Neutrino telescopes detect elusive particles for cosmic insights

Neutrinos are tiny, almost ghostly particles that travel through the Earth without being noticed. They are very common in the universe, but detecting them is a major challenge. Neutrinos were first proposed in the 1930s as a way to explain missing energy in nuclear reactions. Initially, scientists thought neutrinos had no mass. Now, they understand that they do have a tiny amount of mass. Neutrinos are produced in massive quantities by events like nuclear reactions in the Sun and supernova explosions. Despite their abundance, they rarely interact with other matter, making them difficult to observe. To detect neutrinos, astronomers use special telescopes that rely on the weak nuclear force, the only force with which neutrinos interact. When a neutrino collides with an atomic nucleus, it can create a muon, a heavier, charged particle. This muon travels quickly and produces a bluish light known as Cherenkov radiation. By placing light detectors in water or ice, researchers can detect this light and gather information about the initial neutrino. Two of the most well-known neutrino observatories are Super-Kamiokande in Japan and IceCube in Antarctica. Super-Kamiokande is located deep underground and contains ultra-pure water. IceCube uses the Antarctic ice sheet as its medium, with thousands of detectors embedded in the ice. There is also the European KM3NeT, currently being built under the Mediterranean Sea. Detecting neutrinos is still rare. For example, during a supernova in 1987, detectors managed to capture only 25 neutrinos, providing important insights into such explosive events. Today, IceCube regularly detects hundreds of neutrinos daily, linked to areas of star formation and black hole activity. Recently, KM3NeT detected a particularly powerful neutrino, which was 16,000 times more energetic than particles from the strongest particle colliders. The source of this neutrino remains unknown. Overall, neutrino telescopes help us explore extreme cosmic events, giving scientists a better understanding of the universe.