Belgian-born physicist wins Nobel prize for work on neutrino ‘ghost particles’

Francis Halzen honored for building Antarctic lab to study tiny, mysterious cosmic particles with no electrical charge and extraordinarily small mass

This handout photo taken on April 13, 2023, and released on October 6, 2026, shows Francis Halzen, UW–Madison Vilas Research Professor, speaking about the UW IceCube Neutrino Observatory Project at the University of Wisconsin-Madison. (Bryce RICHTER/University of Wisconsin/AFP)

STOCKHOLM (AP) — Belgian-born scientist Francis Halzen won the Nobel Prize in physics Tuesday for his efforts to demystify a rare group of neutrinos, tiny cosmic particles that researchers believe offer clues to how the universe evolved.

“It was a great surprise, and I obviously didn’t expect it,” Halzen said, speaking to the Nobel Physics Committee by phone from Italy, in a call broadcast at the news conference to announce the winner.

Halzen said it was predicted that he would win the prize, but the announcement still made him feel “strange.”

“I am working on a proposal, and I hope that this prize will help getting it approved,” he said to chuckles from the audience.

Neutrinos are tiny cosmic particles with no electrical charge and extraordinarily small mass, making them difficult to detect. Yet they are everywhere: They spew from stars like the sun, and trillions zip through our bodies every second.

Scientists cannot glimpse the mysterious ghost particles zooming around on their own. Instead, they measure what happens when the particles collide with other bits of matter, producing flashes of light or charged particles.

Halzen paved the way for a new kind of astronomy

The Nobel committee said Halzen’s work was instrumental to the construction of the IceCube Neutrino Observatory in Antarctica, which was designed to turn ice into a neutrino detector. The observatory helped scientists discover the first high-energy neutrinos from other galaxies.

A handout picture taken on November 9, 2010 released by the US National Science Foundation (NSF) on December 23, 2010 shows the IceCube lab on the the Antarctic tundra near the US Amundsen-Scott South Pole Station. (AFP PHOTO/HO/NSF/F. DECAMPS)

Halzen “realized that the ice at the South Pole could visualize these neutrino messengers” from the cosmos, committee member Eva Olsson said during the news conference. “People joined him in the quest for these neutrino messengers.” The neutrinos “opened the door to distant galaxies and tell us about the processes of exploding stars.”

Born in Belgium, the 82-year-old scientist is affiliated with the University of Wisconsin–Madison in the US, which operates the observatory. Efforts by The Associated Press to reach him were not immediately successful.

Halzen helped pull the curtain back on a rare gang of neutrinos that scientists say hold clues about the development of the universe.

“This experiment in the Antarctic is a revolutionary way of understanding the universe that we didn’t have before,” said Michael Moloney, chief executive officer for the American Institute of Physics.

In a post on social media, Belgian Prime Minister Bart De Wever said Halzen is the 11th Belgian to win a Nobel Prize.

De Wever called the award “impressive recognition for a lifetime dedicated to shedding light on the great mysteries of the cosmos through its smallest components.”

A representative from the IceCube Neutrino Observatory did not immediately return a request for comment. The University of Wisconsin–Madison did not immediately comment when reached by the AP.

Ellen Moons, secretary-general of the Royal Swedish Academy of Sciences, announced the award Tuesday in Stockholm. She is the first woman to head the prestigious academy and present the award.

FILE: Workers labor on the underside of the cosmic detector housed underground at the Jiangmen Underground Neutrino Observatory in Kaiping in southern China’s Guangdong province, October 11, 2024. (AP Photo/Ng Han Guan)

The prize money this year is 12 million Swedish kronor (about $1.2 million), whether for an individual, a small group of laureates or an organization.

Last year, three scientists won the Nobel Prize in physics for research on the strange behavior of subatomic particles called quantum tunneling that enabled the ultrasensitive measurements achieved by MRI machines and laid the groundwork for better cellphones and faster computers.

The announcements of this year’s prizes began Monday with the Nobel Prize in medicine being awarded to three scientists whose work led to a tool that uses light to help unravel how the brain works.

This week’s awards continue Wednesday with the chemistry prize and literature on Thursday. After Friday’s peace prize is awarded, the Nobel Memorial Prize in Economic Sciences will be announced Monday.

read more: