Magnetars are a type of neutron stars, which are the collapsed cores of massive stars that have exploded as supernovae.
They are incredibly dense, with the mass of the sun squeezed into a sphere about 20 kilometres across.
Magnetars boast even stronger magnetic fields and can emit bursts of high-energy radiation, including X-rays and gamma rays.
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However, Dr Marcus Lower, a postdoctoral fellow at CSIRO, said the results measured on magnetar XTE J1810-197 were completely unexpected.
“Unlike the radio signals we’ve seen from other magnetars, this one is emitting enormous amounts of rapidly changing circular polarisation,” Dr Lower said. “We had never seen anything like this before.”
The study’s co-author, Dr Manisha Caleb from the University of Sydney, said studying magnetars offers insights into the physics of intense magnetic fields and the environments these create.
“The signals emitted from this magnetar imply that interactions at the surface of the star are more complex than previous theoretical explanations.”
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XTE J1810-197, the closest magnetar to Earth, is one of only a handful recorded producing radio pulses.
“Our results suggest there is a superheated plasma above the magnetar’s magnetic pole, which is acting like a polarising filter,” Dr Lower said.
“How exactly the plasma is doing this is still to be determined.”
XTE J1810-197 was first observed to emit radio signals in 2003 but went silent for over a decade.
The signals were again detected by the University of Manchester’s 76-m Lovell telescope at the Jodrell Bank Observatory in 2018 and followed up by teams using the Murriyang telescope in Parkes, NSW.
The telescope has been in operation for more than 60 years, but frequent updates mean it continues to make groundbreaking discoveries.
It’s one of four instruments comprising the Australia Telescope National Facility.
“With a diameter of 64 metres, Murriyang is one of the largest single-dish telescopes in the southern hemisphere dedicated to astronomy,” said CSIRO.
“It started operating in 1961, but only its basic structure has remained unchanged. The surface, control system, focus cabin, receivers, computers and cabling have all been upgraded – some parts many times – to keep the telescope at the cutting edge of radio astronomy.
“The telescope is now 10,000 times more sensitive than when it was first commissioned.”
It significantly includes an ultra-wide bandwidth receiver that allows for more precise measurements of celestial objects, especially magnetars. This receiver is highly sensitive to changes in brightness and polarisation across a broad range of radio frequencies.
“Studies of magnetars such as these provide insights into a range of extreme and unusual phenomena, such as plasma dynamics, bursts of X-rays and gamma-rays, and potentially fast radio bursts,” said CSIRO.
The spiral light discovered by researchers is not the first unusual pulse discovered by Australian teams.
Last year, a team at Curtin University discovered a mysterious pulsating stellar object that they believed could be an ultra-long-period magnetar.
Researchers made the discovery using the MWA telescope in Western Australia before it was subsequently corroborated by telescopes in South Africa and Spain, as well as the XMM-Newton telescope in space.
The apparent magnetar, now named GPM J1839−10, is 15,000 light-years away from Earth in the Scutum constellation.
Adam Thorn
Adam is a journalist who has worked for more than 40 prestigious media brands in the UK and Australia. Since 2005, his varied career has included stints as a reporter, copy editor, feature writer and editor for publications as diverse as Fleet Street newspaper The Sunday Times, fashion bible Jones, media and marketing website Mumbrella as well as lifestyle magazines such as GQ, Woman’s Weekly, Men’s Health and Loaded. He joined Momentum Media in early 2020 and currently writes for Australian Aviation and World of Aviation.
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