Radio Telescopes May Help Trace the Origins of IceCube's Elusive Cosmic Neutrinos

At the South Pole, a detector buried in Antarctic ice has spent years waiting for something that almost never happens: a neutrino bumping into a water molecule. That patience has now been rewarded with a Nobel Prize for the IceCube experiment, and a physicist writing about the work is asking the next question. Where do the neutrinos IceCube catches actually come from?

Neutrinos weigh almost nothing and pass through the Earth without touching anything. They can come from bananas or from supernovas, the explosive deaths of massive stars. They skip electromagnetism, the force behind light, chemistry and electronics, and interact only through the weak interaction, which acts over distances smaller than the inside of an atomic nucleus. A neutrino has to pass extraordinarily close to the center of an atom to register at all.

Scientists have detected astrophysical neutrinos since the 1960s, mostly from the sun and, in at least one case, from a supernova. IceCube changed the scale. Over roughly the past decade it has used the densely packed South Pole ice as a telescope: given enough time, some molecules interact with a neutrino, and detectors see the radiation that follows. More time means more interactions. By this method IceCube has found astrophysical neutrinos hundreds of thousands of times more energetic than those seen before.

The same reluctance to interact makes neutrinos useful, since they can reveal high-energy processes in places light cannot escape. The difficulty is that nobody knows where most of them originate. Quasars, where black holes millions of times the mass of the sun tear matter apart, are leading candidates. In 2017, IceCube detected a neutrino that appeared to come from the quasar TXS 0506+056 just as another telescope saw that object burst with gamma rays. That fits theory, because the particle decays that produce neutrinos should also produce gamma rays.

But TXS 0506+056 is a single object, and so far there is little evidence of a broader link between gamma-ray outbursts and neutrino detections. Gamma rays can be blocked by dust and gas near a supermassive black hole, much like the lead apron an X-ray technician wears. Radio waves are not so easily stopped.

That is where the new study, published in October 2026 in The Open Journal of Astrophysics, comes in. In 2017 the Very Large Array in New Mexico began the Very Large Array Sky Survey, or VLASS, tracking how radio emissions from space change in brightness over time. The author's team had already shown that most of the fluctuating radio objects VLASS sees are quasars of the type previously linked to neutrinos. They then compared the times IceCube detected neutrinos with the times VLASS objects flared in radio, and found a correlation: a radio source brightening in the same part of the sky as a neutrino detection, more often than chance would predict.

The limits are plain. The radio flares are associated with only about 13% of IceCube's astrophysical neutrinos, so the origin of the majority remains unexplained. Yet more than 90% of the radio outbursts potentially tied to neutrinos are not seen at all by gamma-ray telescopes. If the sources are hidden in gamma rays but visible in radio, radio telescopes could become an essential tool in neutrino astronomy.

The author calls the signal intriguing, even tantalizing, but not settled. There is about a 1-in-30 chance of seeing these results with no real correlation, roughly the odds of five heads in a row on a coin. Scientists prefer odds nearer one in a million, like twenty heads in a row. Reaching that will take more observations, which the team expects within the next few years.