Radio burst pinpointed 3.6bn light-years away


Tuesday, 02 July, 2019



Radio burst pinpointed 3.6bn light-years away

An Australian-led international team of astronomers has determined the precise location of a powerful one-off burst of cosmic radio waves, thanks to CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia.

The galaxy from which the burst originated was subsequently imaged by three of the world’s largest optical telescopes — Keck, Gemini South and the European Southern Observatory’s Very Large — with the results published in the journal Science.

As noted by CSIRO’s Dr Keith Bannister, lead author on the study, “This is the big breakthrough that the field has been waiting for since astronomers discovered fast radio bursts in 2007.” In the 12 years since then, a global hunt has netted 85 of these bursts — most have been one-offs but a small fraction are ‘repeaters’ that recur in the same location.

In 2017 astronomers found a repeater’s home galaxy, but localising a one-off burst has been much more challenging. Fast radio bursts last less than a millisecond, making it difficult to accurately determine where they have come from.

That all changed when Dr Bannister’s team developed technology to freeze and save ASKAP data less than a second after a burst arrives at the telescope. This technology was used to pinpoint and map the location of FRB 180924 to the outskirts of its home galaxy (DES J214425.25−405400.81), located about 3.6 billion light-years away.

ASKAP is an array of multiple dish antennas and the burst had to travel a different distance to each dish, reaching them all at a slightly different time. Team member Dr Adam Deller, of Swinburne University of Technology, noted, “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 centre in the galactic suburbs.”

Dr Bannister added, “If we were to stand on the Moon and look down at the Earth with this precision, we would be able to tell not only which city the burst came from, but which postcode — and even which city block.”

Artist’s impression of CSIRO’s ASKAP radio telescope finding a fast radio burst and determining its precise location. The KECK, VLT and Gemini South optical telescopes joined ASKAP with follow-up observations to image the host galaxy. Image credit: CSIRO/Dr Andrew Howells.

To find out more about the home galaxy, the team imaged it with the European Southern Observatory’s 8 m Very Large Telescope in Chile and measured its distance with the 10 m Keck telescope in Hawaii and 8 m Gemini South telescope in Chile. Dr Deller noted that the one-off burst and its home galaxy look nothing like the previous identified repeater, which comes from a very tiny galaxy that is forming lots of stars.

“[The new burst] comes from a massive galaxy that is forming relatively few stars,” he said. “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.”

The cause of fast radio bursts remains unknown, but the ability to determine their exact location is a big leap towards solving this mystery.

“These bursts are altered by the matter they encounter in space,” said team member Dr Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR).

“Now we can pinpoint where they come from, we can use them to measure the amount of matter in intergalactic space.” This would reveal material that astronomers have struggled for decades to locate.

Top image caption: The Milky Way galaxy stretches above the core group of CSIRO’s ASKAP radio telescope. Image credit: CSIRO, Alex Cherney.

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