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Australian telescope spies its first burst from beyond the galaxy, many more expected

The ASKAP telescope in Western Australia will collect the mysterious high energy signals known as fast radio bursts with unprecedented ease. Michael Lucy reports.

Some of the dishes of the ASKAP telescope.
Kim Steele

Astronomers using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in remote Western Australia have detected their first extragalactic “fast radio burst” (FRB).

Fast radio bursts are short, sharp spikes of radio waves that last only a few milliseconds and appear to come from unknown sources outside the Milky Way. The first FRB was discovered in 2007 – found by analysing data recorded at the Parkes radio telescope, in New South Wales, in 2001. Only two dozen or so have been found since.

The latest sighting, dubbed FRB170107 for the date on which it was discovered, was found by Keith Bannister and colleagues from Australia’s CSIRO and Curtin University and the International Centre for Radio Astronomy Research, as part of the Commensal Real-time ASKAP Fast Transients (CRAFT) survey.

The team set eight of ASKAP’s 36 dishes to watch a large patch of sky (about 1,000 times the area covered by the Moon) for FRBs. In less than four days they had a result. In the future they plan to use 12 dishes, and expect to find roughly one new burst every two days. At that rate it will take less than two months to double the total number of FRBs ever observed.

While the most exciting science from the CRAFT survey still lies ahead, FRB170107 provides some fascinating clues on its own.

What causes FRBs is something of a mystery. The signal looks like a single flash produced by a pulsar – a spinning neutron star emitting a sweeping beam of radiation that, somewhat like a lighthouse, from our point of view appears to blink on and off; but the lack of rapid repetition rules out a pulsar as the source. On the other hand, a couple of detected FRBs have repeated at irregular intervals, which also seems to rule out one-off events such as supernovas or stellar collisions as the source. No proposed explanation so far fits all the data.

The researchers estimate the source of FRB170107 to be some 7 billion light years away, and that in just over two and a half milliseconds it released as much energy as the Sun does in two and a half years. (A grain of salt: as Bannister notes via email, some of the assumptions behind these numbers “are pretty ropey”.)

The results are published in The Astrophysical Journal Letters.

Michael Lucy is the online editor of Cosmos.
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