Ask an astronomer what the top 10 unsolved mysteries in the universe are, and Fast Radio Bursts (FRBs) — intense bursts of radio emissions lasting mere milliseconds — would definitely figure on the list. The longstanding mystery of their origin, which is further compounded by the fact that less than two dozen such events have ever been detected, has spawned a plethora of scientific (and not so scientific) theories, including the occasional speculation that aliens are responsible for them.

Now, in a new study accepted for publication in the Astrophysical Journal Letters, two researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) have given the “aliens are behind it” hypothesis a slightly more scientific imprimatur. They argue that FRBs may be the result of “leakage” from planet-sized transmitters built by an extraterrestrial civilization to accelerate interstellar probes.

“We examine the possibility that FRBs originate from the activity of extragalactic civilizations. Our analysis shows that beams used for powering large light sails could yield parameters that are consistent with FRBs,” the researchers wrote in the study. “The characteristic diameter of the beam emitter is estimated through a combination of energetic and engineering constraints, and both approaches intriguingly yield a similar result which is on the scale of a large rocky planet.”

Basically, the authors of the study — Avi Loeb and Manasvi Lingam — state that the millisecondlong FRBs may be the result of a sufficiently advanced alien civilization trying to power spacecraft equipped with light sails (something that scientists have also thought about doing). To back their hypothesis, the researchers examined the feasibility of creating a radio transmitter strong enough for its emissions to be detectable across the immense distances FRBs have been seen coming from.

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They calculated that if the transmitter were solar-powered, and if it occupied an area twice the size of Earth, it could, in fact, generate the needed energy. In other words, while the construction of such transmitters is definitely a daunting task from an engineering and technological point of view, it is firmly within the realms of possibility that, say, an advanced Type I or Type II extraterrestrial civilization could build one. 

“To power a light sail, the transmitter would need to focus a beam on it continuously. Observers on Earth would see a brief flash because the sail and its host planet, star and galaxy are all moving relative to us,” CfA said in a statement released Thursday. “As a result, the beam sweeps across the sky and only points in our direction for a moment.”

Of course, the work is purely speculative in nature, and as any self-respecting astronomer would tell you, aliens should always be the last hypothesis one considers while attempting to explain an unknown occurrence — something that even the authors of the study acknowledge.

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“Science isn't a matter of belief, it's a matter of evidence,” Loeb said in the statement. “Deciding what’s likely ahead of time limits the possibilities. It's worth putting ideas out there and letting the data be the judge.”