A mysterious radio signal has been pinging in space every 1.4 hours – now we know why

For the past two decades, a strange cosmic signal has been pinging every 1.4 hours from the abyss of space.

These bursts of radio waves, called long-period radio transients, have left scientists scratching their heads since they were discovered in 2005.

Most radio waves heard in space last a few milliseconds – a second or two, tops – but these would last minutes to even an hour.

Now scientists think they finally have the answer to what’s causing these pings – ‘vampire stars’.

The vampire in question is in ASKAP J1745-5051, a star system 1.116935e+16, or 11 followed by 16 zeroes, miles away from Earth.

It’s made up of two stars – a white dwarf, the wisp left behind when a star swells and collapses on itself, and a small, dim star called a red dwarf.

This white dwarf may be no bigger than Earth, but it’s hungry. Seriously hungry. It’s devouring the red dwarf, hence the ‘vampire’ nickname.

International researchers wrote in a paper published in Nature Astronomy that too much material is adhering to the surface of the white dwarf, causing a nova explosion, which is behind the radio pings.

Lead author and PhD student Kovi Rose from the University of Sydney’s School of Physics says what makes this explosion especially interesting is that it’s also generating X-rays.

Rose said: ‘For the first time, we have pinpointed the origin of these signals, confirming the source to be a “cataclysmic variable”, or an accreting white dwarf star.’

He added: ‘Long-period radio transients have puzzled astronomers for years.

‘We’ve only found about a dozen, and their origins have been unclear. Now, we’ve been able to show that the source for one of these transients comes from a white dwarf actively pulling material from a companion star.’

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Rose said that the white dwarf is sapping material from its red counterpart, with the material heating up by millions of degrees and emitting X-rays, according to observations made by the Australian SKA Pathfinder radio telescope.

The source of the radio waves, meanwhile, is the interaction between the stars’ magnetic fields – the magnetic force released by churning sun goo.

The pair orbit one another every 1.4 hours in an oval shape, called an elliptical orbit, so they are closer together for a bit before drifting apart.

When they do nudge one another, though, their magnetic fields clash and strip each other’s surfaces. These shredded particles get spun around, releasing radio waves known to experts as synchrotron radiation.

Dr Alfredo Carpineti, an astronomer not involved in the study, told Metro that the findings don’t necessarily explain all long-period radio transients.

‘It is very exciting,’ the Invisible Rainbows author says.

‘There are many radio events in the universe that remain mysterious and connecting a signal to a source is crucial to understanding how they are produced.

‘The discovery of an X-ray signal connected but seemingly independent is even more exciting.

‘There’s a lot going on in this system and the light invisible to our senses is key to solving this mystery!’

Rose called his team’s finding the ‘stellar Rossetta stone’ for future discoveries, referring to the Egyptian granite slab covered in classical Greek, hieroglyphs and an Egyptian shorthand called Demotic.

As the stone helped translate languages, the findings, Rose said, could help differentiate types of long-period radio transients.

His team now hope to continue studying the system using radio, optical, and X-ray telescopes to better understand the signals.

‘Each new discovery is helping us piece together the bigger picture,’ Rose said. ‘We’re only just beginning to understand this new class of cosmic events.’

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