A cosmic treble clef, traced to a black hole's outburst and a collision of galaxy clusters

Astronomers have been puzzling over a glowing formation shaped, delightfully, like a treble clef, hiding behind the plane of our own Milky Way. A team led by Andrea Botteon at Italy's INAF observatory has now pieced together its story using NASA's Chandra telescope plus eROSITA, the LOFAR radio array and infrared data: first, a supermassive black hole erupted and lit the cloud up; then, a few hundred million years ago, two galaxy clusters crashed into each other sideways, re-energising the whole structure. The work, published in Astronomy & Astrophysics, turns a musical curiosity into a fossil record of two of the most violent events a universe can stage.