The origin of high-energy neutrinos detected

Where neutrinos come from?

Neutrinos are strange particles so tiny that scientists don’t have the foggiest idea about their mass. They pass easily through objects, people, and even whole planets. High-energy neutrinos are made when protons accelerate to almost the speed of light.

In a new study, a team of Russian astrophysicists is on the verge of tackling the riddle of where high-energy neutrinos originate from in space. The team analyzed the information on the elusive particles gathered by the Antarctic neutrino observatory IceCube and on long electromagnetic waves estimated by radio telescopes. 

Cosmic neutrinos ended up being connected to flares at the centers of distant active galaxies, which are accepted to have supermassive black holes. As matter falls toward the black hole, some of it is quickened and launched out into space, offering to ascend to neutrinos that at that point coast along through the universe at about the speed of light.

The team mainly focused on the origins of ultra-high-energy neutrinos, at 200 trillion electron volts, or more. They compared the estimations of the IceCube office, covered in the Antarctic ice, with a large number of radio observations. The elusive particles were found to rise during radiofrequency flares at the centers of quasars.

The study’s first author Alexander Plavin said, “Our findings indicate that high-energy neutrinos are born in active galactic nuclei, particularly during radio flares. Since both the neutrinos and the radio waves travel at the speed of light, they reach the Earth simultaneously.”

Scientists analyzed almost 50 neutrino events detected by IceCube. They showed that these particles originated from bright quasars detected by a network of radio telescopes around the planet. 

The network uses the most precise method of observing distant objects in the radio band: very long baseline interferometry. This method enables “assembling” a giant telescope by placing many antennas across the globe. Among the most abundant elements of this network is the 100-meter telescope of the Max Planck Society in Effelsberg.

What’s more, the team also theorized that the neutrinos emerged during radio flares. To test this idea, they examined data from the Russian RATAN-600 radio telescope in the North Caucasus. The hypothesis the Russian RATAN-600 radio telescope in the North Caucasus. 

Yuri Kovalev from Lebedev Institute, MIPT, and the Max Planck Institute for Radio Astronomy commented said, “Previous research on high-energy neutrino origins had sought their source right ‘under the spotlight.’ We thought we would test an unconventional idea, with little hope of success. But we got lucky!”

“The data from years of observations on international radio telescope arrays enabled that fascinating finding, and the radio band turned out to be crucial in pinning down neutrino origins.”

Sergey Troitsky from the Institute for Nuclear Research of RAS added, “At first the results seemed ‘too good’ to be reliable, but after carefully reanalyzing the data, we confirmed that the neutrino events were associated with the signals picked up by radio telescopes. We checked that association based on the data of yearslong observations of the RATAN telescope of the RAS Special Astrophysical Observatory, and the probability of the results being random is only 0.2%. This is quite a success for neutrino astrophysics, and our discovery now calls for theoretical explanations.”

However, scientists want to recheck their findings and discover the mechanism behind the neutrino origins in quasars using the data from Baikal-GVD, an underwater neutrino detector in Lake Baikal, which is in the final stages of construction and already partly operational. 

The so-called Cherenkov sensors, used to spot neutrinos — including IceCube and Baikal-GVD — rely on a large mass of water or ice as a means of both maximizing the number of neutrino events and preventing the sensors from accidental firing. Of course, continued observations of distant galaxies with radio telescopes are equally crucial to this task.

Journal Reference:
  1. Alexander Plavin, Observational Evidence for the Origin of High-energy Neutrinos in Parsec-scale Nuclei of Radio-bright Active Galaxies. DOI: 10.3847/1538-4357/ab86bd

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