Canadian scientists have discovered a series of radio signals, one of which is repetitive, being emitted from an unknown location billions of light-years away.
The findings were published in Nature science journal on Wednesday.
In total, 13 individual bursts were detected by Canada's radio telescope, the Canadian Hydrogen Intensity Mapping Experiment (CHIME), over a period of three weeks in 2018.
Repeated bursts from one "fast radio burst" FRB were observed in the weeks following.
This repetitive FRB is the second of its kind to ever be discovered — the first was found in 2015.
What do we know about the fast radio burst (FRB)?
FRBs are bursts of radio waves from an unknown origin in deep space, but CHIME's team believe the source is a "powerful astrophysical object more likely to be in a location with special characteristics."
"That could mean in some sort of dense clump of supernova remnant," Cherry Ng, a member of the CHIME team and an astronomer at the University of Toronto, said. "Or near the central black hole in a galaxy."
Euronews spoke with Shriharsh Tendulkar, the study author and astronomer at McGill University, who said the phenomena could be linked to neutron stars, which are very compact and dense.
Specifically, the individual FRBs could be caused by the merging of two neutron stars, however, this is only one explanation possible for the singular FRB signals.
The repetitive FRB could be explained by activity on the neutron star, sort of "an earthquake or a jolt that emits a burst. It's like a snapping of a magnetic field," Tendulkar said.
But, apart from this, the extragalactic signals are quite the mystery.
"Until now, there was only one known repeating FRB," Ingrid Stairs, another member of the CHIME team and astrophysicist at University of British Columbia (UBC) said. "Knowing that there is another suggests that there could be more out there."
"And with more repeaters and more sources available for study, we may be able to understand these cosmic puzzles — where they're from and what causes them."
When asked about the next stage of CHIME's project, Tendulkar said the group was working with its colleagues around the globe to detect and understand more about the repetitive burst.
"We will try to localise it, and work out which galaxy it is from," he said.
Could this be a sign of extraterrestrial activity?
While the idea that FRBs are a sign of alien activity hasn't been entirely ruled out, the majority of experts think chances are pretty slim.
Tendulkar told Euronews it was "extremely unlikely" that the FRBs were caused by extraterrestrial beings, and that his team would look to rule out all other physical theories before considering this possibility.
NASA research scientist Dr Jessie Christiansen echoed Tendulkar's sentiment, saying "astronomers are super excited to find out more, but generally do not think it is extraterrestrial."
While Tendulkar and Christiansen quashed speculation gently, other experts saw the funny side.
"It 'could be' a signal sent back in time by humans to warn us that we write too many 'could be aliens' stories, and everyone in the future is kind of embarrassed for us," physicist Robert McNees joked, poking fun at some of the world's media that immediately jumped to questions about theories of aliens using FRBs to contact Earth.
"There are so many possibilities, really," he added.
However, some people chose to keep an open mind to the possibilities.
"At this point, we simply don't know what is causing [FRBs]," space writer Paul Scott Anderson said. "Are they natural? Probably, given the history."
"But we should also avoid a knee-jerk reaction to such discoveries — it 'can't be aliens, therefore it isn't.'"
"One of these times, maybe it will be."