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Scientists explain intriguing signal picked up while searching for aliens in nearby planetary system

Andrew Griffin
Tuesday 26 October 2021 07:29
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Scientists have finally found an explanation for an intriguing signal seeming to come from our nearest neighbour, found while looking for alien life.

Last year, radio telescopes appeared to be getting data from the Proxima Centauri system that could be indicative of alien technology.

Since then, Breakthrough Listen – a major project to search for life elsewhere in the universe – has been analysing the signal, to find out whether it might really be coming from another civilisation.

They found that the signal in fact appears to be an artifact from human technologies, according to two new papers published in the journal Nature Astronomy.

But Yuri Milner, the Russian billionaire who founded the Breakthrough Listen project, said that the research represented a major step in the search for alien life – despite the fact it had found the opposite in this case.

“The significance of this result is that the search for civilisations beyond our planet is now a mature, rigorous field of experimental science,” he said.

Those astronomers who look for signs of alien civilisations, or technosignatures, have to pick through the variety of similar signals that are coming to us from Earth. Radio telescopes must try and pick through all of the radio signals created by humanity – from our phones, television transmitters, radar systems and more – and filter them out from any possible signals coming from Earth.

The latest papers concentrate on the effort to do that at the CSIRO Parkes Telescope in New South Wales, Australia, which is one of the pieces of equipment involved in the Breakthrough Listen search. That telescope was used to scan Proxima Centauri, our nearest star after the Sun, which is only 4 light years away and has at least two planets orbiting it.

To better examine it, astronomers looked at it through a variety of radio frequencies. The research was the equivalent of tuning into more than 800 million radio channels at one time, Breakthrough Listen.

When planets are examined in this detail, a whole host of signals are likely to be picked up. As such, Breakthrough Listen runs any observations through a filter that sorts out signals that are not likely to come from a transmitter away from Earth: whether the signal changes in frequency over time, and whether they are coming from the direction of the target, which can be established by looking whether they switch off when the telescope points away.

That filters out the vast majority of signals received by Breakthrough Listen. But even after that, last year’s intriguing signal remained.

What’s more, it had some of the characteristics that might suggest it really was coming from an alien civilisation. That led to the possibility that the Breakthrough Listen team really had found a signal coming from aliens.

But further examination found that the signal does not in fact appear to be alien – but altogether more human. While they were not able to find exactly what had caused the detection, it appears it was just specifically calculated to slip through the filters.

It does however give scientists confidence that they would be able to identify real signals from alien civilisations.

“While we were unable to conclude a genuine technosignature, we are increasingly confident that we have the necessary tools to detect and validate such signatures if they exist,” said S Pete Worden, executive director of the Breakthrough Initiatives.

They also believe that Proxima Centauri is still an exciting prospect for finding technosignatures.

“In the case of this particular candidate, our analysis suggests that it’s highly unlikely that it is really from a transmitter out at Proxima Centauri. However, this is undoubtedly one of the most intriguing signals we’ve seen to date,” said Andrew Siemion at the University of California, Berkeley, who leads the Breakthrough Listen science team.

The two papers – ‘A radio technosignature search towards Proxima Centauri resulting in a signal of interest’, which details the discovery of the signal, and ‘Analysis of the Breakthrough Listen signal of interest blc1 with a technosignature verification framework’, which explains the analysis of it – are both published in Nature Astronomy today.

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