Neutrinos are funny little particles that weigh almost nothing, making them one of the universe's most elusive building blocks. They can come from objects as mundane as bananas and as exotic as supernovas - the exploding death throes of massive stars. Most neutrinos stream through space and pass through the Earth without interacting with anything.
Author
- Yjan Gordon
Instructor of Physics, University of Wisconsin-Whitewater
An experiment called IceCube, built to detect these "ghost particles" emitted from astrophysical events, just won a Nobel Prize . As a physicist , I'm interested in figuring out where the neutrinos IceCube detects come from. A study that my colleagues and I published in October 2026 suggests that we could potentially use radio telescopes to answer this question.
Even though these telescopes can't see neutrinos, we can use their data to match up IceCube's detections with their potential sources out in space. Knowing which types of objects produce neutrinos can tell astronomers about the physics occurring within those objects.
The shy nature of neutrinos
Most particles interact with the universe through a fundamental force of nature called electromagnetism . It's the force that powers the phone, tablet or computer that you may be reading this article on. It drives all the chemistry responsible for life, and it's responsible for the light your eyes can see.
What makes neutrinos odd is that they don't interact with the universe through electromagnetism. Instead, they interact with the universe via a force that physicists call the weak interaction . This force only acts over distances smaller than the inside of an atomic nucleus ; as such, they must pass very, very close to the centers of atoms in order to interact - otherwise they just fly right through. That makes them very difficult to detect - but not impossible.
Scientists have been able to detect neutrinos from space - called astrophysical neutrinos - since the 1960s. These typically come from our Sun and, in at least one case, from a supernova .
Over the past decade or so, researchers at the appropriately named IceCube Observatory have used the South Pole's Antarctic ice as a neutrino telescope. The densely packed ice gives neutrinos many opportunities to interact with water molecules, and detectors can see radiation from those interactions when they do occur.
Even so, neutrinos really are one of nature's most introverted particles, and it takes time for any of the ice molecules to get lucky and interact with a neutrino. But, with enough time, it eventually happens. And with more time, it happens again. The more time you give it, the more interactions you see, and the more neutrinos you detect.
IceCube has used this approach to detect astrophysical neutrinos that are hundreds of thousands of times more energetic than those previously seen. The discovery of these high-energy astrophysical neutrinos has opened up a new window on our universe.
The same property that makes them difficult to detect - namely their reluctance to interact with their surroundings - also makes them an effective way to see high-energy processes in places that light can't penetrate. The problem is we're not sure where they all come from.
Where could astrophysical neutrinos come from?
Scientists do have some ideas about their origin, of course. Quasars - objects where matter is being ripped apart by black holes millions of times more massive than our Sun - seem to be likely candidates. In 2017, IceCube detected a neutrino that appeared to come from the direction of a quasar , known as TXS 0506+056, at the same time that a telescope detected an outburst of gamma radiation from that same object.
That finding is interesting because the processes that produce neutrinos - namely the decay of subatomic particles - should also produce high-energy electromagnetic radiation - namely gamma rays. So scientists expect neutrino sources to also produce gamma-ray outbursts.
However, TXS 0506+056 is just one object. It may not be representative of where most high-energy neutrinos come from. So far, there's been little evidence of a more general relationship between gamma-ray outbursts and neutrino detections. But gamma rays can be easily obscured.
Much like the lead apron that the technician taking your X-ray at the hospital wears to protect themselves from the radiation, dust and gas that gathers near a supermassive black hole can block gamma rays from ever reaching Earth.
However, another form of electromagnetic radiation that's invisible to gamma-ray telescopes - radio waves - are not so easily shielded. Using telescopes that look at radio waves from space may provide scientists an alternate way to see what's going on.
Using radio telescopes
Beginning in 2017, the Very Large Array in New Mexico began tracking how radio emissions from space change in brightness over time, a project known as the Very Large Array Sky Survey , or VLASS for short. My team and I recently showed that most of the objects seen by VLASS with fluctuating radio emissions are quasars , of the same type that IceCube previously saw producing neutrinos.
Interestingly, when we compared the times that IceCube detected neutrinos with the times when objects spotted by VLASS experienced flares of radio emission, there appeared to be a correlation.
Put another way, when an astrophysical neutrino is detected by IceCube, there is a radio source brightening in the same part of the sky, more often than you'd expect from random chance . These radio flares seem to only be associated with about 13% of the astrophysical neutrinos detected by IceCube, which means we still can't account for the origin of the majority of astrophysical neutrinos. However, more than 90% of the radio outbursts potentially associated with neutrinos aren't seen at all by our gamma-ray telescopes.
If the neutrino's source of origin is hidden at gamma-ray wavelengths, but not at radio wavelengths, then radio telescopes could become an essential tool in neutrino astronomy.
At the moment, the signal we're seeing is intriguing, even tantalizing. But there's about a 1-in-30 chance of getting the results we see even if there's no correlation between neutrinos and radio flares. Those are roughly the same odds as tossing a coin five times and getting heads every time: unlikely, but not impossible.
Scientists are far more comfortable when the odds of a result being due to random chance are closer to one in a million - the same as getting heads 20 times in a row. To confirm if what we're seeing is real or not, we need more observations. We expect to have those in the next few years.
One thing is for sure, though: It's an exciting time to be studying the origins of astrophysical neutrinos, and it looks like radio astronomers may have a big role to play.
Yjan Gordon does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
