Fast radio bursts (FRBs) — powerful radio flashes lasting just milliseconds, with mysterious origins that continue to be a matter of debate — could be evidence of advanced alien technology, new research from Harvard suggests. Specifically, FRBs might be leakage from transmitters powering giant light sail probes in galaxies other than our own.

FRBs are mysterious and rarely detected bursts of radio emission that have durations of milliseconds and exhibit the characteristic dispersion sweep of radio pulsars.

These events emit as much energy in one millisecond as the Sun emits in 10,000 years, but the physical phenomenon that causes them is unknown.

The first FRB was discovered in 2007, although it was actually observed some six years earlier, in archival data from a pulsar survey of the Magellanic Clouds.

Only 18 FRBs have been detected to date. Most give off only a single burst and do not flash repeatedly.

They are inferred to originate from distant galaxies, billions of light-years away.

Avi Loeb, the Chair of the Astronomy Department and the Frank B. Baird Jr. Professor of Science at Harvard University, and his colleague at Harvard, Manasvi Lingam, examined the feasibility of creating a radio transmitter strong enough for it to be detectable across such immense distances.

The team found that, if the transmitter were solar powered, the sunlight falling on an area of an exoplanet twice the size of the Earth would be enough to generate the needed energy.

Such a vast construction project is well beyond our technology, but within the realm of possibility according to the laws of physics.

The researchers also considered whether such a transmitter would be viable from an engineering perspective, or whether the tremendous energies involved would melt any underlying structure.

Again, they found that a water-cooled device twice the size of Earth could withstand the heat.

They then asked, why build such an instrument in the first place?

They argue that the most plausible use of such power is driving interstellar light sails.

The amount of power involved would be sufficient to push a payload of a million tons, or about 20 times the largest cruise ships on Earth.

“That’s big enough to carry living passengers across interstellar or even intergalactic distances,” Dr. Lingam said.

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.

As a result, the beam sweeps across the sky and only points in our direction for a moment.

Repeated appearances of the beam, which were observed but cannot be explained by cataclysmic astrophysical events, might provide important clues about its artificial origin.

“FRBs are exceedingly bright given their short duration and origin at great distances, and we haven’t identified a possible natural source with any confidence. An artificial origin is worth contemplating and checking,” said Prof. Loeb, who also chairs the Advisory Committee for the Breakthrough Starshot Initiative and serves as the Science Theory Director for all Initiatives of the Breakthrough Prize Foundation.

He admits that this work is speculative. When asked whether he really believes that any fast radio bursts are due to aliens, he replied, “Science isn’t a matter of belief, it’s a matter of evidence. Deciding what’s likely ahead of time limits the possibilities. It’s worth putting ideas out there and letting the data be the judge.”

The paper reporting this work has been accepted for publication in the Astrophysical Journal Letters, but has been published on arXiv.org ahead of time.

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Manasvi Lingam & Abraham Loeb. 2017. Fast Radio Bursts from Extragalactic Light Sails. ApJL, in press; arXiv: 1701.01109

This article is based on a press-release from the Harvard-Smithsonian Center for Astrophysics.