Discovery of extragalactic neutrino factories

(ORDO NEWS) — High-energy and hard to detect, neutrinos travel billions of light-years through space before reaching our planet.

Although it is known that these elementary particles are born somewhere deep in the Universe, far from us, their exact origin is still unknown.

In a new study, an international team sheds light on one aspect of this mystery – that neutrinos can be formed by blazars, the nuclei of galaxies containing supermassive black holes (SMBHs).

The Earth’s atmosphere is constantly bombarded by cosmic rays. These beams consist of electrically charged particles with energies up to 10^20 electron volts.

This is a million times the maximum energy achieved in the most powerful particle accelerator on Earth, the Large Hadron Collider, located near Geneva.

These extremely high-energy particles come to us from deep space, where they have previously traveled distances of billions of light years.

But where are cosmic rays born and get these gigantic speeds with which they then pass through the entire Universe? These questions have haunted astrophysicists for more than a hundred years.

Where cosmic rays are born, neutrinos are also formed. Neutrinos are neutral particles that are difficult to detect. They have almost no mass and weakly interact with matter.

They rush through the universe, passing unhindered through galaxies, planets and even the human body. “Astrophysical neutrinos are formed exclusively by processes involving the acceleration of cosmic rays,” said astrophysics professor Sara Buson of the University of W├╝rzburg.

Julius and Maximilian, Germany. That is why neutrinos are a unique signal that allows us to trace the origin of cosmic rays in the Universe.

Despite the large amount of data collected by astrophysicists, the relationship between high-energy neutrinos and the astrophysical sources that give rise to them has not been firmly established over the years.

Sara Buson has always considered this a big challenge for herself. In 2017, she and her colleagues presented the first compelling evidence in an article for the journal Science that a blazar called TXS 0506+056 could be a source of neutrinos.

Blazars are active galactic nuclei containing SMBHs that can emit more light than the entire host galaxy combined. The article caused a great resonance in the astrophysical community.

Following this first, inspiring step, in June 2021 Prof. Buson’s group launched an ambitious multi-channel research project with the support of the European Research Council.

It includes the analysis of various types of space signals (including the neutrino signal). The main goal is to elucidate the origin of astrophysical neutrinos.

The new study presents the first success of this project, with Sarah Buson and her team demonstrating, using numerical simulations, a robust relationship between blazars and astrophysical neutrino sources.

In their work, the team used a neutrino detector called the IceCube Neutrino Observatory, located in Antarctica, as well as the BZCat catalog, one of the most detailed catalogs of blazars to date.

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