2023-06-29 20:00:10
In places without light pollution, we can see the Milky Way like a diffuse band of stars on the horizon. The astronomical community also observes and studies it in detail at different wavelengths, but from now on it will have a new type of ‘lens’: the neutrinos.
For the first time, the neutrino observatory IceCubea gigantic one cubic kilometer detector built under the Amundsen-Scott South Pole stationhas produced an image of our galaxy using those tiny, ghostly astronomical messengers.
The IceCube detector records the first evidence of high-energy neutrino emission from the Milky Way
The members of this international collaboration, made up of more than 350 scientists, present in the journal Science proof of issuance high energy neutrinos coming from our galaxy.
“Neutrinos are subatomic particles, as are electrons. However, they are special in that they interact only through the weak force. Just as light can pass through the glass of a window without difficulty, neutrinos can pass through everything, including planet Earth, which is why they are so difficult to detect”, explains the IceCube spokesperson to SINC, Ignacio TaboadaProfessor of Physics at the Georgia Institute of Technology (USA).
These subatomic particles can pass through everything, including planet Earth, which is why they are so difficult to detect.
Ignacio Taboada (IceCube spokesperson)
“That’s why IceCube is so big, to be able to observe the few neutrinos that do interact,” he continues. And regarding the fact that they are of “high energy”, it is in comparison with other neutrinos, such as those produced by the Sun, which have energies a million times lower.”
The IceCube laboratory under a starry night sky, with the Milky Way in the background rising above low auroras. / Yuya Makino, IceCube/NSF
Taboada underlines the importance of this finding: “This is the first time that the Milky Way has been observed with something other than light: neutrinos. Visible and invisible light (radio, microwave, infrared, X-rays, gamma rays) have been used extensively to study our galaxy, but neutrinos are not light. And by studying in different ways, you learn new things.”
It is the first time that the Milky Way has been observed with something other than light: neutrinos, and by studying it in a different way, new things are learned
Ignacio Taboada
IceCube Principal Investigator, Francis HalzenProfessor of Physics at the University of Wisconsin-Madison, adds: “What is intriguing is that, unlike light of any wavelength, in the case of neutrinos, the universe eclipses nearby sources of light. our own galaxy.
The IceCube team had already detected high-energy neutrinos of extragalactic origin, such as those coming from the nearby galaxy NGC1068, and they assume that the same could happen in other more distant ones. But what happens in our Milky Way? The observations of gamma rays show bright emissions from inside the galactic plane and, since gamma rays and neutrinos are believed to be produced by the same astrophysical processes, that plane was the expected site of neutrino emission, as it has been.
Machine learning techniques
The demonstration has been carried out thanks to machine learning artificial intelligence techniques, using data recorded (about 60,000 neutrinos) over 10 years by the IceCube observatory in Antarctica. Researchers have presented the first statistically sound evidence of high-energy neutrino emission from the galactic plane, with results consistent with the expected distribution and interactions of cosmic rays within our galaxy.
View of neutrinos (blue sky map) in front of an artist’s rendering of the Milky Way. / IceCube Collaboration/Science Communication Lab for CRC 1491
“We detect neutrinos from our own galaxy by studying their direction and energy,” explains Taboada, “there is an excess of these high-energy particles that point approximately in the direction of the plane of the galaxy, and especially towards the galactic center”.
The mysterious sources of these neutrinos
But where exactly do they come from? “It is not possible to know for sure what produces these neutrinos, since we have observed the Milky Way as a whole”, replies the professor, “although there are two reasonable possibilities and probably both occur, but we don’t know which is more important”.
Neutrinos could come from point sources of cosmic rays, and these, in turn, produce more as they propagate. This is how our galaxy could shine diffusely everywhere, especially towards the center
Ignacio Taboada
On the one hand, “neutrinos can be produced by cosmic ray sources in our galaxy: a collection of point sources, like a star, of neutrinos –he clarifies–. But these cosmic rays, which have an electrical charge, propagate through the galaxy and when colliding with gas, stellar dust, etc., produce more neutrinos”.
“That would result in our galaxy shining diffusely everywhere, but more intensely towards the center,” says Taboada, who anticipates that now “the next step is to identify the specific sources within the galaxy.” That and other challenges will be addressed in the following analyzes provided by IceCube.
As neutrino astronomy evolves, we will get a new lens with which to observe the universe
Naoko Kurahashi Neilson, member of the IceCube collaboration
Another member of the collaboration, Naoko Kurahashi Neilson, Professor of Physics at Drexel University (USA), concludes: “Observing our own galaxy for the first time using particles instead of light is a big step. As neutrino astronomy evolves, we will get a new lens with which to observe the universe.”
Chronology of the main milestones in neutrino astronomy. / IceCube Collaboration
The IceCube Neutrino Observatory
In the heart of Antarctica, at the Amundsen-Scott polar base, is this observatory financed by the US National Science Foundation (NSF), with the support of the 14 countries that host institutional members of the IceCube collaboration.
This neutrino detector, about one cubic kilometer buried in ice, operates with more than 5,000 digital optical modules (DOMs) frozen at depths between 1,450 and 2,450 meters.
Schematic of the IceCube observatory. / IceCube/NSF
Reference:
The IceCube Collaboration. “Observation of high-energy neutrinos from the Galactic plane”. Science2023
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