Mysterious repeating energy bursts from deep space that some experts have suggested could be evidence of advanced aliens have been detected for the second time.
The repeating bursts are an example of what are known as fast radio bursts (FRBs), millisecond-long flashes of radio waves whose origin is unknown.
Most scientists believe they are generated by powerful astrophysical phenomena such as black holes or super-dense neutron stars. But a few scientists have suggested more outlandish theories.
Prof Avid Loeb, from the Harvard-Smithsonian Centre for Astrophysics in the US, argues that they could be evidence of incredibly advanced alien technology.
FRBs were first detected accidentally in 2007, when a burst signal was spotted in radio astronomy data collected in 2001.
The new discovery, reported in the journal Nature, was made by a Canadian-led team of astronomers on the hunt for FRBs.
Over a period of three weeks last summer, the team detected 13 FRBs using a new type of radio telescope, the Canadian Hydrogen Intensity Mapping Experiment (Chime).
Where the FRBs come from is not known, although they are thought to emanate from sources billions of light years away outside our galaxy, the Milky Way.
Chime astrophysicist Dr Ingrid Stairs, from the University of British Columbia, Canada, said: “Until now, there was only one known repeating FRB.
“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.”