Based on breathless news reports from many prominent media outlets that should know better, this week’s biggest non-story in science is the discovery of a possible radio signal from talkative aliens elsewhere in the Milky Way. I’m here to tell you, alas, that anyone hoping for this to be the moment of First Contact with another galactic civilization is very likely to be disappointed.
It all started innocently enough, with a carefully worded blog post this past Saturday from the respected science journalist Paul Gilster. Gilster wrote about a message he had received from some SETI (Search for Extraterrestrial Intelligence) researchers who reported a curiously powerful 3-second burst of radio waves from a star less than 100 light-years away. The researchers, led by Nikolai Bursov of the Russian Academy of Sciences, couldn't rule out the possibility that the signal was artificial, and were intrigued enough that they called for “permanent monitoring” of the star.
Gilster’s post ignited a firestorm of sensationalistic and credulous news coverage that is still blazing as I write this, burning through newspapers and websites to astound most everyone who encounters it. Soon, I predict, it will burn out—as these sorts of stories (almost) always do.
Here's what happened: in May of 2015, the RATAN-600 radio telescope in Zelenchukskaya, Russia detected the signal from the direction of HD 164595, a star about 94 light-years away in the constellation Hercules. This is a star very much like our Sun albeit slightly older, with an estimated age of 6.3 billion years. It also harbors at least one known planet, an uninhabitable Neptune-sized world, though of course others more habitable could exist in the system.
If the signal really is artificial, and really does come from HD 164595, its energy source must be gargantuan. According to Seth Shostak, an astronomer at the SETI Institute in California who was not involved with the research, a radio blast sent out in all directions by a hypothetical alien civilization would take hundreds of times more power than that of all the sunlight bathing the Earth, based on how bright the signal appeared in the Russian telescope (that's because we'd only be seeing a tiny part of of the total radio energy).
If it were instead a beam focused solely on the Earth, the signal would still require twice the electricity used by the United States in an entire year. Clearly, if this is another galactic civilization, they are far, far more advanced than our own.
The trouble is, there is no good reason to think that this signal is due to aliens at all—and there never was, according to Eric Korpela, an astronomer at the University of California in Berkeley. Korpela heads SETI@Home, a citizen-science initiative that processes SETI data using home computers; on the SETI@Home blog, Korpela said that after evaluating the available evidence he was “unimpressed” and that the data was “relatively uninteresting.”
“SETI@home has seen millions of potential signals with similar characteristics, but it takes more than that to make a good candidate,” Korpela continued. “Multiple detections are a minimum criterion.”
That's not what the Russian telescope found. The putative signal only occurred once out of 39 times the RATAN-600 telescope scanned the star, and the scans themselves were performed in such a way that many potential false positives could not be ruled out. Rather than being a beacon from ET, Korpela said, the signal could just as easily have been due to flares from the target star, the burp of a supermassive black hole in a background galaxy, or even the chance magnification of ordinary, all-natural stellar radio emissions by a passing foreground star or a transient ripple of interstellar plasma.
What this boils down to is that extraordinary claims require extraordinary evidence—evidence that can be very hard to come by for modern SETI programs. Contrary to Hollywood depictions, SETI efforts tend to have meager budgets that only support infrequent observations of small fractions of the sky in narrow bandwidth ranges. Could the new signal from HD 164595 be a genuine transmission from a cosmic civilization? Well, yes, conceivably it could. But so could the millions of other curious optical blips and radio spikes sitting in SETI archives, each a singular phenomenon that whispered just once into a telescope, never to repeat or return. This has happened before—see, for instance, the tantalizing “Wow! signal” from 1977, and the resulting decades of fruitless efforts see it a second time.
Even assuming there was enough telescope time available (there isn’t), every SETI program on Earth would likely go bankrupt trying to follow-up each of the millions of potential candidates if each received the care and attention bestowed upon the Wow! signal. In such a resource-constrained environment, only the very best and most compelling signals should merit much closer attention—and Korpela isn’t sure the signal from HD 164595 has crossed that threshold.
The real problem, Korpela goes on, is that the media frenzy over HD 164595 means that no reputable SETI program can now afford to not use precious telescope time to look for other signals from HD 164595. These projects need money, and they need public attention—ignoring the signal even if it is overwhelmingly likely to prove spurious is not an option. “We’ll be along for the ride,” he wrote. “And we’ll all find nothing.”
Indeed, according to Shostak, the SETI Institute’s Allen Telescope Array is already looking at the star, though so far they have yet to see anything peculiar. Other results are now coming in. Just this morning the Breakthrough Listen project, a private SETI endeavor funded by the billionaire Yuri Milner, released results of a follow-up on HD 164595 using archival data as well as new observations from the Green Bank Telescope in West Virginia. Breakthrough found—you guessed it—nothing.
More curiously, Breakthrough’s statistical analysis of the available data suggests that, if produced by natural astrophysical causes, one would expect that previous surveys would have seen such strong signals elsewhere in the sky. Which means that the RATAN-600 team was “either extremely lucky to detect this source in their observations, or that the transient is due to local interference or other calibration issues.” That is, absent the possibility of aliens, even an astrophysical source for the signal looks suspect—a far more likely explanation for the signal would be the passage of a satellite overhead, or an errant signal from electric currents coursing through wires within the observatory itself, or even a software glitch.
Nevertheless, the Breakthrough Listen team intends to periodically revisit HD 164595 in the future to keep looking for a repetition of the signal. Other SETI programs will undoubtedly do the same. And perhaps they should. But let’s not fool ourselves: Even in the lofty, noble quest to break our cosmic solitude, sometimes the tail can wag the dog.
Now if you’re interested in a truly epochal discovery relevant to the search for extraterrestrial life, I would refer you to last week’s announcement of a rocky planet found in a habitable orbit around the Sun’s nearest neighboring star, Proxima Centauri—which frustratingly seems to have made less of an impression than this week’s far more questionable news.