A telescope in Canada picked up mysterious signals emanating from a distant galaxy.
There's no definitive cause of these fast radio bursts and it's unclear what caused multiple FRBs from the same location.
Theories range from highly magnetized neutron stars blasted by gas streams from a nearby supermassive black hole, to signatures of technology developed by an advanced civilisation.
Additional bursts from the repeating FRB were detected in following weeks.
"At the end of the year, we may have found 1,000 bursts", said Deborah Good, a PhD student at the University of British Columbia and one of 50 scientists from five institutions involved in the research. They don't know whether the bursts are like flashbulbs, lighting up the sky in every direction, or focused beams, which would require less energy but must be more frequent for Earth to see so many of them.
9 in the online edition of the journal Nature.
Several dozen FRBs have been recorded over the last decade, but CHIME's observations mark just the second time a repeating signal has been documented.
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"By detecting and characterizing fast radio bursts at different frequencies, we can understand better which theories work and which do not", post-doctoral fellow at McGill University, Shriharsh Tendulkar, told Cnet.
When faced with an enigma like this, the standard scientific mantra applies: we need more data. Before CHIME, astronomers noted that most of the previously detected bursts had frequencies around 1,400 MHz, and some wondered whether CHIME would detect any bursts at all in its range of 400 to 800 MHz.
The CHIME arXiv paper explained that "the output of the dedispersion transform is a 5D array of signal-to-noise ratios (SNRs), to which we apply a tunable threshold ... to identify candidate events for processing by subsequent stages of the pipeline".
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.
Using a series of four semicircular dishes, the telescope stays pointed consistently in the same direction, waiting to pick up signals.
"We have discovered a second repeater and its properties are very similar to the first repeater".
The precise nature and origin of the blasts of radio waves is unknown.
The other institutions with leading roles are the University of Toronto, the National Research Council of Canada, and the Perimeter Institute. Given that 13 FRBs were detected in such a short amount of time using pre-commissioning data, "just imagine what's waiting for us in the full-sensitivity data", she said.