Scientists have warned that humanity might have missed signals from aliens because they are being disrupted by the conditions of space. Messages from distant planets could be distorted by activity from nearby stars, according to a new study.
Solar weather would broaden an otherwise ultra-narrow signal, spreading it across more frequencies and making it harder to detect. For decades, the Search for Extraterrestrial Intelligence (SETI) has focused on looking for spikes in frequency, as such signals are unlikely to occur naturally and could indicate alien life.
The new research suggests that planets might be sending out very narrow signals that are then smeared by conditions in their own solar system. While astronomers already account for distortions that occur as radio signals travel through interstellar space, the study indicates they may have overlooked distortion happening closer to the source, from the aliens' own suns.
“SETI searches are often optimised 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 Vishal Gajjar, astronomer at the SETI Institute and lead author of the paper.
The researchers measured the possible effect by analysing radio transmissions from spacecraft in our own solar system, allowing them to understand how signals from other planets might be altered as they pass through their star systems. This work enabled them to build a framework for the distortion, which they hope will guide future searches.
“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 research assistant at the SETI Institute. The findings are published in The Astrophysical Journal.
