Active galaxies are sources of high-energy cosmic neutrinos

(ORDO NEWS) — Cosmic neutrinos are not only difficult to “catch”, but also to trace their source – until recently, this was done only once.

But researchers from the IceCube neutrino observatory , built at the Amundsen-Scott Antarctic Station in the US, tracked 79 of them back to their home galaxy.

The IceCube Observatory has discovered a second source of high-energy neutrinos from space.

These neutral fundamental particles are notoriously difficult to detect and even more difficult to trace their origins, yet they pervade the entire universe.

The new discovery should help better understand where and how they form.

In 2017, the IceCube team, led by Francis Halzen, a particle physics, astrophysics, and cosmology researcher at the University of Wisconsin-Madison, tracked their first definitive source of a single, high-energy cosmic neutrino: the blazar TXS 0506+056, which shoots a huge jet of energy towards the Earth.

This discovery has been made with many other telescopes, but using an updated data analysis method, the IceCube team was able to find a second neutrino source, named NGC 1068. This time without any outside help.

The researchers tracked the trajectories of 79 high-energy neutrinos to NGC 1068 (M 77), a relatively nearby galaxy 47 million light-years away from Earth.

“When we first published the data for these 10 years, NCG 1068 appeared, but we were not sure if this was a background fluctuation or if it was a real source,” comments Halzen.

“Now we know it’s not hesitation.”

The nature of cosmic neutrinos

Cosmic neutrinos are produced when a proton crashes into another particle, creating a stream of elementary particles, some of which later decay and emit neutrinos.

NGC 1068 seems like an almost ideal environment for such a complex process to take place, as it is an active galaxy, which means that its central supermassive black hole is consuming material and emitting powerful radiation.

At the same time, the center of NGC 1068 is shrouded in dense gas and dust clouds, which “envelop” the black hole and give radiation the opportunity to collide with neutrinos.

Active galaxies are sources of high energy cosmic neutrinos 2

There are far more active galaxies like NGC 1068 than blazars like TXS 0506+056, so this discovery could help explain why there are so many cosmic neutrinos in the universe.

“The scattered neutrino flux that we observe in the Universe is about 100 times greater than what we recorded from this single source NGC 1068, so there are surprises ahead of us,” Halzen added.

“If I had to bet, I would bet on this kind of object on an active galaxy.”

The researchers are currently working to further improve their analytical methods and upgrade the detector to track even more neutrinos and better understand how they form.


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