"These observations show that this explosion happened when the Universe was less than 10 per cent of its current age - the light has been travelling to us for 12 billion years,” says Professor Andrew Levan, of Radboud University, and first author of the study.

“The combination of the distance and the brightness means this explosion gave off more energy in a few seconds than the Sun will over its entire life.

“These extreme energies, along with the detection of gamma-rays by the Fermi satellite, suggest that the Fast X-ray Transients are related, at least sometimes, to the extremely powerful gamma-ray bursts that have been studied for half a century.”

“A real question is if all of the Fast X-ray Transients come from gamma-ray burst-like systems, or if there is much more diversity. Our paper shows that many of them might be gamma-ray bursts, but there are good reasons to think there is much more still to discover”