Nobody thinks it was a phone call from ET, but radio astronomers admit that they have no explanation yet for a beam of radio waves that appears to have come from the direction of the star Proxima Centauri.

“It’s kind of a technological signal. It’s part of Breakthrough Listen, which is an effort,” said Sophia Sheikh, a graduate student at Pennsylvania State University and trying to decode its source. With a value of $ 100 million funded by Yuri Milner, a Russian billionaire investorTo find strange radio waves. The project has now bogged down in the most interesting dirt yet.

Proxima Centauri is an attractive prospect For “out there over there.”

It is the closest known star to the Sun, just 4.24 light years from Earth, and is part of a three-star system known as Alpha Centauri. Proxima contains at least two planets, one of which is a rocky world slightly larger than Earth, and occupies the so-called habitable zone of the star, where temperatures should be favorable to water, the substance of life, on its surface.

The same radio signal was detected in Spring 2019 and I mentioned earlier in The GuardianIn many ways, alien hunters dream things. It was a 982.02 MHz narrow-band signal recorded by the Parkes Observatory in Australia. Nature, be it an exploding star or a geomagnetic storm, tends to emit over a wide range of frequencies.

“The signal appears to only appear in our data when we look in the direction of Proxima Centauri, which is exciting,” Ms. Sheikh said. “This is a threshold that has never been crossed by whatever signal we saw earlier, but there are a lot of caveats.”

Practitioners of the hopeful field of searching for extraterrestrial intelligence, also known as SETI, say they’ve seen it all before.

“We’ve seen these kinds of signals before, and it always turns out to be radio frequency interference,” writes Dan Wertheimer, the chief technologist at the Berkeley City Research Center, who is not part of the Proxima Centauri study.

This thought was echoed by fellow Berkeley colleague Andrew Simeon, Breakthrough Listen principal investigator. “Our experience is in a sea of ​​interconnected signals,” he said.

“My instinct in the end is that it will be man-made,” he added. “But until now we cannot fully explain this.”

So there’s nothing you guys see here. Until there is. However Claims of bio-signature gases on Venus And the Tales of UFO sightings collected by the PentagonThe discovery of life, not to mention intelligence, would be a psychological thunderstorm of cosmic and historical proportions.

False alarms have been a part of SETI from the start, when Frank Drake, then in Cornell and now retired from the University of California, Santa Cruz, indicated, Radio Telescope in Greenbank, W.1960’s on a pair of stars, hoping to hear the aliens’ radio waves. Find out what appeared to be a signal. Could it be easy to discover that we are not alone?

It turned out to be a secret military experiment.

Sixty years later, we’re officially still alone, and SETI as a project has gone through wars both economically and politically even as technology has enhanced humanity’s ability to comb through an almost endless haystack of planets, stars and the “magic frequencies” they might broadcast on.

It was a breakthrough of listening It was announced with great fanfare by Mr. Milner and Stephen Hawking in 2015, Sparking what Dr. Simeon called a renaissance.

He said, “This is the best time to do SETI.”

The final excitement began on April 29, 2019, when Breakthrough Listen scientists switched the Parks radio telescope on Proxima Centauri, to observe the star for violent glows. It is a small star known as the red dwarf. These stars are susceptible to such explosions, which can strip the atmosphere of a planet and render it uninhabitable.

In total, they recorded 26 hours of data. However, the Parkes Radio Telescope has been equipped with a new receiver capable of resolving narrow-band signals of the kind that the SETI researchers are looking for. So in the fall of 2020, the team decided to dig into data for such signals, a job entrusted to Shane Smith, an undergraduate at Hillsdale College in Michigan and an intern at Breakthrough.

The signal that surprised the team five times appeared on April 29 during a series of 30-minute windows as the telescope was pointed in the direction of Proxima Centauri. He hasn’t appeared since. It was a pure, unmodified tone, which means it does not carry any message other than the fact that it is there.

The signal also showed a tendency to deviate slightly in frequency over 30-minute periods, which is a sign that any signal is coming from that is not on the surface of the Earth, but is often associated with an object that is spinning or rotating.

But the drift does not match the motions of any known planets in Proxima Centauri. And in fact, if the signal was real, it might have come from somewhere outside of Alpha Centauri. Who do you know?

The subsequent failure of the sign led to comparisons to a well-known discovery known as thewow! Signal“Which appeared on a printout of the Big Ear Radio Telescope, operated by Ohio State University in 1977. Jerry Eman, a now retired astronomer, wrote” Wow! “On the side of the printout when he saw it after that fact. The sign did not appear again, it was not satisfactorily explained, and some people still wonder if it was a missed call from Out There.”

Dr. Simeon said of Proxima’s reference, “There were some exclamation points but” Wow “was not one of them.

When asked about them, he laughed.

“At first there were baffled reactions from people, but it settled quickly,” he said.

He said that during a period of 24 to 48 hours at the end of this October, the mood shifted from my curiosity and curiosity to “a very serious scientific investigation work.”

Ms Sheikh, who is expecting to get her PhD next summer, leads the police work. She earned her BA from the University of California, Berkeley, and was intending to enroll in particle physics, but found herself drifting into astronomy instead. I first heard about the Breakthrough Listen and SETI Project on Reddit while she was looking for a new college research project.

Of the supposed signal, she said: “I’d say we were very skeptical at first, and I’m still skeptical.” But, she added, it was the “most interesting signal to come through Breakthrough Listen.”

The team hopes to publish its results in early 2021.

Dr. Wertheimer says the Parkes telescope – which was transmitting communications to the Apollo astronauts – is known for its false alarms. In one recent example, he said, astronomers believed they had discovered a new astrophysical phenomenon.

“It was so exciting that someone noticed that the signals only appeared at lunch hour,” he said. They were coming from a microwave.

Over the years, SETI astronomers have boasted of their ability to track down the source of suspicious signals and eliminate them before words leak to the public.

This time their work was reported by The Guardian. “The audience wants to know, and we understand that,” said Dr. Simeon. However, he and Mrs. Sheikh assert, they are far from over yet.

Mrs. Sheikh said: “Frankly, there is still a lot of analysis that we need to do to be confident that this thing is not an intervention.”

Part of the problem, she explained, was that the original notes were not made according to the standard SETI protocol. Usually, a radio telescope points to a star or other target for five minutes and then “nods” away from it slightly for five minutes to see if the signal continues.

But in Proxima’s observations, the telescope pointed for 30 minutes and then moved away across the sky (30 degrees or so) for five minutes to a quasar that astronomers were using to calibrate the brightness of the star’s glows. Such a large swing might have taken the telescope further from the source of radio interference.

Ms Sheikh said that if all else fails, they will try to reproduce the results by repeating the precise movements of the Parkes telescope again on April 29, 2021.

She said, “Because, if it’s actually coming from Proxima, they’d probably want to send a welcome once a year or something like that.” “But there is likely to be an annual event happening at the visitor center, or something like that, that has an environmental impact that doesn’t happen the rest of the year,” she said.

Proxima’s sign could be destined to pass into a legend like Ohio Wow! Signal, but at SETI there is always another day, another star.

Ms Sheikh said it was fun, even if Proxima ended up indicating an intervention.

“This is very exciting, no matter what comes out of it.”