Mysterious radio signals from space

What are these strange messages, and should we be using the A- Word!?
15 January 2019

Interview with 

Fran Day, University of Cambridge




There have been recent reports of a mysterious repeating radio signal coming from a distant galaxy one and a half billion light years away. What are these strange messages, and should we be using the A- Word!? Astrophysicist Fran Day, from the University of Cambridge, has been looking at the papers describing the phenomenon for Georgia Mills and Chris Smith. Starting with, what exactly is this signal? 

Fran - This is fast radio bursts, which do exactly what they say on the tin. They’re bursts of radio waves, which have been observed all across the sky. They were first discovered in 2007 and we don't know where they come from. So they really are mysterious. The exciting thing about this result is that they've discovered 13 new fast radio bursts and one of them is a repeating fast radio burst.

Georgia - And what does that mean, "repeating"?

Fran - This means that when we look at one point in the sky we see it do a radio burst several times.

Georgia - Right. And is it the same sort of pattern going ahead again and again?

Fran - It’s quite irregular. So they vary on the order of days to months. There'd be like a few in a day and then there was one that was like a month later or something. And there's only been one other repeating fast radio burst ever discovered. All the rest, we see one burst and then we never see anything from that patch of sky again. So this is quite a big clue to their origin that there's now two of these repeaters.

Georgia - Do we have any ideas what might have caused these?

Fran - We don't know is the short answer, but scientists have an awful lot of theories. So among astrophysicists some of the more popular theories are that they might be collisions between black holes or neutron stars. They have an awful lot of energy. A fast radio burst has as much energy in a millisecond as the sun produces in 80 years. So they need to be very energetic objects. They could also be especially energetic supernova, which is the explosion at the end of a star's life. There are also more exotic theories, for example in some theories of dark matter you can get a dark matter induced collapse of a neutron star that would lead to a big radio burst. And of course occasionally people suggest that they're aliens. But I think at the moment there isn’t evidence for this.

Georgia - I knew it. I knew it would be too good to be true. How did we find them?

Fran - They're observed using a radio telescope. So the latest result is from the CHIME Radio Telescope, which stands for the Canada Hydrogen Intensity Mapping Experiment. So this is a new telescope, it just went online in March, and it's already obviously discovered huge results.

Georgia - And is it a matter of being in the right place at the right time or do you think we're going to see more and more of these now?

Fran - I think we'll see more and more. CHIME has a very large field of view, it looks across a lot of the sky at once, and it has very good amplifiers, which makes it very good at searching for fast radio bursts. So now we've got this up and running. I think we’re likely to see more discoveries from CHIME.

Chris - And, Fran, does the fact that you've got one that keeps coming back, does that mean that we can now use that to try and study what these things are because we can look at what is in that patch of space using a range of different techniques to see what else is there and that will then hopefully see what the source of the fast radio repeat burst is?

Fran - Hopefully. We don't know whether the repeaters are the same thing as the isolated fast radio bursts. It might be that they're entirely different objects. But certainly a good next step is to look very carefully at the patches of space where we know we've seen fast radio bursts to see if there are signals in other wavelengths...


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