Nobel Prize in Physics 2026: Catching Ghost Particles Under Antarctic Ice
Francis Halzen won for his role in the IceCube Neutrino Observatory, a detector buried in Antarctic ice. Learn what neutrinos are and why catching them opens a new window on the universe.
The 2026 Nobel Prize in Physics, announced on 6 October, was awarded to Francis Halzen, a Belgian-American particle physicist, for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.
What is a neutrino?
A neutrino is a tiny particle with almost no mass and no electric charge. It barely interacts with anything. Trillions of them pass through your body every second, mostly from the Sun, and you feel nothing. They are sometimes called "ghost particles".
Why do scientists want to catch them?
Light and other particles can be blocked or bent on their way from space. Neutrinos fly in a nearly straight line from violent events, such as exploding stars and the regions around supermassive black holes, and pass through almost everything. If we can detect them, we can learn where they came from and what happened there.
How IceCube works
A giant detector in ice
IceCube is built in the clear ice of the South Pole, where about one cubic kilometre of ice is instrumented.
Thousands of sensors
Strings of light sensors were lowered deep into holes drilled in the ice, more than a kilometre below the surface.
A rare collision
On very rare occasions, a neutrino hits an atom in the ice.
A flash of blue light
The collision creates charged particles that emit a faint glow as they move through the ice.
The sensors record it
By comparing when different sensors see the light, scientists work out the neutrino's direction and energy.
Milestones
- 2013: IceCube reported the first evidence of high-energy neutrinos arriving from outside our solar system.
- 2017: A high-energy neutrino was traced back to a distant galaxy with a very active black hole, a type called a blazar. It was one of the first times a neutrino was linked to a specific cosmic source.
- 2023: IceCube scientists reported neutrinos coming from our own Milky Way galaxy.
Why the South Pole?
The deep Antarctic ice is extremely clear, very quiet, and stable, which makes it a perfect natural detector.
What most people miss
- A neutrino detector is a telescope. It points at the sky, in this case through the whole Earth, because neutrinos travel straight through the planet.
- This is team science. IceCube involved hundreds of scientists from many countries over decades.
- Neutrinos still hold puzzles, such as their exact masses and why there is more matter than antimatter in the universe.
