No one believes it was ET telephony, but radio astronomers admit they have no explanation for a beam of radio waves apparently coming from the direction of the star Proxima Centauri.
‘It’s a kind of technological signal. The question is whether it’s Earth technology or technology from somewhere out there, ”said Sofia Sheikh, a graduate student at Pennsylvania State University who leads a team studying the signal and trying to decipher its origins. She’s part of Breakthrough Listen, a $ 100 million effort funded by Yuri Milner, a Russian billionaire investor, to find alien radio waves. The project has now stumbled upon its most intriguing wage garbage to date.
Proxima Centauri is an inviting prospect “over there”.
It is the closest star to the sun, just 4.24 light years from Earth, and is part of a triple star system known as Alpha Centauri. Proxima has at least two planets, one of which is a rocky world only slightly heavier than Earth, which occupies the star’s so-called habitable zone, where the temperature should be conducive to water, the stuff of life, on it surface.
The radio signal itself, detected in the spring of 2019 and previously reported in The Guardian, is in many ways the stuff of alien hunters’ dreams. It was a narrowband signal with a frequency of 982.02 MHz, as recorded at the Parkes Observatory in Australia. Nature, be it an exploding star or a geomagnetic storm, tends to emit on a wide variety of frequencies.
“The signal only seems to appear in our data when we look towards Proxima Centauri, which is exciting,” said Ms Sheikh. “That’s a threshold that has never been crossed by a signal we’ve seen before, but there are many caveats.”
Practitioners of the hopeful field of the quest for alien intelligence, also known as SETI, say they’ve seen it all before.
“We’ve seen these kinds of signals before, and it always turned out to be RFI, radio frequency interference,” Dan Werthimer, chief technologist at the Berkeley SETI Research Center, who is not part of the Proxima Centauri study, wrote in an email. .
That thought was echoed by his Berkeley colleague Andrew Siemion, who is Breakthrough Listen’s lead investigator. “Our experiment takes place in a sea of disturbing signals,” he said.
“My instinct is ultimately that it will be anthropogenic in origin,” he added. “But we can’t fully explain it so far.”
So there’s nothing to see here, folks. Until there is. Despite claims of biosignature gases on Venus and stories of UFO sightings collected by the Pentagon, the discovery of life, let alone intelligence, there would be a psychological thunderbolt of cosmic and historical proportions.
False alarms have been part of SETI since the very beginning, when Frank Drake, then at Cornell and now retired from the University of California, Santa Cruz, pointed a radio telescope in Green Bank, W.Va. in 1960 at a few stars , hoping to hear the radio waves from aliens. He discovered what appeared to be a signal. Could it be that easy to discover that we are not alone?
It turned out to be a secret military experiment.
Sixty years later, we are still officially alone and SETI as a company has lived through the wars economically and politically, even as technology has increased humanity’s ability to search the nearly infinite haystack of planets, stars and ‘magical frequencies’ on which they maybe broadcast.
Breakthrough Listen was announced with much fanfare in 2015 by Mr. Milner and Stephen Hawking, which led to what Dr. Siemion called a renaissance.
“This is the best time to do SETI,” he said.
The recent excitement began on April 29, 2019, when Breakthrough Listen scientists pointed the Parkes radio telescope at Proxima Centauri to monitor the star for violent flares. It is a small star known as a red dwarf. These stars are prone to such outbursts, which can remove a planet’s atmosphere and render it unlivable.
In total, they recorded 26 hours of data. However, the Parkes radio telescope was equipped with a new receiver capable of resolving narrow-band signals of the type SETI researchers are looking for. So in the fall of 2020, the team decided to search the data for such signals, a job that fell to Shane Smith, a student at Hillsdale College in Michigan and an intern at Breakthrough.
The signal that surprised the team appeared five times on April 29 during a series of 30-minute windows that pointed the telescope in the direction of Proxima Centauri. It has not been released since. It was a pure unmodulated tone, meaning that it seemed to carry no message other than the fact of its own existence.
The signal also showed a tendency to drift slightly in frequency during the 30 minute intervals, a sign that the signal from wherever it is coming is not on the Earth’s surface, but often correlates with a rotating or orbiting object.
But the drift does not match the movements of known planets in Proxima Centauri. And in fact, if it is real, the signal could come from somewhere other than the Alpha Centauri system. Who knows?
The subsequent failure of the signal has led to comparisons to a famous detection known as the “Wow! Signal” that appeared on a printout from the Big Ear radio telescope operated by The Ohio State University in 1977. Jerry Ehman, a now retired astronomer, wrote ‘Wow!’ on the side of the print when he saw it afterwards The signal never appeared again, nor was it satisfactorily explained, and some people still wonder if it was a missed call from Out There.
About the Proxima signal, Dr. Siemion said: “There have been some exclamations, but ‘wow’ has not been one of them.”
Asked what they were, he laughed.
“Initially there were perplexed reactions from people, but it quickly settled down,” he said.
Over a 24- to 48-hour period in late October, he said, the mood shifted from curious and curious to “very serious scientific research.”
Ms. Sheikh, who expects to graduate this summer, is leading the detective work. She received her undergraduate degree from the University of California, Berkeley, with the intention of studying particle physics, but found herself going into astronomy instead. She first heard about the Breakthrough Listen project and SETI on Reddit while looking for a new undergraduate research project.
“I would say we were extremely skeptical at first, and I remain skeptical,” she said of the alleged signal. But she added that this was “the most interesting signal for getting through the Breakthrough Listen program.”
The team hopes to publish the results in early 2021.
The Parkes telescope – which once relayed communications to the Apollo astronauts – is notorious for false alarms, says Dr. Werthimer. In a recent example, he said, astronomers thought they had discovered a new astrophysical phenomenon.
“It was very exciting until someone noticed that the signals only appeared during the lunch hour,” he said. They came from a microwave.
Over the years, SETI astronomers have taken pride in their ability to track down and eliminate the source of suspicious signals before the news leaked to the public.
This time their work was reported by The Guardian. “The public wants to know, we get that,” said Dr. Siemion. But, as he and Ms. Sheikh emphasize, they are far from finished.
“To be honest, there is still a lot of analysis we need to do to make sure this is not interference,” said Ms Sheikh.
Part of the problem, she explained, is that the original observations were not made according to the standard SETI protocol. Normally, a radio telescope would point at a star or other target for five minutes and then nod away from it for five minutes to see if the signal continued.
However, in the Proxima observations, the telescope pointed for 30 minutes and then moved far across the sky (about 30 degrees) for five minutes to a quasar that the astronomers used to calibrate the brightness of the star’s flares. Such a big swing could have taken the telescope away from the source of the radio interference.
If all else fails, Ms Sheikh said, they will try to reproduce the results by re-replicating the exact movements of the Parkes telescope on April 29, 2021.
“Because,” she said, “if it’s really from Proxima, maybe they want to send a hello once a year or something.” She continued, “But it’s more likely there is some sort of annual event happening at the visitor center, or something like that, that will cause an environmental impact that doesn’t happen the rest of the year.”
The Proxima signal could be destined to turn into a legend, like the Ohio State Wow! Signal, but in SETI there is always another day, another star.
It was nice, Ms Sheikh said, even when the Proxima signal turns out to be interference.
“This is extremely exciting no matter what comes out.”