Nobel Physics Prize Awarded for Capturing “Ghostly” Particles From Deep Space

The 2025 Nobel Prize in Physics has been awarded to Belgian physicist Francis Halzen for his pioneering role in developing the IceCube Neutrino Observatory, a vast detector buried in Antarctic ice that has opened a new window onto the universe’s most extreme phenomena.

Announcing the prize in Oslo, the Royal Swedish Academy of Sciences described the discovery as being about “ghostly messengers from space” — a reference to neutrinos, the almost weightless subatomic particles that travel across the cosmos largely undisturbed by matter, gravity or magnetic fields.

Halzen, 82, who was born in Tienen, Belgium, and now holds US citizenship as a professor at the University of Wisconsin–Madison, was honoured for his “decisive contributions” to building IceCube and for the subsequent discovery of high-energy neutrinos originating from deep in the universe.

A Telescope Made of Ice

IceCube is not a conventional telescope. It is a cubic kilometre of Antarctic ice at the South Pole, embedded with thousands of light sensors designed to detect the extremely faint flashes produced when a neutrino occasionally collides with an atom in the ice.

Because neutrinos pass through almost everything without changing course or losing energy, they carry information about violent cosmic events — such as exploding stars or matter being consumed by black holes — that cannot be obtained through light or other forms of radiation.

“Cosmic neutrinos with extremely high energies are very rare, so an enormous volume of ice is needed to observe an adequate number of collisions,” the Nobel committee explained in its citation.

Halzen first proposed the concept behind the observatory in 1988. Early testing followed a few years later, but the full-scale IceCube facility was only completed in 2011, the result of decades of sustained international collaboration.

“Courageous People” Behind the Project

Speaking to reporters by telephone shortly after the announcement, Halzen said he had not expected the honour.

“It was a great surprise, and I obviously didn’t expect it. But it’s a great pleasure to hear about this prize,” he said.

He was quick to credit the scientists who backed the ambitious and unconventional project in its earliest, most uncertain stages.

“For me, the main pleasure of it, besides winning the Nobel Prize, is that I hope this reflects on the really courageous people who joined me in the beginning of this project,” Halzen said.

Belgian Prime Minister Bart De Wever congratulated Halzen as the country’s 11th Nobel laureate and only its second in physics, calling his career “an impressive recognition of a life dedicated to unravelling the greatest secrets of the cosmos through its most minuscule manifestations.”

Could Neutrinos Carry Messages From Aliens?

Asked whether high-energy neutrinos might one day reveal signals from distant civilisations, Halzen acknowledged the idea has circulated in scientific circles but said he preferred to stay grounded.

“It has been speculated that this would be an ideal way to communicate with aliens,” he said. “But I don’t think I will go there. I think we have enough realistic problems to deal with right now.”

Nobel Season Continues

The physics prize is the second of this year’s Nobel announcements, following Monday’s medicine prize awarded to US psychiatrist and neurologist Karl Deisseroth, along with German scientists Peter Hegemann and Georg Nagel, for their work on optogenetics — a technique that allows nerve signals to be controlled using light.

The chemistry prize follows on Wednesday, with literature to be announced on Thursday and the closely watched peace prize on Friday. The economics prize rounds off the 2025 Nobel season on 12 October.

Each prize comes with a diploma, a gold medal and a 12-million-kronor (roughly R20-million) cash award, shared among winners where more than one laureate is named in a category. Laureates will formally receive their prizes at a ceremony on 10 December, marking the anniversary of the 1896 death of Alfred Nobel, the Swedish industrialist who established the awards.

Source: Nobel physics prize honours work on ‘ghostly messengers’ from outer space — eNCA