- Astronomers have searched for alien radio signals for decades. But there are still no confirmed detections. Is space weather to blame?
- Space weather is the flow of energy and particles from the sun and other stars through space. Its presence in space could disrupt some types of artificial radio signals, says a new study from the SETI Institute.
- The researchers found similar effects on human-made radio signals from spacecraft in our own solar system, as the craft encounter our sun’s space weather.
Why no radio signals from aliens?
For decades, astronomers have looked for radio signals from alien civilizations. They call this endeavor SETI, the Search for Extraterrestrial Intelligence. But so far, they haven’t found any confirmed signals from aliens. Why not? On March 5, 2026, two researchers at the SETI Institute in Mountainview, California, offered an explanation.
They said the answer might be space weather from our sun and other stars. That is, the restless activity of our sun and other stars in our Milky Way galaxy – as they send energy and particles sweeping across space – might be making signals from aliens harder to detect. So things like our sun’s solar wind (or the stellar winds from other stars) and coronal mass ejections (great burps of material from our sun and other stars) might cause artificial signals to broaden and weaken so that they become unrecognizable. They said a signal might be “blurred” before it ever leaves its home star system.
In fact, the researchers say that our sun’s space weather affects radio signals close to home, including signals from spacecraft in our own solar system.
The researchers published their peer-reviewed findings in The Astrophysical Journal on March 5, 2026.
What is space weather?
Overall, space weather includes a constant stream of turbulent charged particles (mostly electrons and protons) flowing outward from our sun’s outer atmosphere. We call this stream of particles the solar wind when speaking of our sun and solar system. We call it stellar wind when speaking of other stars.
Space weather also includes coronal mass ejections (CMEs), or great burps of solar materials and magnetic fields that leave the sun’s surface and travel across space.
When strong streams of solar wind or strong CMEs reach Earth, they can create displays of beautiful auroras. But they can also affect earthly technologies such as power grids on Earth’s surface and satellites in space.
Search for narrowband radio signals
Meanwhile, for the most part, SETI astronomers have focused most of their efforts on the search for intelligent radio signals. They typically search for narrowband radio signals, which occupy a narrow range of frequencies or have a small fractional bandwidth. On Earth, these sorts of signals are typically artificial, not natural. That’s why astronomers look for them in space as possible evidence of extraterrestrial civilizations. They are unlikely to be produced by natural earthly or astrophysical phenomena.
In fact, astronomers have made some detections of such narrowband signals. But they haven’t been able to verify any of them as artificial. Usually the signals have turned out to be earthly interference. Or the signals didn’t repeat, so that astronomers could re-observe them. In that case, we don’t know what they are.
PRESS RELEASEA new study by researchers at the SETI Institute suggests stellar “space weather” could make radio signals from extraterrestrial intelligence harder to detect. Stellar activity and plasma turbulence near a transmitting planet can broaden… ?
— SETI Institute (@setiinstitute.bsky.social) 2026-03-05T18:04:09.569Z
Does space weather affect alien radio signals?
But now, two researchers at the SETI Institute, Vishal Gajjar and Grayce C. Brown, have proposed a possible explanation for the dearth of signals. Intriguingly, they suggest that space weather might be to blame. Space weather is the environment around a star – including our own sun – where stellar winds of charged particles (plasma) stream out from the star. There can be turbulence in those winds, just like turbulence in our atmosphere. Coronal mass ejections are also part of space weather. These are huge eruptions of plasma from the surface of a star.
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Space weather could distort narrowband alien radio signals
The new study found that space weather can “smear” a narrowband signal, making it more diffuse and weaker. This happens before the signal has even left the star system it originated from. So, by the time astronomers here on Earth detect it, it is already blurred so much as to be almost indistinguishable from natural broadband signals. Lead author Gajjar said:
SETI searches are often optimized for extremely narrow signals. If a signal gets broadened by its own star’s environment, it can slip below our detection thresholds, even if it’s there, potentially helping explain some of the radio silence we’ve seen in technosignature searches.
Spacecraft in our solar system
The researchers tested the hypothesis further by using radio signals from active spacecraft in our own solar system. Our sun emits plasma in the solar wind. With this in mind, the researchers calibrated how the plasma broadens the narrowband radio signals from the spacecraft. Then, they extrapolated those results to a wide range of different stellar environments around various stars.
The results show how space weather can affect narrowband radio signals around different types of stars. This is true for red dwarf stars in particular, which are very active and emit more radiation and plasma than our sun. Plus, they are the most numerous type of star in our galaxy. Astronomers could now adapt future searches with the new findings in mind. As co-author Brown noted:
By quantifying how stellar activity can reshape narrowband signals, we can design searches that are better matched to what actually arrives at Earth, not just what might be transmitted.
Bottom line: Astronomers have looked for radio signals from aliens for decades. But none have been confirmed. A new study says space weather could make their detection difficult.
Source: Exo–IPM Scattering as a Hidden Gatekeeper of Narrowband Technosignatures
Via Space Institute
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