What’s causing the Wow! signal?
Astronomers have sought to explain a mysterious one-off ‘alien’ signal – could we be any closer to an answer?
On 15 August 1977 the Big Ear radio telescope belonging to Ohio State University scanned the night sky. There was nothing unusual about this. Turned on for the first time in 1963, the telescope had long been used to search for extraterrestrial radio signals, churning out reams of computer printouts via an IBM 1130 mainframe computer that would then be looked at in fine detail by the observatory’s astronomers.
Each time someone so much as glanced at one of the jam-packed pieces of paper, they hoped to see something significant: evidence, no matter how small, that life may be out there. So when astronomer Jerry Ehman studied the data taken from that warm summer’s night a few days later, he was startled. Staring at him in a vertical line was the baffling sequence of numbers and letters ‘6EQUJ5’. ‘Wow!’ he wrote, highlighting the sequence with a circle of red ink.
Since the discovery was made, there has been much debate over the source of the signal. We know for certain that it was detected as it passed across the telescope’s field of view at 22:16 EST that night, and we know it was coming from a grouping of stars called Chi Sagittarii. We understand that it lasted for 72 seconds – and that it has never been detected since, not even in the weeks following the original discovery.
Perhaps most crucially, the frequency of this one-off signal was also very close to what is known as the 21-centimetre line, or hydrogen line. This is important because back in the 1960s and 1970s, it had been hypothesised that extraterrestrials looking to communicate would most likely use the most abundant element in the universe: hydrogen. This emits a radio frequency of 1,420MHz, which is exactly what was picked up by Big Ear.
“When this signal was detected at 1,420MHz, which indicated hydrogen being present in a part of the sky that had always been known to be quiet, it was like, ‘oh my god! It must be aliens’,” says Antonio Paris, a professor at St Petersburg College in Florida. It explains why the ‘Wow! signal’, as it quickly became known, has long been associated with the possibility that it was sent by extraterrestrial life. That it was discovered in the same year as the Hollywood releases of Close Encounters of the Third Kind and Star Wars was simply a delicious coincidence.
By the mid-1980s astronomers were coming to the conclusion that it was most likely caused by a natural phenomena that had simply been undetectable. “But by then it had already become part of folklore and legend, and it had become hijacked by the science-fiction community, which has shaped it as evidence of life,” Paris tells us. This, he says, had made life a little more difficult for astronomers looking to get to the bottom of what may have happened. “I started to explore the Wow! signal myself 11 years ago, and my findings are hurting the feelings of a lot of people,” he says.
And indeed they are. In January 2016 Paris hit the headlines when he claimed the signal may have been caused by a passing comet that astronomers had yet to spot and catalogue. He pinpointed two potentials: 266P/Christensen, which was discovered in 2006, and 335P/Gibbs, which was spotted a couple of years later. These, he said, were moving through Chi Sagittarii on that memorable day in August 43 years ago. To test whether they were giving off signals that could match Wow!, Paris vowed to point a telescope at them when they passed Earth in January 2017.
Since his theory relies on comets releasing a lot of hydrogen when they orbit around the Sun – a cloud of gas being emitted when the frozen water is broken up by ultraviolet light – he hoped to be able to pick up a 1,420MHz signal in the spot where the Wow! signal was detected by Big Ear. Like the original telescope, he focused on a certain spot in the night sky. “We pointed a ten-metre telescope at 266P/Christensen on various occasions and the response was 1,420MHz, which is what we have reported,” says Paris, who published a paper in the Journal of the Washington Academy of Sciences detailing just that in June 2017.
Almost immediately, other astronomers sought to dismiss the findings. Dr Seth Shostak, a senior astronomer at the SETI Institute, which leads the way in the search for extraterrestrial life, claimed the comet hypothesis does not work. Much rests on the fact that a single 72-second signal is all that was ever detected in 1977.
“There are many reasons, but one that I personally think is strong is to consider that the
“I STARTED TO EXPLORE THE WOW! SIGNAL SEVEN YEARS AGO, AND MY FINDINGS ARE HURTING THE FEELINGS OF A LOT OF PEOPLE”
ANTONIO PARIS
Ohio State University Radio Observatory had two feed horns – essentially two receivers,” Shostak tells
All About Space. “It would observe whatever it was pointed at twice, separated by 70 seconds. The Wow! signal was found the first time, but it was not seen the second time. I worked the numbers, and unsurprisingly there was no way that the comet could have moved across the sky far enough to be out of the field of view of the second feed in just over a minute.”
Paris sticks by his findings, claiming he always knew they would be attacked. “Before we hit that send button on our paper, I told my staff to be ready for lots of criticism,” he says. He vows to repeat the experiment, but do it slightly differently next time. Rather than employing drift scanning, which meant their ten-metre telescope in Florida remained fixed while the object moved, “our next experiment will have the telescope move at the same speed as the comet so we will get a continuous signal, and that will answer a lot of questions”.
Someone who is sure to be interested in the answers is Chris Lintott, professor of astrophysics at Oxford University. Like all astronomers, he is aware that there have been numerous failed attempts to redetect the Wow! signal, and that any claim to suddenly find an answer will always be greeted with scepticism. So far devices much more sensitive than Big Ear have only ever picked up faint sources of radio emissions that are certainly nothing of the intensity of Wow!. What, then, does Lintott make of the claim that comets are potentially to blame?
“Using drift scanning, the object should have traversed the field of view in about five minutes, but the signals he sees last for about 45 seconds so they’re not coming from an object traversing the main beam,” he tells us. “There is also a claim of neutral hydrogen around the comet at the 21-centimetre line, and I don’t believe that detection is really of the comet he is pointing the telescope at. If comets were as bright as he claims in the 21-centimetre line, they’d be picked up by large surveys of the sky that have been done for many decades. But we just don’t see them.”
Still, Paris, a former analyst of the US Department of Defense, insists he has covered as many bases as possible. He initially approached the Wow! signal as if he was revisiting a crime scene, looking closely at astronomical databases for clues as to what could have caused the signal. “We have tried to debunk the theory as much as possible,” he tells us, having attempted to eliminate lines of enquiry.
He has also split his investigations into three parts. “The first was the hypothesis, the second was finding the culprit, which we think is comets now, and the third is to look at how it is possible that these comets are not doing what they are supposed to be doing.” In other words he will seek to discover why astronomers have never detected hydrogen emission from comets before. His research since has been focused on how is it possible that 1,420MHz can be detected from a comet – if this is common, it could help his comet theory.
It’s something Alan Fitzsimmons, an astronomer at Queen’s University Belfast, would no doubt like to
“Before we hit that send button on our paper, I told my staff to be ready for lots of criticism”
Antonio Paris
see too. He has said that 266P/Christensen displays little activity when it is at its closest point to the
Sun – its perihelion. “There would have been no hydrogen coma to detect,” he is quoted as saying. So what did Paris see?
“This is not about what Paris saw or what Paris believes – it is what the telescope was telling us,” he says. “[We used] an old NASA telescope that was refurbished with thousands of dollars. The engineers who built it for us are professionals, and they are standing by those results too. It’s not like something we pulled out of our butts and wrote a paper [about].”
Even so, many astronomers remain to be convinced, and there are also questions being asked of the journal in which the findings appeared. “I’d say there are journals, and there are journals, and what I know about this journal is that it doesn’t publish much astronomy,” says Lintott. “My guess is that this wasn’t reviewed by an expert in radio astronomy or comets, and the reaction of astronomers when they have seen it online has been pretty negative. If Paris submitted this work to one of the mainstream journals, then the community would have given good feedback and we’d have helped him develop a better experiment.”
Again Paris is able to explain and defend. “It was peer-reviewed,” he insists. “The journal is wellrespected with Nobel Prize winners. The objection is that an astronomy paper did not go through the usual channels, but I did that for a reason. The American Astronomical Society, of which I’m a member, is limited in scope: there are fewer than 8,000 members. If I put a paper in the normal channels, I would expect 2,000 people would read it, and it would be barely noticed in the media.
But with the power of the internet and social media I can circumvent that. I have thousands of followers on Twitter that I can reach out to and get an unbelievable response. It worked because I had
30,000 downloads of this paper, which would never have happened if it was buried among others.”
With that in mind, it is likely the final paper will also end up outside of the mainstream astronomical journals as Paris prepares to push ahead with his third stage of investigation. “What is important right now is how many comets can emit a 1,420MHz source: is it a handful of comets or all of them?” he asks. “And that is a new subject, looking at how these comets differ from each other. We’ll have the final paper published in a few years, and it will answer some of the critics’ questions.”
In the meantime, explanations remain up in the air, just as they have for four decades, which means other possibilities for the signal such as gamma-ray bursts or potential radio interference remain on the table. “The Ohio State folks I talked to about this long ago figured it was just terrestrial interference,” says Shostak. “The basic problem in science is that if you see a strange phenomenon only once, it’s hard to say much about it. It could be many things, but it’s not legitimate to call it an alien signal.”
Although that would disappoint some –
“everyone wants it to be an alien. Of course you want it to be an alien,” laughs Lintott – Paris’ experiments may at the very least eliminate one theory. “In some sense he has carried out a good experiment,” Lintott tells us. “You could think of every other possible explanation for the signal and test them too.”
What, though, if Paris is right? “It would change our understanding of comets,” says Lintott. And if he is wrong? He is already receiving hate mail about his paper. “They are from the UFO community, and I can’t respond to those,” says Paris. Will he regret even exploring this phenomena? “No,” he counters, promising that he would be more than happy to throw up his arms and admit to being wrong if that was indeed the case. “There’s nothing wrong about being wrong. I’m not getting emotional about it,” he says. Instead he’d be more than pleased that his investigations have made an impact.
“The theory has been getting criticism, but I think that is the whole purpose of any science,” he explains. “To spark questions that eventually lead to more science. But I think we are at the point where there has been a lot of discussion about whether the comet could be the culprit or not, so the intention of the paper has been a success. It has opened the door to a mystery that has been dormant for a long time.” Whether it stays that way remains to be seen.