Two of the most extreme and mysterious objects in the universe might be sitting right next to each other. And they鈥檙e being flashy about it. New observations of the light from the only repeating fast radio burst we have seen show that it appears to be coming from a neutron star beside a huge black hole.
Fast radio bursts (FRBs) are powerful radio signals that flare from distant space for milliseconds and then disappear. Fewer than 30 of these bursts have ever been detected, but one appears to be special: FRB 121102 just keeps sending pulses of light our way.
Now, at the Netherlands Institute for Radio Astronomy and his colleagues have taken detailed measurements of the light from FRB 121102 and found a twist that indicates the source of the bursts is a small, fast-rotating object within an extreme magnetic field 鈥� like the ones around supermassive black holes.
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Starting on Christmas Day 2016 at Arecibo Observatory in Puerto Rico, Hessels and his team saw 16 new bursts from FRB 121102. They observed two more in August 2017 at the Green Bank Telescope in West Virginia. Some of these bursts were extremely short, lasting only a few tens of microseconds. The only thing in our universe we know of that rotates fast enough to beam light towards us and then away again so quickly is a neutron star.
They found that the radio waves were undergoing a process called Faraday rotation 鈥� where a strong magnetic field causes the direction of light鈥檚 polarisation to twist as it moves through the field.
Weird in two ways
Magnetic fields strong enough to cause this degree of Faraday rotation are rare. Hessels and his colleagues think that FRB 121102 may be next to a huge black hole, since black holes create the strongest magnetic fields in the universe. A black hole could also account for a weaker but constant radio signal that we see coming from near the FRB source.
FRB 121102鈥檚 uncommonly extreme environment and its strange repeating may be connected. 鈥淭he fact that it鈥檚 weird in those two ways hints at the idea that those two things have some sort of common origin,鈥� Hessels says.
Strong magnetic fields can also cause plasma lensing, in which highly magnetised material acts as a sort of magnifying glass for nearby light. This process could boost the light from the FRB and allow us to see bursts that would otherwise be too dim.
Although it鈥檚 the only repeating burst we鈥檝e seen, this magnification effect could mean that FRB 121102 isn鈥檛 so special after all. It could be that all fast radio bursts are repeaters but their light isn鈥檛 being boosted by lensing, so we only see the very brightest flash.
鈥淚t鈥檚 certainly a step, but whether it鈥檚 a step towards understanding this particular object or fast radio bursts in general still comes down to figuring out whether this one is unique or not,鈥� says at the University of Toronto in Canada.
In order to figure that out, we will have to dedicate more time to peering at other FRBs to see if they are repeating or experiencing Faraday rotation.
Read more: Is this ET? Mystery of strange radio bursts from space
Nature
