29th January 2022
Astronomers discover mysterious new object in space
Astronomers at the International Centre for Radio Astronomy Research report the discovery of a repeating transient with an unusually slow spin, occurring just three times an hour. It is believed to be a new class of neutron star or white dwarf.
Credit: International Centre for Radio Astronomy Research
A team mapping radio waves in the Universe has discovered something highly unusual that releases a giant burst of energy three times an hour, and it’s unlike anything astronomers have seen before.
Located 4,000 light years away, the object has an ultra-powerful magnetic field. It sends out a beam of radiation that crosses our line of sight, and for a minute in every twenty, is one of the brightest radio sources in the sky.
“This object was appearing and disappearing over a few hours during our observations,” said Dr Natasha Hurley-Walker, astrophysicist at the International Centre for Radio Astronomy Research (ICRAR) in Australia, who led the team that made the discovery. “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 relatively close to us – about 4,000 light years away. It’s in our galactic backyard.”
The Milky Way as viewed from Earth. The star icon shows the position of the mysterious repeating transient. Credit: Dr Natasha Hurley-Walker (ICRAR/Curtin)
Curtin University Honours student, Tyrone O’Doherty, discovered the object using the Murchison Widefield Array (MWA) telescope in Western Australia alongside a new technique he developed.
“It’s exciting that the source I identified has turned out to be such a peculiar object,” said O’Doherty, who is now studying for a PhD 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 turn on and off in the Universe aren’t new to astronomers – they call them ‘transients’.
ICRAR-Curtin astrophysicist and study co-author Dr Gemma Anderson said that “when studying transients, you’re watching the death of a massive star or the activity of the remnants it leaves behind.”
‘Slow’ transients – like supernovae – might appear over the course of a few days and then disappear after a few months.
‘Fast’ transients – like a type of neutron star called a pulsar – flash on and off within milliseconds or seconds.
Finding something that turns on for a minute is therefore highly unusual. The mysterious object is extremely bright and smaller than the Sun, said Anderson – emitting highly-polarised radio waves – suggesting that it possesses an extremely strong magnetic field. The observations match a predicted astrophysical object called an ‘ultra-long period magnetar’.
“It’s a type of slowly spinning neutron star that has been predicted to exist theoretically,” said Hurley-Walker. “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.”
She plans to hunt for more of these strange objects in the vast 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.
The MWA is a precursor instrument for the massive Square Kilometre Array (SKA) – a global initiative to build the world’s largest ever radio telescopes in both Western Australia and South Africa, scheduled for first light in 2027.
“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,” said Professor Steven Tingay, Director of the MWA. “Being able to look back through such a massive dataset when you find an object is pretty unique in astronomy. There are, no doubt, many more gems to be discovered by the MWA and the SKA in the coming years.”
Dr Hurley-Walker and her colleagues have published their study this week in the peer-reviewed journal Nature.
The Pawsey Supercomputing Research Centre, which stored and shared the data used by this project. Credit: Pawsey Supercomputing Research Centre
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