Energy flashes in distant galaxies 'could be proof of aliens'

Flashes of energy detected in distant galaxies could be evidence of aliens powering interstellar spacecraft, according to scientists at Harvard University.

Discovered in 2007, Fast Radio Bursts (FRBs) are intense radio pulses lasting up to a millisecond.

Their origins remain unknown, and fewer than two dozen have been detected by the world's largest radio telescopes - but they appear to occur in remote galaxies billions of light years away.

Now, a team from Harvard has suggested FRBs could be leaked energy from powerful transmitters built in order to send giant light sail ships on interstellar voyages.

A light sail uses the tiny amount of pressure exerted by light to produce a small but constant acceleration which allows a spacecraft to reach a great speed.

Professor Avi Loeb, from the Harvard-Smithsonian Centre for Astrophysics, said: "Fast radio bursts 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."

Professor Loeb, along with fellow Harvard colleague Dr Manasvi Lingham, has studied the feasibility of building a radio transmitter powerful enough to be detectable from such a large distance.

They concluded a solar-powered system would need to use an area twice the size of Earth to capture enough of the sun's rays to create the required energy.

They also said water-cooling on a massive scale would be needed to stop the underlying structure from melting.

The energy levels responsible for FRBs would be enough to push a payload weighing a million tons - about 20 times the mass of the largest cruise ships on Earth.

Professor Lingham said: "That's big enough to carry living passengers across interstellar or even intergalactic distances."

Writing in the journal Astrophysical Journal Letters, the scientists said the fact FRBs have made repeat appearances that cannot be explained by cataclysmic natural events could be a clue to their artificial origin.

They also explained FRBs are only observed as brief flashes on Earth because the sail and its host planet, star and galaxy are all moving relative to Earth.

As a result, the beam sweeps across the sky and only points towards us for a split second.

Professor Loeb added: "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."