Strange signals known as fast radio bursts (FRBs) are one of the most intriguing mysteries of modern astronomy, so the more of them we can locate, the closer we get to figuring what causes them. Now we're a step closer to solving the riddle, as astronomers have managed to trace an FRB back to its home galaxy, many billions of light-years away.
The name of the phenomenon is pretty self-explanatory: these strange signals are loud bursts of radio noise that flash up for mere milliseconds, then vanish. Because they're gone so quickly, it's been difficult for astronomers to pinpoint exactly where they're coming from, which is an important step towards deciphering their source.
This has only been done a handful of times. The latest detection comes from the Deep Synoptic Array-10 (DSA-10), an array of radio dishes in the Californian desert that's specifically designed for the task of identifying FRBs. On May 23 this year, it picked up a signal that's since come to be known as FRB 190523.
Using data gathered by DSA-10, the astronomers then used the Keck Observatory in Hawaii to trace the signal back to a galaxy about the same size and type as the Milky Way, some 7.9 billion light-years away.
While that might not tell us much on its own, the more of these signals that scientists can pinpoint, the more likely it'll be that a pattern will emerge. After all, Australian astronomers announced just a few weeks ago that they'd managed to pinpoint an FRB to a galaxy 3.9 billion light-years away. And this galaxy just so happens to be very similar to the one DSA-10 homed in on.
By contrast, the first-ever FRB to be localized – known as FRB121102 – was found to be coming from an active dwarf galaxy that's forming stars more than a hundred times faster than the Milky Way. This signal is also an oddity in other ways too – while the majority are one-and-done affairs, FRB121102 is the only known repeater, flaring up many times in an unpredictable pattern in the seven years since its discovery.
The fact that the repeater comes from an active galaxy, while two single FRBs have been traced to quieter galaxies, suggests that maybe the two types of signals come from completely different celestial objects, or form under different circumstances. For example magnetars – highly-active, magnetic neutron stars – have long been considered a contender, but this might not be the case for all signals.
"The theory that FRBs come from magnetars was developed in part because the earlier FRB 121102 came from an active star-forming environment, where young magnetars can be formed in the supernovae of massive stars," says Vikram Ravi, lead author of the study. "But the host galaxy of FRB 190523 is more mellow in comparison."
Ultimately, more data is needed to solve the mystery. And thankfully, both DSA-10 and the radio telescope array that the Australian team used, ASKAP, are only partway built at the moment. Both will feature many more radio dishes when they're finished, making them more efficient at scanning the skies.
The research was published in the journal Nature.
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