The Royal Swedish Academy of Sciences has announced the 2026 Nobel Prize in Physics. It goes to Francis Halzen, principal investigator of the IceCube Neutrino Observatory and professor at the University of Wisconsin–Madison. The citation reads: "for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin."
The prize is not about one person alone. Halzen himself stresses that the project's success came from the hard work of many colleagues. Still, he proposed the key idea and was a driving force behind forming the collaboration and building the observatory.
What the prize recognises
Halzen proposed, and then showed, that ice can serve as a detection medium for high-energy neutrinos from space. Neutrinos are elementary particles that interact extremely weakly with matter, and they offer a new way to study the Universe. Humanity has long done astronomy with visible and invisible light. Now neutrinos can be used as well.
Putting a detector in ice was a bold idea. Building, operating and doing science with IceCube is described in the source as a technological tour de force. The observatory instruments a cubic kilometre of pristine glacial ice at the South Pole. The international collaboration includes more than 450 scientists from 58 institutions in 14 countries. They study the characteristics and origin of astrophysical neutrinos, cosmic rays and neutrino properties, and they search for physics beyond the Standard Model.
What was known before
In 2013 IceCube discovered a flux of astrophysical neutrinos. Where they came from was not known at the time. Since then the collaboration has reported evidence of neutrino emission from two galaxies: TXS 0506+056 and NGC 1068, also known as Messier 77. In 2023 IceCube also announced the discovery of neutrinos from our own galaxy, the Milky Way.
For the two galaxies the source speaks of "evidence", not final confirmation. IceCube spokesperson Erin O'Sullivan says Halzen continues to inspire colleagues to move from the first discoveries to robust detections. The field is only starting to move from its first stage to the next.
It's a great relief for me to finally deliver the recognition that this great collaboration deserves.Francis Halzen, IceCube principal investigator
What comes next
In 2019 the U.S. National Science Foundation, together with U.S. institutional and international partners, approved funding for the IceCube Upgrade. Seven years later it has been deployed. It is the first significant expansion of IceCube since its completion 15 years ago.
The upgrade is meant to lower the energy threshold at which the detector registers neutrinos. It will also help calibrate the ice better. Together, this should improve reconstruction of the direction a particle came from. First science data from the IceCube Upgrade are expected later this year.
Further ahead is the proposed IceCube-Gen2. It includes an optical array with a volume 8 times larger and a radio detection technique. The radio method would measure astrophysical neutrinos of even higher energies.
Who supports the observatory
IceCube is funded and operated primarily through an award from the U.S. National Science Foundation to the University of Wisconsin–Madison. Research is supported by agencies in Australia, Belgium, Canada, Denmark, Germany, Italy, Japan, New Zealand, the Republic of Korea, Sweden, Switzerland, Taiwan, the United Kingdom and the United States. Construction also received significant contributions from funders in Belgium, Germany, Korea, Japan and Sweden, as well as Michigan State University.
