Francis Halzen wins 2026 Nobel Prize in Physics for turning Antarctic ice into a neutrino observatory

The Royal Swedish Academy of Sciences awarded Halzen the prize “for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.”

Neutrinos are extremely light particles that rarely interact with matter. Vast numbers pass through Earth - and through our bodies - without leaving any detectable trace.

Very occasionally, however, a neutrino collides with an atomic nucleus and produces charged particles whose passage creates a flash of light. Halzen realized that sensors embedded deep in the exceptionally clear ice at the South Pole could detect those flashes.

The resulting IceCube Neutrino Observatory contains light sensors buried between roughly 1,450 and 2,450 meters beneath the Antarctic surface and uses an entire cubic kilometer of ice as its detection volume. It was completed in 2011.

IceCube subsequently detected high-energy neutrinos originating far beyond the solar system, opening a new way to study some of the most violent and energetic processes in the universe.

Unlike electrically charged cosmic particles, which can be deflected by magnetic fields, neutrinos travel vast distances without significantly changing direction or losing energy. Scientists can therefore use them to trace otherwise difficult-to-study cosmic particle accelerators and investigate how extreme astrophysical phenomena work.

“His tenacity and scientific vision has paved the way for a new kind of astronomy,” Nobel Committee chair Mark Pearce said.

Halzen, 82, was born in Tienen, Belgium, earned his PhD from KU Leuven and is a professor at the University of Wisconsin–Madison. He first proposed using South Pole ice to detect neutrinos in 1988.

The prize is worth 12 million Swedish kronor.