A former analyst with the US Department of Defence is on the trail of an astronomical ‘cold case’ – an unexplained signal that some believe could have come from extraterrestrials

Way back in 1977 something amazing happened (apart from the release of Star Wars obviously). Astronomer Jerry Ehman was using the Ohio State University’s Big Ear radio telescope to sweep the sky for possible signals from extraterrestrial civilisations. He found something.

While pointing towards a grouping of stars called Chi Sagittarii on 15 August, he received a powerful blast of radio waves that lasted for 72 seconds. He circled it on the readout and wrote: “Wow!”

Analysis of the signal showed that it displayed all the hallmarks of coming from interstellar space, and it became something of a cause célèbre for those involved in SETI, the search for extraterrestrial intelligence.

The trouble is that despite numerous attempts, the signal has never been observed again and so remains unexplained. Until now perhaps, thanks to the work of Professor Antonio Paris of St Petersburg College, Florida.

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Before he was an astrophysicist at the St Petersburg College, Paris was an analyst for the US Department of Defence. “I have this investigative background, so I approached the ‘Wow!’ signal as I’m going back to the crime scene,” he told me over Skype. “It’s a cold case, so I went to various [astronomical] databases to find culprits or suspects that were at this crime scene at the time.”

He didn’t find aliens but he did find two suspicious looking comets.

Known as 266P/Christensen and 335P/Gibbs, they have never been investigated before because they were only discovered in 2006 and 2008 respectively. Paris found that they were both in the vicinity of Chi Sagittarii on the day that the ‘Wow!’ signal was detected.

This could be significant because comets are surrounded by clouds of hydrogen gas that are millions of kilometres in diameter. The ‘Wow!’ signal itself was detected by Ehman at 1420MHz, which is a radio frequency that hydrogen naturally emits. He published his idea at the beginning of this year.

But before the case can be closed, Paris must test his hypothesis and for this he needs public support.

Comet 266P/Christensen will pass the Chi Sagittarii star group again on 25 January 2017, while 335P/Gibbs will make its passage on 7 January 2018. Paris plans to observe these events to look for a recurrence of the mystery signal. But time is not on his side for using an existing radio telescope – they are all booked out.

So, he has launched a crowdfunding campaign on gofundme to raise the $13,000 he needs to buy a radio telescope to make the observation. Donations are rolling in and he is already most of the way to his target.

“I would like to [be fully funded] in May, order the stuff so that I can have it by October,” he says. This would give him time to construct the dish, test it and prepare for the January encounter.

Although some other astronomers have voiced scepticism at his hypothesis, Paris points out that even if he turns out to be wrong, it’s still good science because we are learning something about comets, and he and his colleagues have a new radio telescope that they can use for further research.

Also on the plus side; if it isn’t comets, SETI scientists still have their best candidate for an extraterrestrial signal.

Stuart Clark is the author of The Unknown Universe (Head of Zeus), and co-host of the podcast The Stuniverse (Bingo Productions). He is teaching the Guardian Masterclass ‘Understand the Universe in an Evening’ on 23 May.