Scientists Uncover Surprising New Source of Cosmic Neutrinos

UCLA physicists have proposed a groundbreaking new explanation for mysterious high-energy particles detected from the distant Squid Galaxy, potentially revolutionizing our understanding of extreme cosmic environments. The surprising discovery, published April 18 in Physical Review Letters, solves a puzzle that has perplexed astronomers: why the galaxy NGC 1068 emits an abundance of ghostly neutrino particles while producing unexpectedly weak gamma rays—a pattern that defies conventional astrophysical models.

A Cosmic Detective Story in Antarctic Ice

Deep beneath the Antarctic ice, thousands of specialized sensors form the IceCube Neutrino Observatory—effectively creating “eyes” that can detect nearly invisible subatomic particles called neutrinos as they pass through our planet.

“We have telescopes that use light to look at stars, but many of these astrophysical systems also emit neutrinos,” explained Alexander Kusenko, professor of physics and astronomy at UCLA and a senior fellow at Kavli IPMU. “To see neutrinos, we need a different type of telescope, and that’s the telescope we have at the South Pole.”

What makes the observatory’s findings from NGC 1068 so puzzling is the mismatch between neutrino and gamma-ray signals. Typically, when astrophysicists detect high-energy neutrinos from space, they also observe correspondingly strong gamma-ray emissions.

Breaking Apart Atoms to Make Ghosts

The research team, including scientists from UCLA, the University of Osaka, and the University of Tokyo, determined that the neutrinos are likely produced through an entirely different mechanism than previously theorized.

Their explanation? Helium nuclei accelerated in the powerful jets of the galaxy’s central black hole crash into ultraviolet photons and break apart, releasing neutrons that subsequently decay into neutrinos without generating strong gamma rays.

“Hydrogen and helium are the two most common elements in space,” said first author and UCLA doctoral student Koichiro Yasuda. “But hydrogen only has a proton, and if that proton runs into photons, it will produce both neutrinos and strong gamma rays. But neutrons have an additional way of forming neutrinos that don’t produce gamma rays. So helium is the most likely origin of the neutrinos we observe from NGC 1068.”

Key Findings from the Research

The new model offers several advantages over traditional explanations:

• It accounts for why NGC 1068’s neutrino signal dramatically outshines its gamma-ray emission
• The energies of the resulting neutrinos (1-100 TeV range) match observations
• The model explains the distinct energy spectrum seen in both neutrinos and gamma rays
• It provides insight into extreme conditions surrounding supermassive black holes
• The findings suggest other similar galaxies may produce neutrinos through this mechanism

“This idea offers a new perspective beyond traditional corona models. NGC 1068 is just one of many similar galaxies in the universe, and future neutrino detections from them will help test our theory and uncover the origin of these mysterious particles,” said co-author and University of Osaka professor of astrophysics Yoshiyuki Inoue.

Why Does This Matter Beyond Astronomy?

What can the extreme environment around a distant galaxy’s supermassive black hole possibly have to do with our everyday lives? According to Kusenko, today’s seemingly esoteric discoveries often become tomorrow’s technological foundations.

Consider the humble electron, first identified over a century ago. “When J.J. Thompson received the 1906 Nobel Prize in physics for the discovery of electrons, he famously gave a toast at a dinner after the ceremony, saying that this was probably the most useless discovery in history,” said Kusenko. “And, of course, every smartphone, every electronic device today, uses the discovery that Thompson made nearly 125 years ago.”

He points to other examples where fundamental science led to transformative applications, including how particle physics research created the foundation for the World Wide Web and how nuclear magnetic resonance studies eventually produced the MRI technology now vital in modern medicine.

Looking Toward a Neutrino-Enlightened Future

The finding has potential implications closer to home. Our own Milky Way galaxy also harbors a supermassive black hole at its center with similar physical processes potentially occurring.

“We don’t know very much about the central, extreme region near the galactic center of NGC1068,” said Kusenko. “If our scenario is confirmed, it tells us something about the environment near the supermassive black hole at the center of that galaxy.”

“We stand at the very beginning of the new field of neutrino astronomy, and the mysterious neutrinos from NGC 1068 are one of the puzzles we have to solve along the way,” Kusenko added. “Investment in science is going to produce something that you may not be able to appreciate now but could produce something big decades later. It’s a long-term investment, and private companies are reluctant to invest in the kind of research we’re doing. That’s why government funding for science is so important, and that’s why universities are so important.”

As neutrino astronomy continues to evolve, this discovery may represent just the first of many insights into the hidden mechanisms powering the universe’s most energetic phenomena—potentially laying groundwork for future technologies we can scarcely imagine today.