Fast radio bursts: Are aliens sending us messages from light years away?

Wherever they are coming from is likely to be an extreme and spectacular place

Scientists have picked up blasts of radio signals coming from deep in space. And whatever they are, they are very intriguing indeed.

The bursts are coming from some deep, extreme and bizarre place many light years away. But much still remains to be learnt about their unusual source.

Scientists have been monitoring the blasts – known as fast radio bursts – in recent years, though they are not much closer to understanding their origin. The latest breakthrough is one of the biggest: it is the second ever time that scientists have picked up a repeating signal, as well as adding 13 new examples to the 60 we know about.

What are fast radio bursts?

Very short, very intense stabs of radio energy being blasted through space. They last only for a few miliseconds, but in that tiny bit of time they pack in the amount of energy it takes 12 months for the Sun to produce.

The blast of energy is constant through that very short period, and at different frequencies.

Where are they coming from?

Nobody really knows, for certain. These mysterious blasts are unknown in origin – they are coming from the depths of space, billions of light years away, rather than our own galaxy – but beyond that little is known about what their origin might be.

In another way, they come from everywhere: blasting at us all from all over the sky. The newest blasts are remarkable in part because they're only the second time we've picked up a repeating one – for the most part, they come from different places, meaning that scientists have to scan the entire sky in the hope of seeing them.

Are they being sent by aliens?

Some people think so, or at least that we should take the possibility seriously. Avi Loeb, from the Harvard-Smithsonian Centre for Astrophysics, has suggested that humanity needs to take seriously the possibility it is receiving messages from extraterrestrial civilisations.

“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,” Loeb has said. “An artificial origin is worth contemplating and checking.”

If that is the case, then the civilisation flinging the blasts towards us is likely to be nothing like our own – among other things, it would have to have built a planet-sized transmitter in order to pelt the messages across the galaxies and towards us. But while that's beyond our own capabilities, it's not beyond the realm of physical possibility and so presumably could be developed by a sufficiently advanced civilisation, Professor Loeb has argued.

It isn't necessarily the case that the blasts are messages being sent by those aliens, even if there are extraterrestrials on the other end. Instead, we could be picking up stray blasts that are being used to push huge spaceships across the universe, he wrote in 2017 – the intense blast of energy we experience is powerful enough to carry vast ships over even more vast differences.

If that's happening, the transmitter would have to be pointing its beam at wherever the ship was in space – since the ship, the transmitter, and its destination would be continually moving, sometimes it would miss, and when that happens the blasts might leak through and hit us. That would explain some of the most intriguing parts of the FRBs, such as the fact they appear to come at us with no real pattern and from various points in the sky.

What else might they be?

Many other scientists aren't quite as taken by the idea the bursts are coming from an alien civilisation. But the fact remains that whatever is generating such intense spurts of radio waves and throwing them across the universe must be very extreme and very strange, and probably unlike anything we have ever seen before: it must be relatively small, and very energetic.

They could, for instance, be getting thrown out by a type of neutron star known as a magnetar – a small but very intense star. Others have suggested they could be the result of a star falling into a black hole, destabilising as it gets torn up and throwing out the quick blasts.

Scientists hope that as more of the FRBs are found, they can learn more about their qualities and try and understand more about the origin. But for now it remains a source of intense dispute and mystery.