Mysterious radio signal picked up from space has astronomers baffled


Stranges pulses from the depths of space led astronomers to find a new kind of neutron star (Credits: PA)

Astronomers have followed a mysterious radio signal from outer space to the discovery of a neutron star unlike any previously found.

The story begins with Manisha Caleb, a lecturer at the University of Sydney.

She and her colleagues were observing the Vela-X 1 region of the Milky Way – a part of space that’s around 1,300 light years away from Earth.

They were using the MeerKAT radio telescope in South Africa when they noticed a strange-looking flash or ‘pulse’ that lasted about 300 milliseconds.

‘The flash had some characteristics of a radio-emitting neutron star. But this wasn’t like anything we’d seen before,’ she said.

A neutron star is the collapsed remains of a massive supergiant star. Apart from a black hole, they are the smallest and densest stellar objects known to man.

When they’re especially dense, they can be called pulsars – and often emit bursts of radio waves that we can pick up here on Earth.

Radio Telescope Observatory under starry night

The team used the MeerKAT radio telescope in South Africa to discover the bursts (Credits: Getty Images)

‘Our observation showed PSR J0941-4046 [which is what they named the star] had some of the characteristics of a “pulsar” or even a “magnetar”. Pulsars are the extremely dense remnants of collapsed giant stars which usually emit radio waves from their poles,’ explained Caleb.

‘As they rotate, the radio pulses can be measured from Earth, a bit like how you’d see a lighthouse periodically flash at the distance.

‘However, the longest known rotation period for a pulsar before this was 23.5 seconds – which means we might have found a completely new class of radio-emitting object. Our findings are published in Nature Astronomy.’

Inside a star graveyard

As well as finding a neutron star sending out pulses unlike anything we’ve seen before, the team also discovered it lies within a neutron star “graveyard.”

This particular region of space that PSR J0941-4046 exists in is believed to be filled with neutron stars at the end of their life cycle.

EMBARGOED TO 1600 WEDNESDAY JANUARY 26 Undated handout artist's impression issued by ICRAR of what the object might look like if it's a magnetar.  A mysterious object unlike anything ever seen before has been spotted by astronomers.  The researchers think it could be a neutron star or a white dwarf - collapsed cores of stars - with an ultra-powerful magnetic field.  Issue date: Wednesday January 26, 2022. PA Photo.  See PA story SCIENCE Object.  Photo credit should read: ICRAR/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption.  Reuse of the picture may require further permission from the copyright holder.

An artist’s impression of what a neutron star could look like if it’s a magnetar (Credits: PA)

Some of them aren’t as active, while others may be completely dead and inert.

‘PSR J0941-4046 challenges our understanding of how neutron stars are born and evolve,’ Caleb said.

‘It’s also fascinating as it appears to produce at least seven distinctly different pulse shapes, whereas most neutron stars don’t exhibit such variety. This diversity in pulse shape, and also pulse intensity, is likely related to the unknown physical emission mechanism of the object.’

We’ll leave you to wonder about what she means by ‘unknown physical emission mechanism’.

Calbe continued: ‘One particular type of pulse shows a strongly “quasi-periodic” structure, which suggests some kind of oscillation is driving the radio emission. These pulses may provide us with valuable information about the inner workings of PSR J0941-4046.

‘These quasi-periodic pulses bear some resemblance to enigmatic fast radio bursts, which are short radio bursts of unknown origin.

‘However, it’s not yet clear whether PSR J0941-4046 emits the kind of energies observed in fast radio bursts.’

This animation depicts a neutron star (RX J08064-4123) with a disk of warm dust that produces an infrared signature as detected by NASA???s Hubble Space Telescope.  The disk wasn???t directly photographed, but one way to explain the data is by hypothesizing a disk structure that could be 18 billion miles across.  The disk would be made up of material falling back onto the neutron star after the supernova explosion that created the stellar remnant.  Credits: NASA, ESA, and N. Tr???Ehnl (Pennsylvania State University)

This image depicts a neutron star with a disk of warm dust that produces an infrared signature around it (Credits: Space Telescope Science Institute)

Of course, as with any deep space discovery, the scientists simply replace answers with more questions.

How long has this neutron star been active? Are there other stars like this one out in the galaxy? Is it even a neutron star in the classic sense or do we need to invent a new kind of object to classify it?

‘Detecting sources is challenging, which implies there may be a larger undetected population waiting to be discovered,’ Caleb said.

She concluded: ‘Our finding also adds to the possibility of a new class of radio transient: the ultra-long period neutron star. Future searches for similar objects will be vital to our understanding of the neutron star population.’

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