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This special colloquium marks the announcement on 6 October 2026 of the Nobel Prize in Physics awarded to Francis Halzen for his contributions to IceCube and the discovery of high-energy cosmic neutrinos.
It offers an introduction to the science behind this achievement and the observatory that made it possible.

The 2026 Nobel Prize in Physics awarded to Francis Halzen recognizes the realization of the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin. These particles offer a new way to study the most powerful cosmic accelerators, carrying information from environments that can be difficult to observe with light alone.

Buried in a cubic kilometer of Antarctic ice, IceCube detects the faint light produced by charged particles created in neutrino interactions. In this colloquium, I will explain how a detector at the South Pole became an astronomical observatory, how the cosmic neutrino signal was established, and what subsequent observations have revealed about its origins. Highlights will include the search for extragalactic neutrino sources and the emerging view of our own Galaxy through neutrinos.

I will also discuss the experimental challenges behind these discoveries and the next steps for the field, from the IceCube Upgrade to IceCube-Gen2. Photographs from my two South Pole deployment seasons will illustrate how the instruments are built and operated, connecting the scientific results to the international effort that makes them possible.