The huge release of energy is thought to have emanated from a supermassive black hole some 390 million light years from Earth.
The eruption is said to have left a giant dent in the Ophiuchus galaxy cluster.
Researchers reported their findings in The Astrophysical Journal.
They had long thought there was something strange about Ophiuchus galaxy cluster, which is a giant aggregation containing thousands of individual galaxies intermingled with hot gas and dark matter. X-ray telescopes had spied a curious curved edge to it.
The speculation was that this might be the wall of a cavity that had been sculpted in its gas by emissions from a central black hole.
Black holes are famous for gorging on infalling matter, but they will also expel prodigious amounts of material and energy in the form of jets.
Scientists at first doubted their explanation however, because the cavity was so big; you could fit 15 of our own Milky Way galaxies in a row into the hole.
And that meant any black hole explosion would have to have been unimaginably prodigious.
But new telescope data from the Murchison Widefield Array (MWA) in Australia and the Giant Metrewave Radio Telescope (GMRT) in India seem to confirm it.
"In some ways, this blast is similar to how the eruption of Mount St Helens (volcano) in 1980 ripped off the top of the mountain," said Simona Giacintucci of the Naval Research Laboratory in Washington, DC, and lead author of the study.