It’s a bold claim. Two astronomers think they have spotted messages from not just one extraterrestrial civilisation, but 234 of them. The news has sparked a lively debate in the field as other astronomers think the claim is premature and are working fast to get to the bottom of the signals.
In 2012, Ermanno Borra at Laval University in Quebec suggested that an extraterrestrial civilisation might use a laser as a means of interstellar communication. If the little green men simply flashed a laser toward the Earth like a strobe light, we would see periodic bursts of light hidden in the spectrum of their host star. They would be incredibly faint and rapid, but a mathematical analysis could uncover them.
“The kind of energy needed to generate this signal is not crazy,” says Borra. In fact, Borra showed that technology we have on Earth today – specifically the Helios laser at the Lawrence Livermore National Laboratory – could generate that kind of signal, should we want to reveal ourselves to the cosmos.
With this in mind, Borra’s graduate student Eric Trottier combed through 2.5 million stars recorded by the Sloan Digital Sky Survey in search of such a signal. He found it, down to the exact shape, in 234 stars.
The overwhelming majority of those stars are in the same spectral class as the sun, which Borra says supports his hypothesis that this signature must be the result of extraterrestrial intelligent life. And with the data in hand, he thinks that 234 distinct civilisations are beaming pulses of the same periodicity (roughly 1.65 picoseconds) toward the Earth.
Borra and Trottier ruled out other possible explanations for the pattern, like rapid pulsations in the atmospheres of the stars themselves and rotational transitions in molecules. “We have to follow a scientific approach, not an emotional one,” says Borra. “But intuitively – my emotion speaks now – I strongly suspect that it’s an ETI signal.”
Other astronomers think that Borra’s intuition might have run away with him.
“They don’t consider every natural possibility and jump prematurely to the supernatural – so to speak – conclusion,” says Peter Plavchan at Missouri State University in Springfield. “I think it’s way too premature to do that.”
“There is perhaps no bolder claim that one could make in observational astrophysics than the discovery of intelligent life beyond the Earth,” says Andrew Siemion, the director of the SETI Research Centre at the University of California Berkeley. “It’s an incredibly profound subject—and of course that’s why many of us devote our lives to the field and put so much energy into trying to answer these questions. But you can’t make such definitive statements about detections unless you’ve exhausted every possible means of follow-up.”
So that’s exactly what the Breakthrough Listen Initiative—a project headed by Siemion that searches for signs of intelligent life beyond Earth—will do. The team plans to observe several stars from Borra’s sample with the 2.4-meter Automated Planet Finder telescope at the Lick Observatory in California.
Borra is excited to see that others are taking the reins. “At this stage, the signal is so strange, that although our detailed analysis seems to indicate that it is a real signal, it has to be validated with more work,” he says.
Still, the Breakthrough Listen team doesn’t share Borra’s enthusiasm. According to a statement, they have rated the detection as a zero to 1 on the Rio Scale for SETI observations, meaning that it is insignificant.
In fact, Siemion thinks the spectral patterns were likely caused by errors in calibration or data analysis. And Plavchan agrees. He points to several steps in the team’s data analysis that “scared him” because they didn’t consider how those steps might affect their results—a red flag in any scientific claim. At the end of the day, the signal probably comes down to a human error, he says.
“It’s not a bad idea to look for a signal, it’s just that they didn’t do their homework,” says Plavchan.