In November 2022, the IceCube collaboration published a result in Science that may turn out to be even more consequential than their famous 2017 detection of TXS 0506+056. The new result identified a specific galaxy as a steady source of high-energy cosmic neutrinos — the first time a non-transient point source had been pinned down.
The galaxy is NGC 1068, also known as Messier 77. It is a Seyfert galaxy about 47 million light-years away in the constellation Cetus, easily visible in amateur telescopes and well-known for being one of the closest active galactic nuclei to Earth. After analyzing ten years of accumulated IceCube data, the team found an excess of high-energy neutrino events coming from NGC 1068’s direction at a statistical significance of 4.2σ — strong enough to be identified as a real source, though just below the formal 5σ discovery threshold.
NGC 1068, in other words, is the second confirmed extragalactic point source of cosmic neutrinos, and the first one to emit them steadily rather than in transient flares.
How NGC 1068 differs from TXS 0506+056
The two confirmed cosmic neutrino sources illustrate two different kinds of active galactic nucleus.
TXS 0506+056 is a blazar: an active galactic nucleus whose relativistic jet points almost directly at Earth. We see it through the throat of the jet. The relativistic Doppler boost makes it bright at very high energies, but the emission is highly variable — flaring up and quieting down on timescales of days to months. The 2017 neutrino detection coincided with one such flare.
NGC 1068 is a Seyfert galaxy of type 2 — a different kind of active galactic nucleus whose central engine is obscured behind a dense dust torus. We do not see the jet straight on; we see the galaxy roughly face-on with the central black hole hidden behind a wall of gas and dust. The accretion onto the black hole still produces enormous luminosity, but it leaks out in different patterns than a blazar’s.
The neutrino signal IceCube detected from NGC 1068 is consistent with a steady, continuous emission rather than a flare. That makes it the first confirmed steady-state extragalactic neutrino source.
Why steady-state matters
Cosmic-ray and neutrino astronomy has long faced a puzzle. IceCube’s measured diffuse astrophysical neutrino flux — the total rate of cosmic neutrinos integrated over the sky — is much larger than can be accounted for by the handful of flaring blazars known to produce neutrinos. There must be other sources. The question has always been: what kind?
A steady-state source like NGC 1068 is significant because it suggests that obscured AGN of the Seyfert type could collectively contribute substantially to the diffuse flux. These galaxies are far more numerous than blazars (because a blazar requires the jet to point in our specific direction, while a Seyfert is visible from many angles), and they exist throughout the universe.
If NGC 1068 turns out to be a representative example of a large class of similar emitters, then the diffuse neutrino flux IceCube has been seeing since 2013 may have its dominant origin in Seyfert galaxies rather than blazars or other exotic sources. This would be a major shift in how the field thinks about cosmic-ray and neutrino origins.
How IceCube actually found it
The challenge of identifying point sources in IceCube data is that most events have angular resolutions of a few degrees, which is much wider than the apparent size of individual galaxies. A single neutrino event cannot, by itself, be assigned to a specific source. Identification requires statistical accumulation.
The team applied a refined directional analysis — incorporating machine-learning techniques to improve angular resolution — to ten years of IceCube data. They tested each of about 110 catalogued candidate sources, including known active galaxies, magnetars, and other plausible high-energy objects.
For NGC 1068, they found an excess of about 79 cosmic neutrino events above background at the position of the galaxy. The neutrino energies were typical for IceCube’s astrophysical sample — a few TeV up to perhaps 15 TeV.
The 4.2σ significance is unusual for a discovery announcement in particle physics, where 5σ is the conventional threshold. The collaboration was careful to frame the result as strong evidence rather than discovery — but the result is widely accepted in the community, and additional data are expected to push it past 5σ within a few years.
What it tells us about the central engine
NGC 1068 has been studied at every wavelength of the electromagnetic spectrum for decades. The picture that emerges is that the central engine — the inner few light-years around the supermassive black hole — is wrapped in a dense torus of gas and dust. The torus is essentially opaque to high-energy gamma rays, which means that gamma-ray observations underrepresent what is happening at the core.
Neutrinos, by contrast, escape easily even through dense material. So they offer a unique view of the obscured center.
The NGC 1068 neutrino signal implies that cosmic-ray protons are being accelerated somewhere in the central engine, then colliding with the dense ambient material, producing pions whose decays give the observed neutrinos. The same collisions should also produce gamma rays — but those gamma rays would be absorbed by the surrounding gas and never reach Earth.
In other words: the neutrinos confirm a hadronic acceleration process that the electromagnetic observations could not directly see. This is a textbook example of why multi-messenger astronomy is valuable. Different probes reveal different layers of the same source.
A new class of source
The discovery of NGC 1068 as a neutrino source has triggered active follow-up across the field. Several other Seyfert galaxies in the IceCube data have now been highlighted as plausible additional sources, though none yet at the 4σ level achieved for NGC 1068.
Theoretical models of how cosmic rays are accelerated in obscured AGN have been refined. The most promising models invoke acceleration in the inner corona of the accretion flow — the hot ionized region very close to the central black hole — followed by photo-hadronic interactions with the dense surrounding ultraviolet and X-ray photon field. The exact mechanism is still being debated, but the basic picture seems to hold up.
Multi-messenger campaigns
Like TXS 0506+056 before it, NGC 1068 is now a target for multi-messenger observation campaigns. X-ray telescopes including NuSTAR and XMM-Newton, gamma-ray observatories including Fermi-LAT, optical surveys, and radio interferometers all contribute different pieces of the picture. The combination of data is gradually refining the model of the central engine.
Future observatories will help further. IceCube-Gen2, the planned expansion of the existing detector at the South Pole, will offer roughly an order of magnitude more sensitivity. KM3NeT in the Mediterranean will provide a complementary view of the southern sky with different systematics. Baikal-GVD in Lake Baikal adds yet another vantage point. Together, the next decade should bring NGC 1068’s significance well past 5σ and reveal whether other Seyfert galaxies emit at comparable levels.
The picture of cosmic-ray origins, finally
For more than a century — since Victor Hess’s 1912 balloon flights discovered cosmic rays — the question of where the universe’s most energetic particles come from has resisted complete answer. We know cosmic rays exist. We know some are accelerated within our galaxy (probably by supernova remnants), but the highest-energy ones must come from outside.
NGC 1068’s identification as a steady neutrino source is one of the most concrete steps toward answering that question. Active galactic nuclei — and specifically, the obscured Seyfert variety — appear to be accelerating protons to very high energies, producing both the neutrinos IceCube detects and the cosmic rays that fill intergalactic space.
The picture is not yet complete. NGC 1068 is one source. Many more — known and unknown — remain to be identified. But for the first time, the structure of cosmic-ray and neutrino origins is starting to come into focus, and it is being revealed by IceCube’s patient accumulation of high-energy events from a galaxy 47 million light-years away.
For the first identified cosmic neutrino source, see TXS 0506+056. For the broader IceCube context, see Inside IceCube and Cosmic messengers from blazars. For our own galaxy’s neutrino emission, see The Milky Way’s neutrino glow.
Further reading
Primary sources
- IceCube collaboration, “Evidence for neutrino emission from the nearby active galaxy NGC 1068”, Science 378:538 (2022) — the identification paper
- IceCube official NGC 1068 announcement
Background and context
- Wikipedia: NGC 1068 — host galaxy, also known as Messier 77
- NASA — NGC 1068 observations across the spectrum — Hubble’s optical imagery
- Quanta Magazine — “A galactic mystery is solved by a galaxy’s neutrinos” — search “NGC 1068” for feature coverage
Frequently asked
What is NGC 1068?
NGC 1068 (also called Messier 77) is a Seyfert galaxy about 47 million light-years from Earth in the constellation Cetus. Like all Seyfert galaxies, its core contains a supermassive black hole that is actively pulling in surrounding gas, producing intense radiation across the electromagnetic spectrum. It is one of the closest and best-studied active galactic nuclei in the sky.
How did IceCube identify NGC 1068 as a neutrino source?
By performing a directional search through ten years of accumulated IceCube data, looking for an excess of high-energy neutrino events from the direction of cataloged candidate sources. NGC 1068 produced an excess of about 79 high-energy neutrinos above background, at a statistical significance of 4.2σ — strong enough to identify it as a real source, though just below the 5σ discovery threshold.
How does NGC 1068 differ from TXS 0506+056?
Both are active galactic nuclei, but they differ structurally. TXS 0506+056 is a blazar — its relativistic jet points at Earth, and its neutrino signal is concentrated in flares. NGC 1068 is a Seyfert galaxy whose jet does not point at Earth, and its neutrino signal is a steady glow rather than a flare. NGC 1068 is also much closer (47 million light-years versus 4 billion) and emits about ten times more neutrinos per unit time as seen from Earth.
Why does the NGC 1068 result matter?
It establishes that obscured active galactic nuclei — galaxies with dense gas hiding their inner engines — can be efficient particle accelerators. It also suggests that many of the unidentified cosmic neutrinos IceCube has been seeing for years may come from a large population of Seyfert-type galaxies rather than from the rarer blazars.
What does this tell us about cosmic-ray origins?
Cosmic rays at very high energies must come from extragalactic sources, but their charged trajectories are deflected by magnetic fields so they cannot be traced back. Neutrinos travel in straight lines and can be traced. Identifying NGC 1068 as a neutrino source means it must also be accelerating cosmic rays to PeV energies — providing direct evidence about where the universe's most energetic particles are produced.
Cite this article 5 formats
APA
Neutrino Times Editorial Team. (2025, October 13). NGC 1068: the second cosmic neutrino source, and the first steady one. Neutrino Times. https://neutrino-times.com/articles/ngc-1068-seyfert-galaxy-steady-neutrino-source/
Chicago
Neutrino Times Editorial Team. "NGC 1068: the second cosmic neutrino source, and the first steady one." Neutrino Times, October 13, 2025. https://neutrino-times.com/articles/ngc-1068-seyfert-galaxy-steady-neutrino-source/.
MLA
Neutrino Times Editorial Team. "NGC 1068: the second cosmic neutrino source, and the first steady one." Neutrino Times, 13 Oct. 2025, https://neutrino-times.com/articles/ngc-1068-seyfert-galaxy-steady-neutrino-source/.
BibTeX
@misc{neutrino-times-ngc-1068-seyfert-galaxy-steady-neutrino-source,
author = {Neutrino Times Editorial Team},
title = {NGC 1068: the second cosmic neutrino source, and the first steady one},
howpublished = {Neutrino Times},
year = {2025},
month = {oct},
url = {https://neutrino-times.com/articles/ngc-1068-seyfert-galaxy-steady-neutrino-source/},
note = {Accessed: 2025-10-13}
} RIS
TY - GEN TI - NGC 1068: the second cosmic neutrino source, and the first steady one AU - Neutrino Times Editorial Team PY - 2025 DA - 2025-10-13 PB - Neutrino Times UR - https://neutrino-times.com/articles/ngc-1068-seyfert-galaxy-steady-neutrino-source/ ER -