For decades we've been watching the skies for signs of extraterrestrial life - but it seems we may have missed their attempts at contact.
A new study casts doubt on our methods of detecting radio signals, arguing that "space weather" can distort incoming transmissions.
While most experiments have focused on identifying sudden increases in radio frequency – signals that are difficult to produce by natural processes in space – experts pointed out an overlooked complication.
Even if an extraterrestrial transmitter produces a very narrow radio signal, it may not remain so when it leaves the atmosphere of its star.
This deformation, which occurs near the point of origin, can "spread out" the signal's frequency, causing it to escape our detectors, which are programmed to look for more concentrated waves.
"Searches are often optimized for extremely narrow signals," said Dr Vishal Gajjar, astronomer at the SETI Institute and lead author of the study.
"If a signal expands from its star's environment, it could slip below our detection thresholds, even if it exists, which could help explain the radio silence we've seen in searches for technosignatures."
For the study, the team analyzed radio transmissions from our probes within the solar system. Using data from the probes, they calculated how turbulent plasma released by stars – like the Sun – affects the radio signals.
This data was used to predict what might happen in a wide range of space environments. They explained that M–dwarf stars, which make up about 75% of the stars in the Milky Way, have the highest probability of distorting the signals.
This discovery could lead to better detection methods that take this into account. This means that even when signals are not “very narrow” when they reach Earth, they could still come from extraterrestrial life.
“By measuring how stellar activity can transform narrowband signals, we can design surveys that are better suited to what actually reaches Earth, not just what can be transmitted,” said Grayce C. Brown, co-author of the study.
In The Astrophysical Journal, the researchers concluded: “The so-called Great Silence, when applied to radio technosignature searches, is not only evidence for the absence of transmitters, but also reflects our detection limitations due to the mismatch between the assumed signal morphology and the extended waveforms. Refitting the non-detections with width-aware methods will clarify how much of the Great Silence reflects the real absence of transmitters versus selection effects.”
The researchers suggest that astronomers keep these findings in mind to ensure that technosignatures “are not systematically missed.”
Scientists believe the best candidates for extraterrestrial life are "Earth-like" planets orbiting distant stars.
One of them is TRAPPIST–1e, an Earth-sized planet just 40 light-years away, located within the habitable zone of its star.
Another promising candidate is K2–18b, which some studies suggest could be teeming with life.
Finally, a NASA veteran declared last week that aliens exist – they just haven't visited Earth yet.
Dr Gentry Lee, who has worked for the US space agency since 1968, said there is no evidence that aliens or their machines have ever visited Earth. “If you believe otherwise, you are being fooled,” he told the AAAS conference in Phoenix.
According to him, in any case of a UFO sighting or alien encounter, there is usually a simpler explanation. But when it comes to distant planets, life "just has to be out there somewhere."
He added: "We will find life in some form somewhere else. The probability is overwhelming."
In 1977, an astronomer in Ohio picked up a radio signal so powerful from Sagittarius that he enthusiastically wrote “Wow!” next to his data.
This 72-second signal, captured by Dr Jerry Ehman, was 30 times stronger than background radiation and has since led to conspiracy theories suggesting it could have been a message from intelligent extraterrestrials. /GazetaExpress/
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