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November 9, 2022 priority outreach

Icecube Neutrinos Give First Glimpse Into the Inner Depths of an Active Galaxy

Icecube Neutrinos Give First Glimpse Into the Inner Depths of an Active Galaxy

UNIVERSITY PARK, Pa. — For the first time, an international team including Penn State scientists has found evidence of high-energy neutrino emission from Messier 77, also known as NGC 1068, an active galaxy in the constellation of Cetus.

Neutrinos are fundamental particles with no charge and almost no mass, and they rarely interact with other matter. High-energy neutrinos — like those detected here with energies in the teraelectron volt (TeV), or trillion-electron volt, range — can travel for billions of light-years through space without being deflected or absorbed. Thus, while they are extremely difficult to detect, they can provide accurate information about the distant universe, especially when the information the carry can be combined with information from other cosmic signals in what is called “multimessenger” astronomy.

The detection was made by the IceCube Neutrino Observatory, a massive neutrino telescope encompassing one billion tons of instrumented ice at depths from 1.5 to 2.5 kilometers below Antarctica's surface near the South Pole.

"IceCube is a veritable discovery machine,” said Doug Cowen, professor of physics and of astronomy and astrophysics at Penn State and a long-time IceCube collaborator. “The huge detector has lived up to its promise to launch the brand-new field of high energy neutrino astronomy, and then some, now by giving us glimpses behind a black hole's black-out curtain of matter. IceCube has once again proved that when humanity points a new instrument at the heavens — starting with Galilleo's first telescope — our knowledge of the universe around us increases by leaps and bounds."

This unique telescope, which explores the farthest reaches of our universe using weakly interacting neutrinos instead of light, recorded the first observation of a potential source of high-energy astrophysical neutrinos in 2017. The source of these first observations is the known blazar TXS 0506+056, which is situated in the night sky just off the left shoulder of the constellation Orion and about 4 billion light-years from Earth.

Blazars are very luminous and distant active galaxies with a powerful, relativistic jet of particles pointing directly at us. Unlike NGC 1068, the blazar TXS 0506+056 had not been studied much before the multimessenger detection of neutrinos and high-energy electromagnetic radiation that allowed follow-up measurements by almost 20 telescopes around the world. Now, the observation of neutrino emission from a different type of active galaxy brings us closer to understanding the supermassive black holes powering them.

“One neutrino can single out a source. But only an observation with multiple neutrinos will reveal the obscured core of the most energetic cosmic objects,” said Francis Halzen, a professor of physics at the University of Wisconsin–Madison, the headquarters of the National Science Foundation (NSF)´s Antarctic neutrino facility, and principal investigator of IceCube. “IceCube has accumulated some 80 neutrinos of TeV energy from NGC 1068, which are not yet enough to answer all our questions, but they definitely are the next big step towards the realization of neutrino astronomy.”

The results appear Nov. 4 in the journal Science.

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About our wordmark
Monica Rincon Ramirez

The IGC wordmark was created by Monica Rincon Ramirez while she was a graduate student at the Institute. Monica enjoys drawing new connections between fundamental theory and observations. Her graduate work included general relativity, loop quantum gravity, and quantum fields in cosmological backgrounds; her thesis focused on effective quantum corrections to gravitational phenomena from spinfoams and applications to cosmology. She received her PhD in 2024.

The wordmark symbolizes the scope of research at the IGC. The base represents quantum gravity, evoking the quantum geometrical picture from spinfoams and loop quantum gravity — approaches studied at the Center for Fundamental Theory. The middle shows galaxies embedded in a smooth surface characteristic of spacetime in general relativity and the larger physical scales studied at the Center for Theoretical and Observational Cosmology. The top curves to an extreme representing a supermassive black hole accompanied by an energetic jet, with a binary black hole pair nearby — the high-energy phenomena studied at the Center for Multimessenger Astrophysics.