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Yuya Makino/IceCube/NSFBelgian physicist Prof Francis Halzen has won the Nobel Prize in Physics for his pioneering work on an observatory that detects particles from space, shedding light on the distant universe.
Halzen led the development of IceCube at the South Pole, which uses a cubic kilometre of Antarctic ice fitted with light sensors to detect particles called neutrinos. These carry information about violent, high-energy processes in the cosmos.
The Royal Swedish Academy of Sciences said “his vision and scientific leadership have been fundamental for the IceCube Neutrino Observatory”.
Halzen first presented his vision for detecting neutrinos at the South Pole in 1988.
Halzen told a news conference that he was surprised his idea worked so well.
“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.”
Neutrinos are elusive subatomic particles. The Sun produces vast numbers of them: every second, billions pass harmlessly through an area the size of your fingernail.
But IceCube is searching for much higher-energy neutrinos, those produced by violent processes far beyond our Solar System — in distant galaxies.
It is composed of thousands of sensors on long cables that are drilled and frozen into a 1km cubic block of ice.
Neutrinos can be thought of as astronomical messengers that point to those fundamental events.
At the observatory, most neutrinos pass straight through the ice, but occasionally one interacts with it, producing particles that give off a telltale flash of light.
These rare signals carry clues to where the neutrinos came from and the extreme conditions that produced them — allowing scientists to investigate places that ordinary telescopes cannot easily see.
“Francis Halzen has led an international team of researchers and engineers who have provided us with a fantastic instrument,” said Prof Mark Pearce, Chair of the Nobel Committee for Physics.
“His tenacity and scientific vision has paved the way for a new kind of astronomy.”
IceCube/NSFOn the rare occasions when a neutrino strikes an atomic nucleus, it produces fast-moving charged particles. It is these racing through the ice, which give off a blue glow, which sensitive light detectors can pick up.
The pattern and timing of that light allow scientists to estimate the direction the neutrino came from — helping them trace its origins in the cosmos. But these interactions are so rare that the observatory needed an enormous volume of clear ice.
Halzen’s idea was to use a vast natural ice sheet in Antarctica. So began an audacious plan to build a neutrino observatory at the geographic South Pole, with thousands of light sensors embedded deep in the ice.
