New record neutrino: Scientists puzzle over cosmic sources!

New record neutrino: Scientists puzzle over cosmic sources!

The IceCube neutrino detector, which is located at the South Pole and extends up to 2.5 kilometers deep into the ice, has been in use since 2009 to research the sources of cosmic rays. Scientists, including researchers from the Ruhr University Bochum, face the challenge that most of the neutrinos detected come from the Earth's atmosphere. This fact makes it difficult to clearly identify the cosmic sources. Neutrinos are known as “ghost particles” because they pass through matter without interacting with it. But IceCube recently made a significant advance: An extremely high-energy cosmic neutrino was detected with an energy of 220 petaelectron volts, which is 22 quadrillion times the energy of an electron. This discovery was captured by the Kilometer Cube Neutrino Telescope (KM3NeT) in the Mediterranean Sea and represents a new record in neutrino astronomy, after IceCube previously detected neutrinos at 6.5 petaelectronvolts and 10 petaelectronvolts.

Researchers continue to work intensively to determine the origin of these neutrinos. The origin of the recently detected neutrino and the process of its generation are currently unclear, possible sources could be active supermassive black holes or supernova explosions. Charged particles, such as protons, are deflected by magnetic fields, making it difficult to trace their origin. Prof. Dr. Anna Franckowiak, who leads the Multi-Wavelength and Multi-Messenger Astronomy Working Group, hopes to discover a supernova in the Milky Way that could produce large numbers of neutrinos.

Improving detection methods

To improve the detection and analysis of neutrinos, the IceCube team is developing new technologies. As part of the Gen2 preliminary phase of the IceCube upgrade, which is scheduled to be completed by 2024, intelligent readout systems for data transmission as well as new, more powerful optical sensors are being developed. These sensors can collect almost three times as much light as current models. The use of 24-pixel sensors instead of single-pixel sensors and wavelength shifters to improve light transmission are further advances expected.

Machine learning methods are also used to classify neutrino events more efficiently. These technologies enable accelerated filtering of relevant data from the measurements, enabling the team to make even weak signals more visible. In 2023, the Milky Way's neutrino signal was made visible, which is a significant step in research.

The challenge of cosmic rays

Despite its successes, IceCube has not discovered a neutrino source of the required significance in the past. A source is only considered proven if the probability of a cosmic origin is 1:1.7 million (5 sigma). So far, a neutrino with a probability of 3 sigma was assigned to a blazar, other neutrinos detected in 2022 and 2023 had probabilities of 3.2 sigma and 4.2 sigma, respectively, which were associated with an active galactic nucleus. Nevertheless, the search for the origin of these particles remains a central challenge.

The combination of the results from various research projects, such as the aforementioned collaboration with the KM3NeT and the improved detection methods, could shed light on the mysterious behavior of cosmic rays in the future. The researchers are confident that further developments in the IceCube experiment will make a significant contribution to our understanding of the universe.