Since the early 1960s, the search for extraterrestrial intelligence (SETI) has sought evidence of advanced civilizations elsewhere in the cosmos. However, astronomers may have missed any signs of their attempts at communication by relying only on a specific type of radio signal: extremely narrowband transmissions.
Now, a new study released on March 5 by researchers at the SETI Institute suggests that this strategy might unintentionally cause scientists to overlook potential alien communications.
The new findings suggest that “space weather” surrounding distant stars could change or distort radio signals before they ever leave their home star systems. SETI researchers suggest that even if an advanced civilization were to send a perfectly narrow radio signal, turbulent conditions related to emissions from nearby stars could distort it in ways that make it difficult for Earth-based telescopes to detect.
The key factor is plasma, as stellar winds constantly carry plasma outward, and powerful stellar eruptions can inject more turbulence into the environment. When radio waves pass through these fluctuating plasma regions, their frequencies can spread slightly. Instead of being concentrated at a single narrow frequency, the signal becomes broadened, distributing its energy across a wider range of frequencies. As a result, the signal’s peak strength becomes weaker.
Traditional search algorithms used in many SETI experiments are designed to detect very sharp signals. If a signal is broadened even slightly, it may fall below the detection thresholds of these systems. Another way of looking at it is that a genuine ET transmission could still be detected, although it may appear too faint or too dispersed to be recognized by astronomers as an artificial signal.
“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,” said Dr. Vishal Gajjar, an astronomer at the SETI Institute and lead author of the recent paper.
To estimate the degree of signal distortion, the researchers analyzed radio transmissions from spacecraft within our solar system. Because these signals travel through the stormy plasma around our Sun, scientists can measure how the plasma affects radio waves. The team does this by calibrating their models using these measurements.
“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,” said Grayce C. Brown, co-author of the study and a research assistant at the SETI Institute.
Overall, the findings suggest that this effect is strongest around active stars, especially M dwarfs, which make up about 75% of the Milky Way and are common targets for searches for habitable planets. This type of stellar activity can distort signals before they leave the system.
The study also provides a framework for estimating signal broadening across star types and frequencies, helping refine target selection and detection methods. Overall, the so-called “radio silence” may not mean no one is transmitting; it just means our human instruments may simply have been listening for the wrong type of signal.
Chrissy Newton is a PR professional and the founder of VOCAB Communications. She currently appears on The Discovery Channel and Max and hosts the Rebelliously Curious podcast, which can be found on YouTube and on all audio podcast streaming platforms. Follow her on X: @ChrissyNewton, Instagram: @BeingChrissyNewton, and chrissynewton.com. To contact Chrissy with a story, please email chrissy @ thedebrief.org.