Mysterious radio signal picked up from space has baffled astronomers

Mysterious radio signal picked up from space has baffled astronomers

Milky Way

Strange pulses from the depths of space have led astronomers to find a new type of neutron star (Credits: PA)

Astronomers have tracked a mysterious radio signal from outer space to the discovery of an unprecedented neutron star.

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

She and her colleagues were observing the Vela-X 1 region of the Milky Way, a portion of space about 1,300 light-years from Earth.

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

“The flash had some characteristics of a neutron star emitting radio frequencies. But it was unlike anything we had seen before,” she said.

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

When particularly 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 (Credit: 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 that typically radiate radio waves from their poles,” Caleb explained.

“As they spin, radio pulses can be measured from Earth, much like seeing a lighthouse periodically flashing in the distance.

“However, the longest known rotation period for a pulsar before that was 23.5 seconds – meaning we could have found a whole new class of radio-emitting objects. Our findings are published in Nature Astronomy.

Inside a graveyard of stars

As well as finding a pulsating neutron star unlike anything we’ve seen before, the team also discovered that it’s in a neutron star “graveyard.”

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

EMBARGOED TO 1600 WEDNESDAY JANUARY 26 Undated artist's impression issued by ICRAR of what the object might look like if it were a magnetar.  A mysterious object unlike any 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-strong 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 photo may only be used for editorial reporting purposes for the contemporaneous illustration of events, things or people in the picture or facts mentioned in the caption.  Reuse of the image may require additional permission from the copyright holder.

Artist’s impression of what a neutron star might look like if it were a magnetar (Credits: PA)

Some of them are not as active, while others may be completely dead and inert.

“PSR J0941-4046 challenges our understanding of the birth and evolution of neutron stars,” Caleb said.

“It is also fascinating because it appears to produce at least seven distinct pulse shapes, whereas most neutron stars do not show such variety. This diversity in pulse shape, as well as pulse intensity, is likely related to the object’s unknown physical emission mechanism.

We’ll leave you wondering what she means by “unknown physical emission mechanism.”

Calbe continued, “One particular type of pulse shows a strongly ‘quasi-periodic’ structure, suggesting that some sort of oscillation is causing the radio emission. These pulses can provide us with valuable information about the inner workings of the PSR J0941-4046.

“These quasi-periodic pulses look somewhat like enigmatic fast radio bursts, which are short radio bursts of unknown origin.

“However, it is not yet clear whether PSR J0941-4046 emits the type of energy seen in fast radio bursts.”

This animation depicts a neutron star (RX J0806.4-4123) with a disk of hot dust that produces an infrared signature detected by NASA's Hubble Space Telescope.  The disk has not been directly photographed, but one way to explain the data is to hypothesize a disk structure that could be 18 billion kilometers in diameter.  The disk would be composed 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 shows a neutron star with a disk of hot dust that produces an infrared signature around it (Credits: Space Telescope Science Institute)

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

How long has this neutron star been active? Are there other stars like this in the galaxy? Is it even a neutron star in the classical sense of the term or must we invent a new type of object to classify it?

“Detecting similar sources is a challenge, which implies that there may be a larger undetected population waiting to be discovered,” Caleb said.

She concluded: “Our discovery also adds to the possibility of a new class of radio transients: the ultra-long-period neutron star. Future searches for similar objects will be critical to our understanding of the neutron star population.

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