While mapping the universe for radio waves, researchers discovered a rare entity that discharges a massive burst of energy three times per hour, and it is unlike anything astronomers have ever observed.
This image shows the Milky Way as viewed from Earth. The star icon shows the position of the mysterious repeating transient. Image Credit: Dr. Natasha Hurley-Walker (ICRAR/Curtin).
The researchers assume it could be a white dwarf or a neutron star — collapsed cores of stars — with an ultra-robust magnetic field.
The strange object spins around in space and emits a ray of radiation that crosses our line of sight, and for a minute in every twenty, is one of the most vivid radio sources in the sky.
Astrophysicist, Dr. Natasha Hurley-Walker, from the Curtin University node of the International Centre for Radio Astronomy Research, headed the team that came across this unusual occurrence.
This object was appearing and disappearing over a few hours during our observations. That was completely unexpected. It was kind of spooky for an astronomer because there’s nothing known in the sky that does that. And it’s really quite close to us—about 4,000 lightyears away. It’s in our galactic backyard.
Dr. Natasha Hurley-Walker, Study Lead and Astrophysicist, ICRAR-Curtin University
The object was spotted by Curtin University Honors student Tyrone O’Doherty with the help of the Murchison Widefield Array (MWA) telescope in outback Western Australia and a new method that he had formulated.
“It’s exciting that the source I identified last year has turned out to be such a peculiar object,” said Mr. O’Doherty, who is currently pursuing a Ph.D. at Curtin.
“The MWA’s wide field of view and extreme sensitivity are perfect for surveying the entire sky and detecting the unexpected.”
Objects that switch on and off in the universe are not new to astronomers — they refer to them as “transients.”
When studying transients, you’re watching the death of a massive star or the activity of the remnants it leaves behind.
Dr. Gemma Anderson, Study Co-Author and Astrophysicist, ICRAR-Curtin University
“Slow transients” — like supernovae — tend to appear over a few days and vanish after a few months.
“Fast transients” — a type of neutron star known as a pulsar — turn on and off within milliseconds or seconds.
But Dr. Anderson said discovering something that turned on for a minute was very strange.
She said the strange object was extremely bright and smaller than the Sun, discharging highly-polarized radio waves — signifying the object had a very powerful magnetic field.
Dr. Hurley-Walker said the observations match a forecasted astrophysical object known as an “ultra-long period magnetar.”
It’s a type of slowly spinning neutron star that has been predicted to exist theoretically. But nobody expected to directly detect one like this because we didn’t expect them to be so bright. Somehow it’s converting magnetic energy to radio waves much more effectively than anything we’ve seen before.
Dr. Natasha Hurley-Walker, Study Lead and Astrophysicist, ICRAR-Curtin University
Dr. Hurley-Walker is currently tracking the object with the MWA to observe if it turns back on.
“If it does, there are telescopes across the Southern Hemisphere and even in orbit that can point straight to it,” she said.
Dr. Hurley-Walker aims to hunt for more of these rare objects in the huge archives of the MWA.
“More detections will tell astronomers whether this was a rare one-off event or a vast new population we’d never noticed before,” she said.
MWA Director Professor Steven Tingay said the telescope is a forerunner instrument for the Square Kilometer Array — an international initiative to construct the world’s largest radio telescopes in South Africa and Western Australia.
Key to finding this object, and studying its detailed properties, is the fact that we have been able to collect and store all the data the MWA produces for almost the last decade at the Pawsey Research Supercomputing Centre. Being able to look back through such a massive dataset when you find an object is pretty unique in astronomy.
Steven Tingay, Professor and Director, Murchison Radio-Astronomy Observatory
“There are, no doubt, many more gems to be discovered by the MWA and the SKA in coming years,” Tingay added.
The MWA is situated on the Murchison Radio-Astronomy Observatory in Western Australia. The observatory is run by CSIRO, Australia’s national science agency, and was set up with the support of the Australian and Western Australian Governments. The team acknowledges the Wajarri Yamatji as the traditional owners of the observatory site.
The Pawsey Supercomputing Research Centre in Perth – a Tier 1 publicly sponsored national supercomputing facility – helped store and process the MWA observations used in this study.
Shanghai Astronomical Observatory (SHAO) is a member of the MWA. China’s SKA Regional Centre Prototype, financially backed by the Ministry of Science and Technology of China and the Chinese Academy of Sciences, is hosted by SHAO and assisted in the processing of the MWA observations used in this study.
Repeating Transient Animation
An animation describing the discovery, the behavior of the object and what it might look like. Video Credit: ICRAR.
Journal Reference:
Hurley-Walker, N., et al. (2022) A radio transient with unusually slow periodic emission. Nature. doi.org/10.1038/s41586-021-04272-x.