Belgian physicist Francis Halzen has won the Nobel Prize in Physics for his decisive contribution to developing the IceCube Neutrino Observatory, a giant detector buried beneath the Antarctic ice that allows scientists to study some of the most violent events in the universe.
Halzen led the development of IceCube at the South Pole, where thousands of light sensors are embedded in a cubic kilometre of Antarctic ice. The observatory detects elusive subatomic particles called neutrinos, which can travel across vast cosmic distances carrying information about extreme events that conventional telescopes cannot easily observe.
The Royal Swedish Academy of Sciences said Halzen’s “vision and scientific leadership have been fundamental” to the IceCube Neutrino Observatory.
IceCube turns Antarctic ice into telescope
Halzen first presented his idea for detecting neutrinos at the South Pole in 1988. The concept relied on using the enormous natural ice sheet in Antarctica as a detector.
“I have to emphasise how lucky I was. Because when we started this project, everybody realised this was maybe a good idea, but very few thought it would work, including myself,” Halzen said at a news conference.
IceCube consists of thousands of sensors installed on long cables drilled deep into roughly 1km of Antarctic ice. Most neutrinos pass through the ice without interacting with it. On rare occasions, however, a neutrino collides with an atomic nucleus, producing fast-moving charged particles.
These particles generate a faint blue flash as they travel through the ice. IceCube’s sensitive detectors capture the light, while its timing and pattern help scientists estimate the direction from which the neutrino arrived.
Prof Mark Pearce, chair of the Nobel Committee for Physics, said Halzen had led an international team of researchers and engineers that created “a fantastic instrument”.
“His tenacity and scientific vision has paved the way for a new kind of astronomy,” Pearce said.
Ghost particles open a new window on cosmos
Neutrinos are produced in enormous numbers by the Sun. Billions pass through an area roughly the size of a human fingernail every second without causing harm.
IceCube, however, is designed to detect far more energetic neutrinos originating from violent processes beyond our Solar System, including distant galaxies and environments surrounding massive black holes.
Their unusual properties make neutrinos valuable astronomical messengers. Because they rarely interact with matter, they can pass through dense regions that light cannot penetrate. Their lack of electric charge also means magnetic fields do not bend their paths, allowing scientists to trace their arrival direction back towards potential cosmic sources.
The energy carried by the particles provides further clues about the extreme processes that produced them, including mechanisms that accelerate particles to extraordinary energies.
IceCube has therefore enabled scientists to study parts of the universe that remain difficult or impossible to investigate using conventional electromagnetic telescopes.
Louis Barson, director of science at the Institute of Physics in London, said the observatory had opened a “remarkable” new window on the universe.
“The discoveries that have followed are helping us understand some of the most energetic and mysterious processes in the universe – and that’s thanks to Professor Halzen’s work,” Barson said.