The signals came from a red dwarf star – Ross 128 (GJ 447) – which is around 2,800 times dimmer than the Sun and is not yet known to have any planets, researchers said.
The “strange” radio signals were detected by astronomers at the University of Puerto Rico in May, using the Arecibo Observatory, which is a massive radio telescope built inside of a Puerto Rican sinkhole.
Abel Méndez, an astrobiologist at the University of Puerto Rico at Arecibo, said the star was observed for 10 minutes, during which time the signal was picked up and “almost periodic”.
Méndez said it’s extremely unlikely that intelligent extraterrestrial life is responsible, but noted the possibility can’t yet be ruled out.
While Arecibo is known for its role in efforts to search for signals from aliens, it’s also great for looking at distant galaxies and pinging near-Earth asteroids.
“In case you are wondering, the recurrent aliens hypothesis is at the bottom of many other better explanations,” Mendez told ‘Business Insider’.
Méndez thinks the signal is more likely from something humans put in space, perhaps a satellite that passed thousands of miles overhead.
“The field of view of [Arecibo] is wide enough, so there is the possibility that the signals were caused not by the star but another object in the line of sight,” Méndez said, adding that “some communication satellites transmit in the frequencies we observed.”
However, in a July 12 blog post about the mystery of Ross 128, he wrote that “we have never seen satellites emit bursts like that” and called the signals “very peculiar”.
Another possible explanation is a stellar flare, or outburst of energy from the star’s surface. Such bursts from the sun travel at light-speed, emit powerful radio signals, and can disrupt satellites and communications on Earth, as well as endanger astronauts.
Solar flares can also be chased by a slower-moving yet more energetic coronal mass ejections: a flood of solar particles that can distort our planet’s magnetic field, generate geomagnetic storms, and cripple power grids and fry electronics.
To see if the signals are still there, Méndez said Arecibo is going to stare down Ross 128 and its surroundings many more times, starting July 16.
“Success will be to find the signal again in the star but not in its surrounding[s]. If we don’t get the signal again then the mystery deepens, ” he said. “We are not sure if we can get to the bottom of this mystery from just the next observations if that was a rare event.”
But FAST isn’t operational right now, since it’s being calibrated, and Méndez said he doesn’t know when it will be back online.
Seth Shostak, a senior astronomer at the SETI Institute, confirmed that the group is “well aware of the signals” and might use its powerful Allen Telescope Array in California “to check them out.”
“The chances are high that they’re terrestrial interference, in fact. That’s really always been the case,” Shostak told Business Insider in an email.
Right now there’s really only one compelling signal from outer space that might come from aliens: “[T]he WOW signal,” Shostak said. “That one is still quite odd.”