Fast radio bursts originating from outside the Milky Way were first detected almost 20 years ago. But what are they?
DR KATIE MACK (@AstroKatie) Katie is a theoretical astrophysicist. She currently holds the position of Hawking Chair in Cosmology and Science Communication at the Perimeter Institute for Theoretical Physics.
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You would think they would have been harder to miss: unimaginably powerful bursts of cosmic radiation, so bright they can blast our radio telescopes from billions of light-years away and occurring perhaps as often as a thousand times a day.
But fast radio bursts (FRBs) went undetected until 2007, and despite a decade and a half of investigation, remain one of the most enticing mysteries in astrophysics. Recent studies are providing new and promising hints about their origins, while at the same time illustrating why these cosmic firecrackers are so confounding in the first place.
When I first started hearing about FRBs in seminars, the big question wasn’t so much: “What astrophysical source is causing this?”, but rather: “Are we sure this isn’t just a blip in the machine?”
After all, whatever it was, it looked pretty suspicious. An FRB is a burst of radio radiation that lasts around a millisecond and spreads out in frequency in a way that looks an awful lot like a blip from a pulsar (a rapidly spinning core of a collapsed massive star, known as a neutron star, that’s left after a supernova explosion).
The thing is, FRBs don’t come from any known pulsar, don’t repeat like a pulsar and are apparently far more powerful than any pulsar pulse we’ve ever seen. To make matters worse, for years there was only one telescope – the Parkes Observatory in Australia – that had seen any FRBs at all. The debate got even more heated when it was discovered that some fraction of FRB-like bursts seen by Parkes were not from astronomical sources.
Called ‘perytons’, these bursts had always been suspected to be of terrestrial origin, but the case was closed after some clever detective work led by astronomer Dr Emily Petroff. She and her colleagues showed that perytons were strongly correlated with local lunchtime and were, in fact, radiation leakage from the observatory microwave when the door was opened too early. Could FRBs also be some kind of technological mistake?
It eventually became clear that FRBs are definitely coming from the distant Universe. More radio telescop
