The origins of high-energy neutrinos have been traced back to black holes in distant quasars, according to Russian physicists.

Astrophysicists from Russia have come close to addressing the puzzle of where high-energy neutrinos originate in space. The researchers combined data from the Antarctic neutrino observatory IceCube with data from long electromagnetic waves obtained by radio telescopes. Flares in the cores of distant active galaxies, which are thought to hold supermassive black holes, were shown to be connected to cosmic neutrinos. As matter approaches the black hole, part of it is accelerated and expelled into space, giving rise to neutrinos, which travel at almost the speed of light through the cosmos.

The research was published in the Astrophysical Journal and is also available on the arXiv preprint server.

Neutrinos are enigmatic particles whose mass is unknown even to scientists. They can move through objects, people, and even entire planets with ease. When protons accelerate to almost the speed of light, high-energy neutrinos are produced.

The Russian physicists were interested in the origins of ultra-high-energy neutrinos, which have an energy of 200 trillion electron volts or more. The readings of the IceCube facility, which is buried under Antarctic ice, were compared to a huge number of radio observations by the researchers. The elusive particles were discovered in the cores of quasars during radio frequency flares.

Some galaxies have quasars, which are sources of radiation. They are dominated by a giant black hole that eats stuff in a disk surrounding it and ejects incredibly strong jets of ultrahot gas.

“High-energy neutrinos are created in active galactic nuclei, according to our observations, especially during radio flares. Because both neutrinos and radio waves move at the speed of light, they arrive at the Earth at the same time “Alexander Plavin, the study’s first author, stated.


Plavin is a PhD student at the Russian Academy of Sciences’ Lebedev Physical Institute and the Moscow Institute of Physics and Technology. As a consequence, he is one of the few young researchers to achieve such high-quality discoveries so early in their scientific careers.

Neutrinos appear from unexpected places

The scientists discovered that the neutrino events observed by IceCube came from brilliant quasars identified by a network of radio telescopes across the world after examining roughly 50 of them. The network employs very long baseline interferometry, the most precise means of viewing distant objects in the radio band. This technology allows for the “assembly” of a massive telescope by scattering several antennas over the world. The Max Planck Society’s 100-meter telescope at Effelsberg is one of the network’s major components.

The neutrinos may have also appeared during radio flares, according to the researchers. The scientists used data from the Russian RATAN-600 radio telescope in the North Caucasus to test their hypothesis. Despite the widely held belief that high-energy neutrinos are produced in tandem with gamma rays, the theory proved to be extremely probable.

“Previous study on the origins of high-energy neutrinos had looked for their source directly ‘in the limelight.’ We thought we’d try out a novel concept with minimal chance of success. But we struck it rich!” Yuri Kovalev of the Lebedev Institute, the Max Planck Institute for Radio Astronomy, and the Max Planck Institute for Radio Astronomy remarked. “That highly exciting conclusion was made possible by data from years of observations on worldwide radio telescope arrays, and the radio band proved out to be key in nailing down neutrino sources.”

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“At first, the results appeared to be ‘too good to be true,’ but after carefully reanalyzing the data, we established that the neutrino occurrences were obviously related with the signals picked up by radio telescopes,” stated Sergey Troitsky of the Russian Academy of Sciences. “Based on data from years of observations by the RAS Special Astrophysical Observatory’s RATAN telescope, we found that the chance of the results being random is barely 0.2 percent. This is a huge step forward for neutrino astronomy, and our discovery now necessitates theoretical answers.”

Using data from Baikal-GVD, an underwater neutrino detector in Lake Baikal that is in the last stages of development and is already partially operational, the team plans to double-check the findings and figure out the process underlying the neutrino origins in quasars. The so-called Cherenkov detectors used to detect neutrinos, such as IceCube and Baikal-GVD, rely on a huge amount of water or ice to maximize the number of neutrino occurrences while also preventing the sensors from firing accidentally. Continuing to observe distant galaxies with radio telescopes is, of course, critical to this endeavor.

As an instance:

The Russian Academy of Sciences’ Institute for Nuclear Research, which was founded in 1970, is a center for experimental, observational, and theoretical research in high-energy, nuclear, cosmic ray, neutrino, and particle physics, as well as accelerator engineering and cosmology. The Baksan Neutrino Observatory in Kabardino-Balkaria, Russia, as well as a high-current linear hydrogen ion accelerator in Moscow and the Baikal Deep Underwater Neutrino Telescope in Irkutsk Oblast, Russia, are part of the INR RAS.

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The Russian Academy of Sciences’ Special Astrophysical Observatory, founded in 1966, is a research institution dedicated to the physics and evolution of extragalactic objects, stars, the interstellar medium, and solar system objects. The 6-meter BTA optical telescope and the RATAN-600 radio telescope, both located in Karachay-Cherkessia, Russia, are operated by SAO RAS.

The Moscow Institute of Physics and Technology, which was founded in 1946, is a major Russian university that ranks among the greatest higher education institutions in the world. MIPT offers degrees in physics, mathematics, informatics and computer engineering, chemistry, biology, and other natural and engineering disciplines. With 64 new labs run by globally famous academics created in recent years, the Institute doubles as an advanced research hub. Yuri Kovalev, a corresponding RAS member, leads the Laboratory of Fundamental and Applied Research of Relativistic Objects of the Universe, which studies quasar jets, the structure of pulsar magnetospheres, accretion discs, and young star jets, as well as binary black holes and other dense binary systems.

The Max Planck Institute for Radio Astronomy (MPIfR) is a research institution in Bonn that conducts astronomical investigations across the electromagnetic spectrum with a concentration on radio astronomy and theoretical astrophysics. It was founded in 1966. Radio astronomy studies stellar evolution, young stellar objects, stars in late stages of evolution, pulsars, the interstellar medium of the Milky Way and other galaxies, magnetic fields in the universe, radio galaxies, quasars, and other active galaxies, dust and gas at cosmological distances, cosmic rays, and high-energy particle physics to learn more about the physics of stars, galaxies, and the universe.



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