Fast radio bursts (FRBs) are one of the most puzzling mysteries of the space age. These one-off, millisecond-long signals pour in from all corners of the cosmos, and so far nobody's been able to figure out what causes them or where they're even coming from. Now, a team of astronomers has finally managed to trace one of the signals back to its home galaxy billions of light-years away, meaning we're closing in on the culprit.
FRBs were first discovered in 2007, and since then 85 of them have been detected. These short, sharp bursts are easy to spot in data but hard to pin down, thanks to their transient nature. With no clear idea of where they're coming from, astronomers have had a tough time trying to figure what could be causing them. And while the majority are one-hit wonders, some repeat at irregular intervals, which only complicates things further.
But now, astronomers are reporting that they've finally managed to pinpoint where one of these signals has come from, with incredible precision. Normally the signal has come and gone long before astronomers can react, so the Australian science agency CSIRO developed new technology that can react in under a second when a telescope picks up a burst. This freezes and saves the telescope data as it was when the signal rolled in, which tells scientists where to point other instruments to investigate its origin.
In this first case, the story starts at the Australian Square Kilometer Array Pathfinder (ASKAP), a radio telescope in Western Australia, which detected a burst later named FRB 180924. Using the new method, the team managed to home in on where it came from – a Milky Way-sized galaxy called DES J214425.25−405400.81, located some 3.6 billion light-years away.
And not just the galaxy itself, either. The team could pinpoint precisely where in the galaxy it originated. That's because ASKAP is made up of an array of radio telescopes, and the team can measure when the signal washes over each unit, then use those time differences to triangulate the location.
"From these tiny time differences – just a fraction of a billionth of a second – we identified the burst's home galaxy and even its exact starting point, 13,000 light-years out from the galaxy's center in the galactic suburbs," says Adam Deller, a team member on the project.
With that cosmic pin dropped, the team then imaged the galaxy in closer detail to find out more about the environment there and look for clues as to what might be making the signals. The researchers did this using the Gemini South and Very Large Telescope in Chile, and the Keck Observatory in Hawaii.
Interestingly, the study found that the burst came from a massive galaxy that's no longer forming many new stars. That makes it a very different environment to the home galaxy of a "repeater" signal that was located in 2017.
"The burst we localized and its host galaxy look nothing like the 'repeater' and its host," says Deller. "This suggests that fast radio bursts can be produced in a variety of environments, or that the seemingly one-off bursts detected so far by ASKAP are generated by a different mechanism to the repeater."
While the mystery of the origin of FRBs remains unsolved for now, the ability to pinpoint their home galaxies is a huge step towards answering the question.
The research was published in the journal Science. The team describes the work in the video below.
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