Astronomers have detected baffling, previously unseen behaviour from a rare ‘magnetar’ star - one of the most powerful magnets in the universe.
Magnetars are formed when stars collapse, and some scientists believe they could be a source for ‘fast radio bursts’ – mysterious radio signals received on Earth.
The new study could help scientists understand how and why magnetars form – and if they are the source of strange radio bursts picked up by telescopes on our planet.
Only about 30 magnetars have been detected in and around our own Milky Way galaxy – but even among those, the new magnetar is unusual.
Like a handful of other magnetars, it emits radio pulses similar to pulsars, the less magnetic cousins of magnetars that produce beams of radio waves from their magnetic poles.
But the pulses emitted by J1818 were bright at low frequencies, and much more like pulsars.
Scientists observed it eight times using the CSIRO Parkes radio telescope between May and October 2020.
This ‘identity crisis’ behaviour reached a peak in July where they saw it flicking back and forth between emitting pulsar-like and magnetar-like radio pulses.
The paper is on the pre-print server ArXiv.
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Lead author Marcus Lower, of Swinburne University/CSIRO, said: “This bizarre behaviour has never been seen before in any other radio-loud magnetar.
“It appears to have only been a short-lived phenomenon as by our next observation it had settled permanently into this new magnetar-like state.”
"I think it is safe to call it a potential missing link,” Lower said in an interview with ScienceAlert.
"At this stage there's still a lot we don't know about this new magnetar, but there are clear similarities between it and the high-magnetic field pulsars.”
Analysis of the signals from the star found that its magnetic poles are highly unusual, too.
The researchers believe that the radio pulses from J1818 originate from loops of magnetic field lines connecting two closely spaced poles, like those seen connecting the two poles of a horseshoe magnet or sunspots on the sun.
“From our observations, we found that the magnetic axis of J1818 isn’t aligned with its rotation axis,” says Lower.
“Instead, the radio-emitting magnetic pole appears to be in its southern hemisphere, located just below the equator.
“Most other magnetars have magnetic fields that are aligned with their spin axes or are a little ambiguous.”
“This is the first time we have definitively seen a magnetar with a misaligned magnetic pole.”
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