WASHINGTON - Eight billion years ago, something happened in a distant galaxy that sent an incredibly powerful blast of radio waves hurtling through the universe.
It finally arrived at Earth on June 10 last year and -- though it lasted less than a thousandth of a second -- a radio telescope in Australia managed to pick up the signal.
This flash from the cosmos was a fast radio burst (FRB), a little-understood phenomenon first discovered in 2007.
Astronomers revealed on Thursday that this particular FRB was more powerful and came from much farther away than any previously recorded, having travelled eight billion light years from when the universe was less than half its current age.
Exactly what causes FRBs has become one of astronomy's great mysteries. There was early speculation that they could be radio communication beamed from some kind of extraterrestrial, particularly because some of the signals repeat.
However scientists believe the prime suspects are distant dead stars called magnetars, which are the most magnetic objects in the universe.
Ryan Shannon, an astrophysicist at Australia's Swinburne University, told AFP it was "mind-blowing" that the ASKAP radio telescope in Western Australia had spotted the radio burst last year.
"We were lucky to be looking at that little spot in the sky for that one millisecond after the eight billion years the pulse had travelled to catch it," said Shannon, co-author of a study describing the find in the journal Science.
The FRB easily beat the previous record holder, which was from around five billion light years away, he added.
The pulse was so powerful that -- in under a millisecond -- it released as much energy as the Sun emits over 30 years.
Shannon said that there could be hundreds of thousands of FRBs flashing in the sky every day.
But around a thousand have been detected so far, and scientists have only been able to work out where just 50 came from -- which is crucial to understanding them.
Aside from trying to uncover the secrets of FRBs, scientists hope to use them as a tool to shed light on another of the universe's mysteries.