Researchers at the SETI Institute suggest that solar wind and plasma from stars could distort radio signals from distant intelligent life, making them harder to detect. This means past searches may have overlooked potential evidence by focusing on narrowband signals. Adjusting detection methods could improve future chances of discovery.
The Search for Extraterrestrial Intelligence (SETI) Institute has long scanned the skies for sharp, narrowband radio signals that might indicate intelligent alien life. However, a new study indicates that space weather, including solar wind and stellar plasma, can broaden and weaken these signals as they travel through space.
Vishal Gajjar and Grayce Brown, researchers at the SETI Institute, modeled the effects based on radio transmissions from spacecraft in our solar system and extended the findings to other stars. Their calculations show that a 100 megahertz signal could widen by up to 100 hertz, potentially falling below standard detection limits. During intense space weather events, this broadening can increase by several orders of magnitude.
Simon George, also at the SETI Institute, notes a shift in thinking: "The idea that an intelligent civilisation would send out such signals is becoming dated, especially when you look at how communications and so forth have evolved since the 1960s." He points out that modern Earth communications favor broadband and spread-spectrum techniques, which carry more data but produce wider signals. In the 1960s, Earth emitted stronger narrowband signals, a trend that has declined over time.
John Elliott from the University of St Andrews views the research positively. "It’s over 50 years that we’ve been actively researching and that’s a blink of the eye," he says, highlighting how improving computing power and AI could help extract signals from noise in the future.
Eric Atwell from the University of Leeds estimates this insight might double the slim odds of detection, from 0.0001 percent to 0.0002 percent. He questions passive listening, suggesting that if aliens wish contact, they might send clearer signals. Meanwhile, groups like Messaging Extraterrestrial Intelligence (METI) advocate active broadcasting to nearby stars.
The findings appear in The Astrophysical Journal (DOI: 10.3847/1538-4357/ae3d33).