The signal was detected by the Parkes telescope in Australia in April and May 2019, with scientists unable to find a source of the waves that could come from Earth.
The frequency is around 980MHz and is particularly narrow, with the changes in frequency consistent with the movement of the planet, The Guardian reports.
Scientists are preparing a paper on the signal, which has been named BLC1 (Breakthrough Listen), but have stressed that it is unlikely to be caused by aliens.
“The Breakthrough Listen Team has detected several unusual signals and is carefully investigating. These signals are likely interference that we cannot fully explain. Further analysis is currently being undertaken,” tweeted Pete Worden, chairman of the Breakthrough Prize Foundation, following The Guardian’s report.
“No one is claiming it’s a technosignature. We are in the process of following the agreed protocols. At this point we have some interesting signals we believe are interference but as of yet have not been able to track down the source.”
The radio waves have not been spotted since their initial observation, an individual from the astronomy community told the newspaper, requesting anonymity because the work is still continuing.
“It is the first serious candidate since the ‘Wow! signal’,” they said, referring to an exceptionally powerful blast of radio waves which appeared to have come from an area near the M55 star cluster in 1997.
Drawing attention to the mysterious transmission on a printout, astronomer Jerry R. Ehman circled the signal and jotted down 'Wow!' next to it.
“It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before,” Sofia Sheikh, from Penn State University, told Scientific American.
Sheikh is a lead author on a paper that will reveal analysis of the signal for Breakthrough Listen, expected to be published in early 2021.
Scientists will have to run additional checks on the signal that the Breakthrough Listen team have never conducted before, according to Jason Wright at Pennsylvania State University, speaking to New Scientist.
Proxima Centauri is a focus of investigation because scientists know there are at least two planets around it.
One planet, the size of Earth, is called ‘Proxima b’. It has a mass of 1.17 Earths and is located in the habitable zone of the star. It is believed this planet could be “likely” to be able to support alien life forms.
“Proxima is also neat because some people have speculated that if there is a lot of technology in the galaxy and if you wanted to communicate over long distances, sending the signal directly is a pretty inefficient way to do it,” says Wright.
“It’s like how if I call you on the phone, my mobile phone is not directly sending your phone a radio signal”, he added. Wright believes the chance of the signal being caused by humans is “99.9 per cent".
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