Scientists were left bamboozled after hearing apparent bird sounds in space.
A recently published study looked at chorus waves. They're described as 'the strongest electromagnetic emissions naturally occurring in space and can cause radiation that is hazardous to humans and satellites'.
These 'waves' travel along Earth’s magnetic field lines and transfer energy to electrons, accelerating them to energies close to the speed of light; sometimes creating auras like the Northern Lights.
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While they may make beautiful auras, chorus waves are also dubbed 'killer electrons' because of the threat they pose to satellites, astronauts, and vital communication systems.
Chorus waves themselves are nothing new to science boffins across the globe, but they were recently discovered in an unexpected place - that being over 100,000km (62,000 miles) from Earth.
Typically they're found around 51,000km (32,000 miles) from our planet and were first discovered by World War I radio operators who heard the bird-like sounds while listening for enemy signals.
The unusual plasma waves have been studied ever since.
The new discovery was made by scientists at Beihang University in China, who analyzed data from NASA's Magnetospheric Multiscale (MMS) satellites.
When converted to audio signal, chorus waves translate to bird-like chirping sounds and, while researchers have heard this distinct noise before, they've never heard it from so far away.
Speaking about the discovery, Allison Jaynes, a space physicist at the University of Iowa who was not involved with the work, said: "That opens up a lot of new questions about the physics that could be possible in this area."
"It’s very captivating, very compelling," she went on. "We definitely need to find more of these events."
Elsewhere, Richard Horne, a space weather expert with the British Antarctic Survey, said in an online commentary that the findings were 'a surprising result in a surprising region'.
As to why the discovery of the chorus waves over 100,000km away is so big, it implies the waves don’t need Earth’s environmental conditions to form, says BBC's Science Focus, as previously thought.
Horne thinks that the discovery 'doesn't rule out the existing theory' though. This is because 'the expected magnetic field gradients could still be present, but it means that scientists need to take a closer look', he says.
With the ongoing debates about what truly causes chorus waves, researchers now hope that their newly published findings will 'help to resolve long-standing controversies regarding chorus emissions and in gaining an understanding of the energy transport observed in space and astrophysical environments'.
Niamh Shackleton