Physicists from the Baikal-GVD collaboration have detected galactic neutrinos with energies exceeding 200 teraelectronvolts. The sources of these neutrinos were highly likely located in the Milky Way. The paper was published in The Astrophysical Journal.
Neutrinos are currently considered one of the most difficult objects to observe: they interact virtually with matter. At the same time, cosmic neutrinos provide insight into the most extreme phenomena in the Universe—from stellar explosions to the activity of galactic nuclei. In recent years, major neutrino observatories, including IceCube in Antarctica, have reported detecting extremely high-energy neutrinos, but most of these events appear to have originated outside the Milky Way. Until now, the contribution of our galaxy to the detected astrophysical component of neutrinos remained unclear, and various theoretical estimates have diverged widely.
Researchers from the Baikal-GVD collaboration have detected high-energy neutrinos, most likely originating within our galaxy. The scientists used the Baikal-GVD neutrino telescope—a large-scale system of optical modules suspended on vertical cables in the clear waters of Lake Baikal. Each module contains a photodetector for recording Cherenkov radiation, which occurs when high-energy particles pass through the water. Using this detector, physicists track flashes of light in the water and, using this data, reconstruct the direction and energy of the neutrinos.
Scientists analyzed events with reconstructed energies above 200 teraelectronvolts, recorded during the telescope's six-year operation. Physicists observed a total of eight such events. They noted that the average deviation angle of these events from the galactic equator was significantly smaller than expected from a uniform distribution across the sky. The probability of a random coincidence was estimated at 1.4×10-2. The authors also compared the Baikal-GVD results with newly released IceCube data and found a similar pattern in both cases. When analyzing all neutrino events together, the error probability dropped to 3.4×10-4.
According to the physicists, this result suggests that the galactic contribution to the high-energy neutrino flux may be more significant than previously thought. A more detailed study, in particular a search for point neutrino sources in star-forming regions, will require larger data sets and continued observations. Baikal-GVD continues to expand its detector capacity and will be able to provide even more convincing data in the coming years.
Previously, another similar Cherenkov detector, KM3NeT, observed ultra-high-energy neutrinos (several tens of petaelectronvolts). Read about this in our article "Didn't Expect This?"
