We might have missed signals from aliens because they are being disrupted by the conditions of space, scientists have warned.
Messages being sent from distant planets could be disrupted by activity from nearby stars, they warn.
That solar weather would broaden an otherwise ultra-narrow signal, which would spread it across more frequencies and make it harder to detect, they say in a new paper.
For the decades that scientists have been looking for alien signals through a work known as SETI, they have tended to look for spikes in frequency. Such signals are thought to be unlikely to be caused by natural processes, so would probably show that they were being sent by alien life.
But the new study suggests that planets might be sending out very narrow signals that are then being spread out or smeared by the conditions in their solar system.
Astronomers already account for the distortions that can happen as radio signals travel through the long journey of interstellar space. But the new study suggests that we might not have accounted for distortion that would happen more near to the source, from their own suns.
“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 Vishal Gajjar, astronomer at the SETI Institute and lead author of the paper.
The researchers measured the possible effect by looking at radio transmissions from spacecraft in our own solar system. That allowed them to understand how such signals would be changed as they were sent from other planets through their own star systems.
The work allowed the researchers to build a framework for how that distortion happens, which they hope to use to help guide the decision on where to look for signals and how to design those 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 work is reported in a new paper, ‘Exo–IPM Scattering as a Hidden Gatekeeper of Narrowband Technosignatures’, published in The Astrophysical Journal.
