The blast, which released five times more energy than the previous record holder, came from a
The other telescopes used for the discovery included NASA's Chandra X-ray Observatory, European Space Agency's (ESA) XMM-Newton and the Murchison Widefield Array (MWA) in Western Australia.
"We've seen outbursts in the centres of galaxies before but this one is really, really massive," said Professor Melanie Johnston-Hollitt from the Curtin University node of the International Centre for Radio Astronomy Research in Australia.
"And we don't know why it's so big. But it happened very slowly - like an explosion in slow motion that took place over hundreds of millions of years," she added.
The explosion occurred in the Ophiuchus galaxy cluster, about 390 million light-years from Earth. It was so powerful it punched a cavity in the cluster plasma -- the super-hot gas surrounding the black hole.
The blast was similar to the 1980 eruption of Mount St. Helens, which ripped the top off the mountain, said lead author of the study Simona Giacintucci from the Naval Research Laboratory in the US.
"The difference is that you could fit 15 Milky Way galaxies in a row into the crater this eruption punched into the cluster's hot gas," she said.
The cavity in the cluster plasma had been seen previously with X-ray telescopes, Johnston-Hollitt said.
But scientists initially dismissed the idea that it could have been caused by an energetic outburst, because it would have been too big.
"People were sceptical because the size of outburst," she said. "But it really is that. The Universe is a weird place."
The researchers only realised what they had discovered when they looked at the Ophiuchus galaxy cluster with radio telescopes.
"The radio data fit inside the X-rays like a hand in a glove," said co-author Maxim Markevitch, from NASA's Goddard Space Flight Centre.
"This is the clincher that tells us an eruption of unprecedented size occurred here," Markevitch said.
Professor Johnston-Hollitt likened the finding to discovering the first dinosaur bones.
"It's a bit like archaeology," she said.
"We've been given the tools to dig deeper with low frequency radio telescopes so we should be able to find more outbursts like this now," Johnston-Hollitt said.
See also:
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An explosion 4 billion lightyears from Earth released more energy than the Sun can generate in its entire lifespan