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 the physics of neutron stars.
The object could be an ultra-long-period magnetar, a rare type of star with very strong magnetic fields that can generate powerful bursts of energy.
Until recently, all known magnets emitted energy at intervals ranging from a few seconds to a few minutes. The newly discovered object emits radio waves every 22 minutes, making it the longest magnet ever discovered.
The research was published in the journal Nature.
The object was discovered by astronomers using the Murchison Widefield Array (MWA) radio telescope in Western Australia’s Wajari Yamaji Kingdom.
Lead author Dr Natasha Hurley-Walker said the magnetar, named GPM J1839−10, is 15,000 light-years from Earth in the constellation Scutum.
“This remarkable object challenges our understanding of neutron stars and magnetars, which are some of the strangest and most extreme objects in the universe,” she said.
The stellar object is the second to be discovered so far, following the first one by Tyrone O’Doherty, a graduate research student at Curtin University.
At first, scientists could not explain what they found.
They published a paper Nature In January 2022, it describes a mysterious transient object that appears and disappears intermittently, emitting powerful beams of energy three times an hour.
Dr Hurley-Walker, O’Doherty’s Honors Supervisor, said: “We were surprised by the first object.
“We were stunned,” she said. “So we started looking for similar objects to see if this was an isolated incident or just the tip of the iceberg.”
Between July and September 2022, the team scanned the sky with the MWA telescope.
They soon 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 characteristics.
These include the three 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 characteristics of GPM J1839−10, the team also began searching the observational archives of the world’s leading radio telescopes.
“This was shown in observations by the Giant Metrowave Radio Telescope (GMRT) in India, and the Very Large Array (VLA) in the US made observations until 1988,” she said.
“It was an incredible moment for me. I was five years old when our telescope first recorded pulses from this object, but no one noticed, and it remained hidden in the data for 33 years.
“They missed it because they didn’t expect to find something like that.”
Not all magnets generate 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 emission.
“The object we found is rotating too slowly to produce radio waves—it’s below the death line,” Dr Hurley-Walker said.
“Supposing it is a magnet, this object cannot generate radio waves. But we see them.
“We’re not talking about a small spike in radio emissions.
“Every 22 minutes, it emits a five-minute pulse of radio-wavelength energy, and has done so for at least 33 years.
“Any mechanism behind this is extraordinary.”
The discovery has important implications for our understanding of the physics of neutron stars and the nature of magnetic fields in extreme environments.
This will raise new questions about the formation and evolution of magnetars and shed light on the origin of mysterious phenomena such as fast radio bursts.
The research team plans to conduct further observations of the magnetar to learn more about its properties and characteristics.
They also hope to find more of these mysterious objects in the future to determine if they are actually ultra-long-period magnets or something more unusual.
MWA is the precursor to the world’s largest radio astronomy observatory, the Square Kilometer Array, under construction in Australia and South Africa. MWA celebrates a significant milestone this year, completing a decade of activities and international scientific discovery.
The International Center for Radio Astronomy Research (ICRAR) is a joint venture between Curtin University and the University of Western Australia, supported and funded by the State Government of Western Australia.