by Aliens may be waiting until a cosmic version of ‘high noon’ to send out their signals to us, scientists have suggested.
In a new study, scientists hunted for technological signs of ET at the moments when exoplanets pass directly in front of their suns, from Earth’s point of view. These exact moments could be the perfect chance for an alien world to send out a signal to Earthlings in an attempt to make contact.
“Exoplanetary transits are special because they can be calculated by both us on Earth, as observers, and also all potential technological species in the exoplanetary system itself, as the transmitters,” said study leader Sofia Sheikh (opens in a new tab), a postdoctoral fellow in radio astronomy at the Search for Extraterrestrial Intelligence (SETI) Institute. These transits are therefore a predictable and repetitive time when aliens can think of sending messages and earthlings can look to receive them.
“This strategy helps us narrow down the big question of where and when to look for a message in space,” Sheikh told LiveScience in an email.
The new study, published Dec. 9 on the preprint page arXiv (opens in a new tab) and scheduled for peer-reviewed publication in The Astronomical Journal, found no evidence of chatty aliens. But the study only sought a dozen distant planets. In the future, they plan to look further with a variety of telescopes.
Related: Is it time to send another message to intelligent aliens? Some researchers think so.
Since radio technology was invented in the late 19th century, Earth have leaked transmissions into space – and sometimes, as with the famous one Arecibo message from 1974, have been sending them out deliberately in hopes of contacting any intelligent extraterrestrial human who is listening. In the hope that intelligent alien civilizations may also be leaking technological signals, or technosignals, scientists are also scanning the galaxy for radio waves which may originate from alien technology.
But galaxy is a big place, so a key question is where to look. Sheikh and her team decided to eavesdrop on distant exoplanets as they pass in front of their sun, in what is known as a “Schelling point” – a solution to a problem that two individuals tend to default if they don’t communicate with another. In other words, the moment of planetary transit just seems like the logical moment to connect from both the sender’s and the receiver’s point of view.
Sheikh and her colleagues used West Virginia’s Robert C. Byrd Green Bank Telescope to search for radio signals from 12 exoplanets whose transits could be observed during a short window in March 2018. They detected many radio signals — nearly 34,000, in fact — but 99, 6% of these can be rejected as interference from earth-bound communication. A group of trained citizen scientists did the work of investigating the signals.
In the end, all but two of the signals were determined to be due to interference. The remaining two, a pair of short bursts from Kepler-1332b and Kepler-842b – both potentially rocky planets larger than Earth – were deemed worthy of further follow-up. However, Sheikh said, these two are also almost certainly due to interference and are not genuine messages.
Still, she said, the study was proof that the search method can work. The researchers plan to tackle more observations in the future at the SETI Institute’s Allen Telescope Array in California.
