4 min readOct 7, 2026 01:40 PM IST First published on: Oct 7, 2026 at 01:36 PM ISTFor an astronomer, light is the easy part: Hold up a lens or a mirror and starlight is yours. Neutrinos are another matter. Born in the most violent places in the cosmos, these ghost-like particles pass through planets, people and most detectors almost without a trace. It took decades to turn a cubic kilometre of Antarctic ice into a telescope for these deep-space messengers. This year’s Nobel Prize in Physics goes to the man who stayed with that hunt: Francis Halzen, a Belgian-born physicist at the University of Wisconsin–Madison.Why chase a particle so hard to catch in the first place? “You could see things in the universe you couldn’t see any other way,” Halzen once said in an interview. Neutrinos barely interact, so they escape from deep inside their sources while light gets stuck on the way out. Think of a journalist trying to reach the one official who was in the room where a major policy was made. The press conference is easy to attend; that is astronomy with visible light. But the insider who knows what was really decided avoids reporters. Catching a neutrino is harder still.AdvertisementAlso Read | In Nobel Prize for medicine, a single cell, a flash of light, a breakthroughThe gigantic IceCube Neutrino Observatory near the Amundsen-Scott South Pole station in Antarctica has lowered 86 cables into the ice, the deepest reaching almost 2.5 kilometers down. To place them, scientists had to melt holes in the ice with hot water. Each cable sports sixty sensitive light detectors, like beads strung on a thread. On rare occasions, a neutrino strikes a nucleus of an atom in the ice, and the collision generates high-energy particles. The resulting particles move faster than light travels in ice, and generate an eerie, bluish flash, much like a sonic boom of a supersonic jet. That glow, the signature of a far traveling neutrino, is what the sensors on the strings pick up.Such an instrument couldn’t be built overnight. What Halzen himself once called a “cute idea” took smaller trials to hone the skill and show what a larger detector could potentially deliver. Conceived in the 1980s, the last cable in IceCube was dropped in 2010. Since then, it has been eavesdropping on far-away violent phenomena in the universe. Some strange galaxies, unlike our own Milky Way, host massive black holes that churn the gas in their cores and spew spectacular jets. These jets accelerate high energy particles called cosmic rays, which collide and produce neutrinos. These neutrinos point back to where cosmic rays are produced.The discoveries at IceCube have been helping astronomers to peek inside the core of these galaxies. In 2017, a single neutrino hurtled through the observatory, and its path indicated it was coming from the direction of the constellation Orion. Alerted astronomers worldwide swiveled their telescopes in that direction and found a “blazar”, a giant galaxy whose central black hole, weighing hundreds of millions of suns, spits out a jet aimed straight at Earth.AdvertisementThe discovery gave a major boost to “multi-messenger” astronomy, where scientists use visible light, neutrinos, and gravitational waves to study the same cosmic event, pulling together the clues from “all the light we cannot see”. IceCube has also confirmed a prediction from the 1960s about how an antineutrino interacts with an electron.you may likeHalzen, the principal investigator of this unique venture, has long been drawn to astroparticle physics, the area of research that marries astronomy with particle physics. Born in 1944, he studied at KU Leuven, Belgium, where he completed his master’s degree and PhD. Then, while working at CERN, Geneva, in early 1970s, he was invited to the University of Wisconsin-Madison, where he has been since. But IceCube was never a one-man project: It is the work of an international collaboration of hundreds of scientists and engineers.Starlight can be caught with a mirror. Neutrinos take patience. IceCube received its first major expansion only this year, and physicists are already proposing a successor eight times its size. Somewhere out there, another neutrino is on its way. Thanks to Halzen and his team, the ice is ready.The writer, visiting professor, IISER Mohali, was an astrophysicist at the Raman Research Institute, Bengaluru