University of Wisconsin–Madison physics professor Francis Halzen has won the Nobel Prize in physics for his work developing the IceCube Neutrino Observatory, a research project that uses Antarctic ice to detect neutrinos from some of the universe’s most energetic events. Halzen was in Italy writing a proposal when he received the call Tuesday. He joined a UW–Madison news conference remotely, where colleagues and supporters celebrated his award. The Nobel Prize, awarded by the Royal Swedish Academy of Sciences, comes with about $1.2 million. IceCube is embedded in a cubic kilometer of Antarctic ice. Thousands of light sensors detect signals produced when neutrinos — nearly massless particles that rarely interact with other matter — pass through the ice. Studying the particles can help researchers investigate black holes, galaxies and other cosmic objects. Halzen is the observatory’s principal investigator. The National Science Foundation funds the project, which is operated by an international research collaboration led by the Wisconsin IceCube Particle Astrophysics Center at UW–Madison. The idea took shape at UW–Madison in the late 1980s. In 2013, IceCube detected high-energy neutrinos originating beyond the solar system, a breakthrough that opened a new avenue for exploring the cosmos. Dan Hooper, a UW–Madison physics professor and director of the IceCube center, said the scale of the proposed observatory once seemed nearly impossible. Halzen’s persistence, he said, turned the concept into a working instrument and helped establish a field of research. Halzen credited the project’s progress to the many researchers involved, along with persistence, talent and some good fortune. He also pointed to UW–Madison’s willingness to support ambitious research and its Physical Sciences Laboratory in Stoughton as important to IceCube’s development. Born in Belgium, Halzen joined the university’s physics faculty in 1972. He is the sixth physicist connected to UW–Madison to receive a Nobel Prize and the 23rd laureate associated with the university overall. The last UW–Madison faculty member to win a Nobel was Howard Temin, who received the 1975 prize for work on reverse transcriptase. The award marks a milestone for the university and Wisconsin’s research community, said Renée Wachter, interim president of the Universities of Wisconsin. Halzen said he plans to celebrate quietly at his hotel in Italy, where he is attending physics committee meetings.