High-energy neutrinos discovered in the Milky Way for the first time

Neutrinos play an important role in nuclear physics, for example in nuclear fusion inside the Sun. But the neutrinos IceCube is looking for are millions to billions of times more energetic and are produced in stellar explosions and in the vicinity of supermassive black holes in distant galaxies. But also in our Milky Way, the interaction of cosmic rays with gas and dust should produce high-energy neutrinos, along with gamma rays. But while this gamma radiation can be detected by satellite observatories, the search for galactic neutrinos has so far been unsuccessful.

The problem: cosmic radiation also produces neutrinos in Earth’s atmosphere and this noise is superimposed on the desired signal from the Milky Way. However, by improving their methods, the IceCube researchers have now succeeded in making neutrinos from the Milky Way visible. On the one hand, scientists have filtered out events that come from the southern sky and thus from the direction of the center of the Milky Way. To determine the exact origin of the recorded neutrinos, a machine learning-based method developed primarily at TU Dortmund was used. “These improved methods mean that we have been able to use about ten times more neutrinos for evaluation than before, and with better directional accuracy,” explained Mirco Hünnefeld of TU Dortmund. “Overall, our analysis was three times more sensitive than previous research methods.”

For the first time, IceCube data evaluated in this way provides a picture of the Milky Way as it would appear with neutrino eyes. “This image confirms what we know so far about the Milky Way and cosmic rays,” IceCube researcher Steve Sclafani said. But this is just the beginning. IceCube continues to collect data and methods need further improvement. “This is how we get an image with better and better resolution,” explains Denise Caldwell of the IceCube Project. In this way, scientists want to know exactly where neutrinos originate from. “Of course, we also hope to discover previously unknown and never-before-seen structures in our Milky Way.” (dpa/dam)