For the first time, researchers have produced a neutrino image of the Milky Way, which was observed with the IceCube telescope in the Antarctic ice.
The neutrino image of the Milky Way suggests that cosmic ray interactions are more intense in the centre of our galaxy than previously thought.
The paper, ‘Observation of High-Energy Neutrinos from the Galactic Plane,’ is published in the journal Science.
Observing our galaxy with neutrinos
For centuries, the view of our galaxy has inspired awe – visible with the naked eye as a hazy band of stars that stretches across the sky.
Now, researchers at the IceCube telescope have produced a neutrino image of the Milky Way.
Neutrinos are tiny, ghostlike particles that fly freely through matter and space.
These particles were detected with the IceCube Neutrino observatory – a neutrino telescope built at the South Pole and monitoring 1 billion tons of the Antarctic ice for the rare neutrino interactions.
“Seeing our galaxy with neutrinos is something that we dreamed of, but which seemed out of reach for our project for many years to come,” said Chad Finley, associate professor at Stockholm University and one of the IceCube team members who worked closely on the paper.
“What made this result possible today is the revolution in Machine Learning, allowing us to explore much deeper into our data than before.”
Removing uncertainties about the intensity of cosmic ray interactions
Over the last century, astronomers began to study the Milky Way in all wavelengths of light.
Researchers believe that high-energy gamma rays in our galaxy are created by the interaction of cosmic rays, high-energy protons, and nuclei, with galactic gas and dust. This process is thought to also produce neutrinos.
However, large uncertainties about the intensity of cosmic ray interactions in parts of the Milky Way made predictions for neutrinos a challenge.
The analysis method used to produce the neutrino image of the Milky Way was originally developed in 2017 at Stockholm University by Jonathan Dumm, a postdoctoral researcher at the Oskar Klein Centre.
“Jon realised that if the upper range of these neutrino predictions were correct, they might have been faintly detectable in the IceCube data we had at the time,” stated Finley.
More years of data-taking are required
To get a clearer neutrino image of the Milky Way, however, the researchers believe that more years of data-taking are needed.
While the IceCube Observatory records billions of events each year, only a tiny fraction is due to neutrinos from space. This is because identifying these neutrino events is a difficult computational task.
Thanks to the development of new computing techniques called Deep Neural Networks, it is now possible to identify these neutrino events with 20 times higher efficiency.
“High-energy neutrinos provide us with a wonderful new tool for studying the Milky Way. The next step is to identify the neutrino sources, potentially the sites for galactic cosmic ray acceleration,” said Olga Botner, senior professor at Uppsala University.
“If realised, the planned IceCube-Gen2 would enable a deeper yet exploration of the galactic plane, allowing us to distinguish between various source distributions and models for cosmic ray propagation.”
