In a world first, an Australian-led international team of astronomers has determined the precise location of a powerful one-off burst of cosmic radio waves.
The massive release of energy came from a mysterious “fast radio burst” from more than three billion light years away.
“Where fast radio bursts come from, and what triggers them, has been an unsolved cosmic mystery since they were first detected more than a decade ago,” said Professor Elaine Sadler of the University of Sydney, a co-author of the study.
“Although we have now tracked one down to its parent galaxy, we still don’t know what event happened in that galaxy to trigger this powerful burst of energy.”
Fast radio bursts, as the name suggests, are detected as radio waves. The methodology developed by the Australian team allows for a rapid location of these events, allowing astronomers to quickly train optical telescopes on the bursts, providing vital new information.
The results are published today in Science.
“This is the big breakthrough that the field has been waiting for since astronomers discovered fast radio bursts in 2007,” CSIRO lead author Dr Keith Bannister said.
The discovery was made with CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope in Western Australia. The galaxy from which the burst originated was then imaged by three of the world’s largest optical telescopes.
In the 12 years since their discovery, a global hunt has netted just 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.
Dr Bannister’s team developed new technology to freeze and save ASKAP data less than a second after a burst arrives at the telescope.
This technology was used to pinpoint the location of FRB 180924 to its home galaxy. The team made a high-resolution map showing that the burst originated in the outskirts of a Milky Way-sized galaxy about 3.6 billion light-years away.
“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,” Dr Bannister said.
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.
“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,” team member Dr Adam Deller of Swinburne University of Technology said.
To find out more about the home galaxy, the team imaged it with the European Southern Observatory’s eight-metre Very Large Telescope in Chile and measured its distance with the 10-metre Keck telescope in Hawai’i and the eight-metre Gemini South telescope in Chile.
The cause of fast radio bursts remains unknown but the ability to determine their exact location is a big leap towards solving this mystery.
PhD candidate at the University of Sydney, Hao Qiu, assisted Dr Bannister build and test the detection software used to locate the fast radio burst.
“We expect this localisation to be the first of many. Now astronomers will be able to see a distribution of FRB host galaxies, which will help us interpret the environment where these bursts occur,” Mr Qiu said.
The localisation of the radio burst was done as part of a project using ASKAP called CRAFT (Commensal Real-time ASKAP Fast Transients) that is jointly led by Dr Bannister, Dr Jean-Pierre Macquart from Curtin University and Dr Ryan Shannon of Swinburne University of Technology.
Dr Shannon and CSIRO’s Dr Shivani Bhandari carried out the observations and were the first to spot the burst.
Stuart Ryder (Macquarie University), J. Xavier Prochaska (University of California Santa Cruz, USA) and Nicolas Tejos (Pontificia Universidad Catolica de Valparaiso, Chile) carried out the optical observations.
ASKAP is located at CSIRO’s Murchison Radio-astronomy Observatory (MRO) and is a precursor to the future Square Kilometre Array telescope.
The Wajarri Yamaji are the traditional owners of the Murchison site.
Hao Qiu receives a Hunstead Merit Scholarship and postgraduate scholarship. Keith Bannister (CSIRO), Jean-Pierre Macquart (Curtin/ICRAR) and Ryan Shannon (Swinburne) acknowledge Australian Research Council (ARC) grant DP180100857. Adam Deller (Swinburne) is the recipient of an ARC Future Fellowship (FT150100415). Stefan Osłowski (Swinburne) and Ryan Shannon (Swinburne) acknowledge support through ARC grant FL150100148. Ryan Shannon also acknowledges supportthrough ARC grant CE170100004. Nicolas Tejos (Chile) acknowledges support from PUCV research funding 039.333/2018. Work at the Naval Research Laboratory is supported by NASA.