers that built the instrument. Halzen's own line was that catching the particles in ice had been the goal, and that the result opens a window that is not yet ordinary astronomy.

He said it will take bigger telescopes, many more telescopes, to become real astronomy. The planned extension, IceCube-Gen2, is aimed at 2033 and would instrument about eight cubic kilometres of ice, eight times the present volume. Until that ice is drilled, the operating instrument remains a one-neutrino-a-day array at the bottom of the polar cap, maintained by a collaboration the medal does not name. The 12 million crowns go to Halzen. The sensors stay in the ice.