According to Space.com, the explosion was observed in a region of deep space 390 million light-years from us known as the Ophiuchus cluster. Because of — you know – relativity, the event must have occurred 390 million actual years ago, with the light from the explosion only reaching our best telescopes now. Given the sheer enormity of the event, Giacintucci and her team at the Naval Research Lab pegged the culprit as a supermassive black hole. They hypothesized that jets of radiation from a black hole at the center of one of the Ophiuchus galaxies may be the source of the calamity.

The observations that led to this discovery actually date back to a 2016 study by Norbert Werner who examined data from NASA’s Chandra X-ray Observatory. Some of those images apparently showed anomalous curved structures at the edges of the cluster, which Werner and his team believed to be the outlines of a massive “crater” left behind by the explosion. For the last four years, Werner’s theory was unproven, but the data collected by Giacintucci and her team seems to confirm his thinking.

The new findings appear in the Feb. 27th issue of The Astrophysical Journal.