// WIRED US/UK — SALUTE
A Scientist Working on the ‘IceCube’ Neutrino Detector Explains the Nobel Prize–Winning Technology
“for some reason, I woke up at 5:30, and the first thing I did was go to the New York Times website to check the headlines,” Juan Carlos Díaz Vélez recalls of the previous morning. “To my great surprise, there was a breaking news story: Francis Halzen had just been awarded the Nobel Prize in Physics. I immediately started sending messages, only to discover that my colleagues in Europe had found out long before I did.”
Juan Carlos Díaz Vélez works at the Wisconsin IceCube Particle Astrophysics Center at the University of Wisconsin–Madison. The new Nobel laureate is his boss.
“When I arrived at the WIPAC offices, everyone was smiling and congratulating one another,” Díaz Vélez says. “We gathered in the conference room to watch the press conference with Francis Halzen, who was in Italy at the time attending a conference. We’ll wait for his return to celebrate, and in the meantime, we’ll keep working on the neutrino study, because this work never ends.”
That work is detecting an elusive particle using detectors inside a big block of ice.
Professor Francis Halzen of the University of Wisconsin–Madison joined virtually from Italy to share the news that he had won the 2026 Nobel Prize in Physics.
“Neutrinos are subatomic particles that participate in reactions within the nuclei of atoms,” Díaz Vélez explains. “They are produced by radioactivity on Earth—and even in watermelons and bananas, due to their potassium-40 content—as well as in our own bodies.”
Not that any of us notice. These particles do not interact easily with matter. As their name suggests, neutrinos have no electric charge, so they can travel through space in a straight line without being affected by magnetic fields, and they constantly pass through the entire Earth without interacting with a single atom. “Neutrinos from the sun are so abundant that 1 billion of them pass through the nail of a thumb every second,” Díaz Vélez says.
The neutrinos studied by Halzen’s team are not the run-of-the-mill particles we’re encountering constantly—if unknowingly. They are interested in very high-energy neutrinos that come from deep space. These cosmic particles may originate from supernova remnants or even black holes. The intense magnetic fields of such phenomena can accelerate particles like protons to very high energies.
“When these particles collide with the interstellar medium—which consists of gas and plasma—they produce gamma rays and neutrinos,” Díaz Vélez says. “That is why neutrinos are perfect messengers from high-energy cosmic-ray sources. The highest-energy neutrino sources we have detected come from active galactic nuclei, which contain supermassive black holes.”
And the team Díaz Vélez is part of has detected such neutrinos at a facility located at the geographic South Pole known as the IceCube Neutrino Observatory—no relation to the famous rapper. The observatory contains an array of 5,160 optical sensors buried deep underground, covering 1 cubic kilometer of ice.