In August, Russian astronomers announced that they had detected a blast of radio waves coming from the direction of the star HD164595, 94 light years away. Maybe, they said, the blast came from aliens in orbit. Headlines breathlessly speculated about extraterrestrials, and other telescopes around the world swung to look at the same star, trying to catch the signal.
But these scientists had actually picked the radio waves up in May 2015---they had just kept it quiet for more than a year. Partly because of that delay, other astronomers were unable to distinguish between possibilities mundane and spectacular. Had a hypothetical extraterrestrial broadcast gone offline, or was the signal a fluke---some spike from inside the Russian observatory itself, or a satellite passing overhead (most likely)?
SETI as a field has ways to combat these ambiguities---so that if scientists find a candidate extraterrestrial signal, they will be able to identify it right away and rule out terrestrial interference. But the world’s newest and best-heeled SETI search, the Breakthrough Listen project, may be vulnerable to the some of the same problems the Russian scientists faced.
In the world of alien hunting, scientists don’t take candidate signals seriously until they see them more than once, with multiple telescopes. SETI programs detect seemingly-intelligent-in-origin blips all the time, and they often originate from our technology. A huge part of SETI science is distinguishing between, say, a prematurely opened microwave and the Encyclopedia Galactica via the planet Endorp. And the best ways to do that are real-time processing (or at least close to it) and timely confirmation from other telescopes---aspects of the Breakthrough search that have room for improvement.
In July 2015, an organization called Breakthrough Initiatives---on whose board sit Russian billionaire Yuri Milner, physicist Stephen Hawking, and Mark Zuckerberg---made a big announcement: The organization was starting a $100 million search for extraterrestrial intelligence, called Breakthrough Listen.
The program began collecting data with the Green Bank Telescope in West Virginia last year. In October, the team announced they will collaborate with the 500-meter FAST telescope in China, and earlier this month, Breakthrough began observations with the Parkes Radio Telescope in Australia. Within their observations, says astronomer Dan Werthimer, a lead Breakthrough scientist, “we look for a rich variety of signal types, because it’s very hard to know what ET might be doing.” But the way the project currently processes those signals---with a lag between observation and analysis---means they won’t necessarily be able to verify an intelligent extraterrestrial signal if they catch one.
To find signals, the team puts some data out to the public, on its SETI@Home platform and raw on their website. The majority, though, stays with the scientists, for expert algorithmic analysis and a human look. Soon, the team expects to identify potential pings a week after the telescopes actually pick them up. That gap, though it sounds small, still poses a problem: No one---neither the original finders nor the would-be confirmers---will be able to follow up fast, when the signal, be it alien or human, is most likely to persist.
“The eventual goal is to actually find something in near real-time,” says Werthimer. And that’s the scale on which scientists have done much of the previous SETI research, although admittedly the Breakthrough Listen team gathers more data per second than any previous project, making the task more daunting.
But right now, their team is just beginning to develop their data-analysis pipeline, according to Werthimer. And only a small fraction of the many months of data has been fully scrutinized so far.
That lag between surveillance and study could set the project up to miss signals. “Our philosophy has been that it’s important to look back quickly,” says Jill Tarter, the former head of NASA’s only SETI program, the High-Resolution Microwave Survey, and the SETI Institute’s alien searches. Previous projects, and modern ones like the search at the Allen Telescope Array and METI International’s hunt for laser pulses, process their data in real-time. At the Allen Array, within a few minutes of picking up radio waves, software combs them for signs of significance. If it finds something interesting, the telescope swings back right away to see if the strange thing is still there. After more automated verification tests, the computers alert the humans, right away. The humans take a look, and then, depending, call other humans with telescopes, also right away.
But right now, if Breakthrough finds a candidate signal, it might sit on a disk, unidentified, for months. As in the HD164595 debacle, no one will be able to confirm its origin or existence in a timely way, because no one---including the Breakthrough team---will know it exists at all.
If they processed in near-real-time, as they plan to, their telescopes would get an alert almost as soon they detected something interesting, and then the system would go look for that something again. Right now, they can look back only much later.
Unlike the Russian scientists, Breakthrough's astronomers are unlikely to announce that weird radio waves they see only once might be aliens. But they are also less likely than fast follow-uppers to see those weird radio waves more than once, and learn more about them. So although they’re not likely to make big news by announcing false positives, they might miss actual signals, from actual aliens.
Most false positives are just human technology---airport radar, too-close cell phones, spook satellites---masquerading as extraterrestrial messages. And Breakthrough could improve the tools they use to unmask those masqueraders. First, by fixing the real-time problem. But also by adding antennas. Breakthrough currently does its observations using just one radio antenna at a time (Parkes, Green Bank, and FAST are all single-dish radio telescopes). “They ought to be thinking about what other telescope they can use,” says Tarter.
The best way to tell if your telescope is picking up an alien signal or one from humans is to get independent verification. If a second telescope in different location watches the same spot in sky simultaneously, it won’t pick up the same earthly interference. So if astronomers see a suspicious signal with one telescope and not the other, they can tell it comes from Earth and not from ET. It’s like how an airplane passing over Orion from my perspective won’t appear at all in your view of the constellation.
In all of its campaigns, the SETI Institute’s Project Phoenix used a “Follow-Up Detection Device,” hooked up to a second, far-off telescope (in the movie Contact, Jodie Foster kisses her computer screen and says, “Thank you, Elmer,” as in “FUDD”). And one day when their second telescope was broken, they learned how important it actually was. False alarm bells rang hard, and radio waves from the definitely-from-people Solar and Heliospheric Observatory almost had them thinking about breaking out the champagne to toast an end to our cosmic loneliness.
Werthimer agrees that using two telescopes is a smart method to rule out interference. “That’s a good way to do it,” he says. “It’s kind of an expensive way to do it.” Which is true---they would have to commandeer other telescopes and build new instrumentation. But Breakthrough Listen also has more money than any other SETI scientists.
Werthimer says Breakthrough is hoping to do experiments using array telescopes, like South Africa’s MeerKAT, whose many antennas could accomplish a similar sifting of signals. And, he continues, Parkes---although it has just one antenna---has an instrument that can look at 13 spots on the sky at once. They can rule out signals that seem to come from multiple spots, which is what they would see if, say, the telescope was actually picking up a nearby television station.
But although that many-eyed instrument exists, the team isn’t actually using it yet. In their Green Bank observations, Breakthrough tries to do the job two telescopes would using a technique called nodding. “We point the telescope at some star, and then we move away from that star maybe five minutes later to a different star, and then we move back to Star A and back to B, A, B,” says Werthimer. “What we expect is that ET would only be at A. We would find the same signal all three times at A and never at B on the sky.”
It’s a start. But our technology bursts on and off at all kinds of intervals, Tarter points out, showing up one second and not the next, or staying on for an hour and then dipping out. If a signal appears when you’re looking at Star A and disappears when you look away, that could mean it comes from Star A. Or an infringing digital camera could have turned off at the same time you moved the telescope. A coincidence like that is unlikely to happen multiple times in a row, but it could.
Breakthrough Listen’s projected funding represents the most money (Milner’s) that any private enterprise has ever committed to an individual SETI project in Earth’s history, and the team is tasked with trying to answer one of our biggest collective questions: Are we alone? “I wish they were spending more time thinking about how to optimize what they have,” says Tarter. “And they’ll get there.”
Getting there is hard and complicated. But it is at least straightforward. If Breakthrough Listen speeds up its signal-detection and marshals more telescopic resources, it could cut down on false positives, unverifiable question-marks, and missed opportunities. Just ask the Russians.
