A deep-sea telescope with a cosmic goal
Far beneath the Mediterranean Sea, European scientists are searching for answers about the Universe. Their tool is KM3NeT, a massive neutrino telescope anchored to the ocean floor. In 2023, it detected the most powerful neutrino ever recorded. That single event may help explain the most extreme forces shaping the cosmos.
KM3NeT does not look at stars or galaxies. Instead, it tracks tiny particles called neutrinos that race across space almost untouched. Because of this, they carry clean information from places no telescope can see.
What makes neutrinos so important
Physicists first proposed neutrinos in the 1930s, but they remained hidden for decades. Today, scientists know they are everywhere. Billions pass through your body every second without leaving a trace.
Neutrinos have almost no mass and no electric charge. As a result, they rarely interact with matter. That makes them very hard to catch. However, it also makes them extremely valuable.
Because neutrinos travel straight across the Universe, they act like messengers. They come from violent events such as exploding stars, black holes, and galaxy-scale collisions. Therefore, studying them helps scientists understand how the Universe works and why matter exists at all.
How KM3NeT detects the invisible
KM3NeT watches for rare moments when a neutrino finally hits something. When that happens, it creates a brief flash of blue light called Cherenkov radiation. The telescope sensors detect this light and record the event.
The detector uses hundreds of vertical lines anchored to the seabed. Each line holds glass spheres filled with sensitive light sensors. Together, they form a huge three-dimensional grid in the dark water.
Other observatories use similar methods. IceCube sits deep in Antarctic ice, while Super Kamiokande operates in Japan. However, KM3NeT uses seawater and focuses on the southern sky.
Two detectors with different missions
KM3NeT includes two separate installations. Each serves a different scientific purpose.
ARCA lies off the coast of Sicily. It tracks high-energy neutrinos from distant cosmic sources. Meanwhile, ORCA operates near southern France. It studies how neutrinos change type and what that reveals about their mass.
More than one thousand sensor modules are already in place. By 2027, scientists plan to deploy about six thousand. Step by step, the telescope is growing into one of the largest physics instruments ever built.
A neutrino unlike any other
On 13 February 2023, KM3NeT recorded an extraordinary signal. The event, named KM3 230213A, carried an energy of 220 petaelectronvolts. That level was far beyond anything seen before.
The discovery surprised the research team. They ran new simulations and checked the data again. Everything pointed to the same conclusion. This neutrino was real, and it was extreme.
The big question remains unanswered. Scientists do not yet know where it came from.
Searching for the source
Neutrinos can come from many places. Some form inside the Sun. Others emerge from supernovae. The most powerful ones likely come from distant galaxies with active black holes.
One leading idea points to blazars. These are galaxies where a supermassive black hole fires energy jets straight toward Earth. If confirmed, this would link neutrinos directly to the most violent engines in the Universe.
For now, the mystery continues. With every new detection, KM3NeT brings scientists closer to understanding forces that shaped the cosmos long before Earth existed.
