In December 2020, what appeared to be a remarkable discovery was made by the Breakthrough Listen project, an ambitious, privately funded group doing its own research into the search for extraterrestrial intelligence (SETI). As The Debriefreported, the team had detected a signal apparently coming from the vicinity of Proxima Centauri that seemed different from the random noise made by all of the other objects in the universe. Their system includes many layers of filters designed to weed out the interesting–but likely non-alien signatures–produced by noisy phenomena such as stars or black holes, and this new signal passed all of the initial tests.
This generated a great deal of interest and excitement in the scientific community. Dr. Andrew Siemion from the University of California, Berkeley, the project’s principal investigator, admitted why this was such an enticing investigation. “The reason we’re so excited about SETI and why we dedicate our careers to it, is the same reason why the public gets so excited about it. It’s aliens! It’s awesome!”
Nearly a year later, however, the general sense of excitement may need to be dialed back a bit. After pouring over all of the data and applying multiple filters, the team recently determined that BLC1 (the name given to the signal, Breakthrough Listen Candidate 1) was unlikely to be an example of ET phoning home. In fact, in a new paper published by Sofia Sheikh (a graduate student at Penn State University and leader of the team that performed the follow-up analysis of the signal) et al, it is revealed that BLC1 most likely originated from a source much closer to home than Proxima Centauri. In fact, it probably came from our own planet.
SO IF IT WASN’T A Signal From Proxima Centauri, WHAT WAS IT?
While disappointing to those hoping for some solid evidence pointing to a potential non-terrestrial intelligent civilization, the team concluded that the original source was most likely something here on our own planet. “It is human-made radio interference from some technology, probably on the surface of the Earth,” Dr. Sheikh told the journal Nature.
But when the original announcement was made in December of 2020, Breakthrough Listen seemed to indicate that the original source was most likely in the Alpha Centauri triple star system, roughly four light years from our sun. Precisely how difficult is it to pin down the source of an energetic transmission of that type? The Debrief reached out to Dr. Jason T. Wright, a professor of astronomy and astrophysics at Penn State University and the director of the university’s Extraterrestrial Intelligence Center for some clarity.
“An astronomical radio telescope is exquisitely sensitive,” Dr. Wright said, “and in addition to greatly amplifying signals from things it is pointed at, it can also weakly detect signals coming from all around it. Telling the difference requires some sort of discriminant. In this case, they occasionally ‘nodded’ the telescope to another point in the sky. Then, any signals from Proxima would have gone away, but all of the signals coming from human sources should keep going on. Except in this case, the mystery signal went away whenever they pointed away, and came back most of the times they pointed at Proxima. It was literally a one-in-a-million sort of thing.”
SO WHERE DO WE STAND IN TERMS OF OUR TECHNOLOGY FOR SETI?
A layman might wonder how a signal coming from four light-years away could be confused with noise being created right here inside of our own atmosphere. The Debrief asked Dr. Wright about the challenges involved in detecting such distinctions.
“Radio signals in space are fantastically weak, but our telescopes are fantastically sensitive,” he said. “They can in principle detect a cell phone on Mars. Indeed, this is why our deep space probes can ‘phone home’ with transmitters of just a few watts. Over interstellar distances they are even weaker, but can still be made out if enough power is put into them, say, a megawatt, equal to the power of a neighborhood of houses.”
It’s also not as if the possibility that this signal could be terrestrial in origin wasn’t being considered when it was first announced. Tessa Fisher, a PhD Student from the School of Earth and Space Exploration at Arizona State University, told The Debrief last year that the statistical likelihood of aliens wasn’t all that high.
“So, statistically, it’s probably not aliens, and some properties of the signal don’t fit what we’d expect from a signal produced by [an] intelligence,” she said. “It didn’t actually have any data encoded in it, for example. While it’s intriguing that it appears to come from the direction of Proxima Centauri…a week before this story came out, there was another research team that detected radio emissions that likely corresponded to Proxima Centauri experiencing massive solar flares.”
SO WAS THIS ALL JUST A HUGE WASTE OF TIME?
The scientists contacted by The Debrief and others involved in the project assure us that, rather than being a disappointment, this exercise represents a moment of opportunity to refine humanity’s abilities to detect a true extraterrestrial technosignature if and when one comes along. Dr. Wright described the ongoing process as a valuable “dry run” that will benefit the Breakthrough Listen team when future anomalous signals are detected.
“The team did lots of tests on the signal to try to prove it was from space, many of which they invented just for this signal,” he said. “Next time, they will be able to do those tests immediately, and rule out interference much faster.”
As to what the actual source of the signal once believed to originate from Proxima Centauri was, the jury is still out. Other scientists studying the data described the signal as ‘drifting in a way that is consistent with inexpensive crystal oscillators such as those commonly used in computers, phones, and radios.’ Analysis of historical data to identify the original source continues.
SO DOES THIS MEAN WE STILL MIGHT BE ALONE?
It’s probably hard for SETI enthusiasts to come away from this recent news without a bit of disappointment. The original discovery of the Proxima Centauri signal prompted a great deal of excitement for obvious reasons. If intelligent life were to show up orbiting our sun’s nearest stellar neighbor, that could suggest that such civilizations might be ubiquitous in our galaxy.
If, however, this signal turns out to simply be the result of a failing cell phone tower or some other mundane terrestrial artifact, we’re not left with many other promising prospects aside from the legendary “Wow! signal” of 1977. And even that one has recently been suggested to have come from a comet. So does this lack of technosignatures feed into the Fermi paradox? If alien intelligences are out there, why don’t we hear them? The Debrief asked Dr. Wright about this.
“I don’t think the non-detections put firm limits on the amount of technological life out there yet,” he said. “It could be abundant and just not transmitting. But it does mean that optimistic estimates of how many nearby species might be sending us powerful, always-on signals at the frequencies we’ve checked—we’ve ruled those out. On the other hand, there are still many more places to look and other frequencies to search! ”
And so, the search continues. Scientists like the ones we’ve spoken to are not giving up on the quest yet.
Follow and connect with author Jazz Shaw on Twitter:@JazzShaw