Halzen Wins Nobel for South Pole Ghost Particles

Neutrinos are extremely light particles that pour out of stars, including the Sun. Trillions pass through a person's body every second. Researchers call them ghost particles because they almost never strike ordinary matter, so they can cross dense regions that light cannot easily penetrate. With no electric charge, magnetic fields do not bend their path, and that direction can point back to a source. Halzen described a South Pole detector in 1988. IceCube uses one cubic kilometre of clear Antarctic ice, with thousands of light sensors buried in the sheet. If a neutrino hits an atomic nucleus, the impact creates fast charged particles. They rush through the ice and emit a blue glow. Scientists read the glow's shape and its arrival time to judge where the neutrino came from. Those collisions are so uncommon that only a huge block of ice records enough of them.

Halzen said the honour surprised him. On a phone call from Italy, broadcast at the news conference, he told the committee he had not expected the prize and that the news felt strange. He is working on a proposal and hopes the award will make approval easier. He also described his luck: when the project started, very few people, including Halzen himself, believed it would succeed. The prize money is 12 million Swedish kronor, roughly 1.2 million dollars. Neutrino energies can reveal how exploding stars, and the space around giant black holes, accelerate particles to extraordinary energies. Louis Barson, science director at London's Institute of Physics, said IceCube lets astronomers examine energetic events that ordinary telescopes cannot see. Oxford physicist Subir Sarkar said Halzen had opened a new window on the universe.