An international team led by astronomers from the Curtin University node of the International Center for Radio Astronomy Research (ICRAR) has discovered a new type of stellar object that challenges our understanding of neutron star physics.
The object could be a very tall magnetar, which is a rare type of star with extremely strong magnetic fields that can produce powerful bursts of energy.
Until recently, all known magnetars released energy at intervals of a few seconds to a few minutes. The newly discovered object emits radio waves every 22 minutes, making it the longest magnetic period ever discovered. Publication of the research in the journal nature.
Astronomers discovered the object using the Murchison Widefield Array (MWA), a radio telescope in Wajarri Yamaji Country in remote Western Australia. The magnetar, named GPM J1839−10, is 15,000 light-years from Earth in the constellation of Scutum, said lead author Dr. Natasha Hurley-Walker.
“This remarkable object challenges our understanding of neutron stars and magnetars, which are some of the most exotic and extreme objects in the universe,” she said.
The stellar body is only the second of its kind ever discovered after the discovery of the first by undergraduate student Tyrone O’Doherty at Curtin University.
At first, scientists were unable to explain what they had found. They published a paper in nature in January 2022 describes a mysterious transient object that appears and disappears sporadically, emitting powerful beams of energy three times an hour.
The first thing surprised us, said Dr Hurley Walker – O’Doherty’s honorary supervisor -.
“We were baffled,” she said. “So we started looking for similar objects to see if it was an isolated event or just the tip of the iceberg.”
Between July and September 2022, the team surveyed the sky with the MWA telescope. And they quickly found what they were looking for in GPM J1839−10. It emits bursts of energy that last up to five minutes – five times longer than the first object.
Other telescopes followed to confirm the discovery and learn more about the object’s unique properties.
Three included CSIRO Radio Telescopes in Australia, the MeerKAT Radio Telescope in South Africa, the Grantecan (GTC) 10m Telescope, and the XMM-Newton Space Telescope.
Armed with the celestial coordinates and their characteristics of GPM J1839−10, the team also began searching the observation archives of the world’s leading radio telescopes.
“It appeared in observations by the Giant Metrewave Radio Telescope (GMRT) in India, and the Very Large Array (VLA) in the US had observations going back to 1988,” she said.
“That was an amazing moment for me. I was five years old when our telescopes first recorded pulses from this object, but it went unnoticed, and it remained hidden in the data for 33 years.
“They missed it because they didn’t expect to find anything like it.”
Not all magnetars produce radio waves. Some are below the “death line,” a critical threshold at which a star’s magnetic field becomes too weak to generate high-energy emissions.
“The object we detected is rotating very slowly to produce radio waves – it is below the death line,” said Dr. Hurley-Walker.
“Assuming it’s a magnetar, it shouldn’t be possible for this object to produce radio waves. But we do see it. And we’re not just talking about a small flash of radio emission. Every 22 minutes, it emits a pulse of wavelength energy for five minutes, and it has been doing so for at least 33 years.”
“Whatever the mechanism behind this is it is unusual.”
This discovery has important implications for our understanding of the physics of neutron stars and the behavior of magnetic fields in extreme environments.
It also raises new questions about the formation and evolution of magnetism and could shed light on the origin of mysterious phenomena such as fast radio bursts.
The research team plans to make more observations of the magnetar to learn more about its properties and behaviour.
They also hope to discover more of these mysterious objects in the future, to determine if they are indeed magnets with a very long period, or even something more virtual.
The MWA is a precursor to the world’s largest radio astronomy observatory, Square Kilometer Array, which is under construction in Australia and South Africa. MWA celebrates a significant milestone this year as it completes a decade of international scientific operations and discoveries.
The International Center for Radio Astronomy Research (ICRAR) is a joint project of Curtin University and the University of Western Australia.
Provided by the International Center for Radio Astronomy Research
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