Physicist Francis Halzen wins 2026 Nobel Prize in Physics for 'ghost particle' work

The Royal Swedish Academy of Sciences announced on Tuesday that the 2026 Nobel Prize in Physics has been awarded to Belgian physicist Francis Halzen, recognizing his central role in building the IceCube Neutrino Observatory in Antarctica — a vast detector designed to catch neutrinos, the so-called "ghost particles" from space that scientists believe could offer clues about the evolution of the universe.

Speaking by phone from Italy in a call broadcast live at the prize announcement press conference, Halzen said: "It's a big surprise, and obviously I didn't expect this." He said he had previously been tipped to win a Nobel Prize, but the announcement still felt "strange" to him.

"I'm working on a proposal, and I hope this prize will help get that proposal approved," the 82-year-old physicist said, drawing laughter from the room.

Messages from the cosmos

According to the Royal Swedish Academy of Sciences, the neutrino interactions captured by the observatory provide information about how high-energy neutrinos form and may even reveal previously unknown phenomena.

Neutrinos have almost no mass and carry no electric charge, allowing them to pass through planets, stars and the human body without being altered. That very property makes them rare and hard to catch. An estimated 100 trillion neutrinos from the Sun and the cosmos pass through the human body every second.

Halzen first proposed the IceCube project in 1988, when he realized that the transparent ice beneath Antarctica could serve as a detector. In the rare event that a neutrino collides with an atomic nucleus, it produces a flash of light that sensors buried deep in the ice can register.

Richard Fitzgerald, editor-in-chief of Physics Today, noted that although hundreds of people took part in building the observatory, the project "started with one person." He also pointed out that the Nobel Prize in Physics in recent years has rarely gone to a single individual.

"Everyone joined him on the journey to search for these neutrino messengers. These messengers carry information from the universe," academy member Eva Olsson said at the press conference. "They have opened a door to distant galaxies and told us about processes inside exploding stars."

Eva Lindroth, a researcher in Stockholm and a member of the Nobel Committee, told Al Jazeera that Halzen's observatory has helped scientists better understand high-energy particles. "The interesting thing about neutrinos is that they come straight to us," she said. "Thanks to that, we can finally understand these sources of high-energy particles, and learn more about how entities in the universe form, such as how galaxies form and the role of black holes in that process."

Lindroth added: "It offers a new way to study the universe. They give us information we could not obtain any other way."

Last year's prize went to John Clarke, Michel Devoret and John Martinis for experiments in quantum physics.

On Monday, the Nobel Prize in Medicine was awarded to two American scientists for discoveries that help explain how the brain works. The Nobel Prize in Chemistry will be announced next on Wednesday in Stockholm.

Nobel laureates will receive their awards at a ceremony on December 10, marking the anniversary of the death of Swedish chemist Alfred Nobel, the founder of the prizes, with members of the Swedish and Norwegian royal families in attendance.