Francis Halzen, who today won the 2026 Nobel Prize in Physics, was the driving force behind IceCube, a pioneering neutrino observatory that occupies a cubic kilometre of ice in Antarctica.

But Halzen, whom I have had the privilege of interviewing many times while covering the field, never believed that neutrino detectors such as IceCube could work in isolation.

The promise of multimessenger astronomy

The dream of many neutrino researchers—and the ultimate story for some journalists—is to discover cosmic phenomena simultaneously with several types of observatories. This approach is known as multimessenger astronomy.

Increasingly sophisticated telescopes allow astronomers to observe the universe using electromagnetic signals across the spectrum, from long-wavelength radio waves to gamma rays, far beyond visible light.

Neutrinos and high-energy cosmic rays, which are mostly protons, provide another perspective. These particles allow researchers to study matter arriving from cosmic sources, rather than relying only on electromagnetic radiation. The idea is that conventional, or electromagnetic, astronomy is just one of several ways to build a complete picture of the universe.

Cosmic events such as a supernova explosion or a sudden burst of activity around a supermassive black hole should produce not only electromagnetic radiation, but also neutrinos and other matter particles.

IceCube’s 2017 neutrino breakthrough

IceCube made its first multimessenger discovery in 2017, when it detected a neutrino labelled TXS 0506+056, also known as “Texas”. Researchers successfully traced the high-energy neutrino to a galaxy containing a powerful source: a blazar that emits gamma rays.

That same year, astronomers observed an equally significant multimessenger event: a kilonova produced by the collision of two neutron stars. The kilonova was first identified through another cosmic messenger—the detection of gravitational waves, which are perturbations in the geometry of space.

I was fortunate enough to cover both the Texas event and the kilonova.