The Royal Swedish Academy of Sciences has awarded the 2026 Nobel Prize in Physics to Francis Halzen of the University of Wisconsin–Madison for his decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.
Halzen realised that Antarctic ice could be used to detect and track neutrinos, elusive particles that usually pass through the Earth and the human body without leaving a detectable trace. His scientific vision and leadership were instrumental in the development of IceCube, an observatory consisting of a cubic kilometre of Antarctic ice equipped with light sensors.
Extremely high-energy neutrinos are produced in some of the universe’s most violent environments. Unlike many other particles, they can travel vast distances without being deflected or losing substantial energy, allowing scientists to trace them back to distant cosmic sources that are otherwise difficult to study.
Halzen first proposed using the ice at the South Pole to detect neutrinos in 1988. When a neutrino occasionally collides with an atomic nucleus, the interaction produces a flash of light that can be detected by sensors embedded in the clear glacial ice.
The IceCube Neutrino Observatory was completed in 2011. Researchers subsequently detected high-energy neutrinos and established that some originated far beyond the solar system, opening a new avenue for identifying the sources of some of the universe’s most energetic processes.
“Francis Halzen has led an international team of researchers and engineers who have provided us with a fantastic instrument,” Mark Pearce, Chair of the Nobel Committee for Physics, said. He added that Halzen’s tenacity and scientific vision had paved the way for a new form of astronomy.
The academy said continued observations by IceCube could provide new insights into the extreme environments in which high-energy neutrinos are created and could potentially reveal previously unknown cosmic phenomena.
Halzen was born in Tienen, Belgium, in 1944 and received his PhD from KU Leuven in 1969. He is a professor at the University of Wisconsin–Madison.
The 2026 Nobel Prize in Physics is worth SEK 12m, or about $1.2m.
