The neutrino observatory KM3Net is located in the depths of the Mediterranean Sea and measures a cosmic neutrino at the highest energies to date. It is the most energetic neutrino ever observed. This discovery proofs that neutrinos with such extreme energies are produced in the universe. Supermassive black holes in the depths of the universe could be a source of extremely fast and extremely high-energy cosmic particles. An assembly of digital optical modules which later become a part of the KM3Net neutrino telescope in the Mediterranean Sea.
On February 13, , an international collaboration, including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, measured a neutrino at record energies in the data from the kilometer-sized neutrino telescope KM3NeT.
The almost horizontally reconstructed track of the particle is shown as a line from left to right. Neutrinos are among the most mysterious elementary particles - they have no electric charge and almost no mass. Since neutrinos interact only weakly with matter, the KM3NeT telescope uses seawater as a detector volume - soon it will be several cubic kilometers. If a cosmic neutrino reacts with the atomic nuclei of the seawater, muons can be produced.
Muons are heavier than electrons but also carry a simple negative charge. The muon acquires so much kinetic energy in this reaction that it produces a cone of light as it plows through the seawater. This Cherenkov light is comparable to the sonic boom that a jet produces when flying at high speed through the atmosphere.
The neutrino telescope consists of parallel strings, each with 18 optical modules attached to them like pearls on a necklace. Each module contains 31 photomultipliers that capture and amplify weak light from all directions — including the light generated after a chain of reactions triggered by a cosmic neutrino. KM3NeT is now detecting neutrinos from extreme astrophysical events, exploring previously uncharted energy ranges.
