Astronomers trace 'Treble Clef' radio structure to black hole eruption and galaxy cluster merger

Key facts

• Astronomers traced the origin of a radio-wave formation nicknamed the 'Treble Clef' to an ancient supermassive black hole outburst followed by a collision between two galaxy clusters.
• The research, led by Andrea Botteon of Italy's National Institute for Astrophysics (INAF), combined data from NASA's Chandra X-ray Observatory, ESA's eROSITA telescope, the LOFAR radio telescope network and the United Kingdom Infrared Telescope (UKIRT).
• The formation lies behind the plane of the Milky Way, making it hard to observe because foreground stars, gas and dust obscure the region.
• The black hole eruption produced bright radio emissions from particles moving at near light speed; the emission faded as particles lost energy, but the later cluster collision compressed the cloud or re-energised its particles, reviving the radio glow, possibly aided by shock waves.
• X-ray observations from Chandra showed the hot gas is oval-shaped with stronger emission on either side of the cluster centre, indicating the collision occurred roughly left to right in the image.
• Scientists estimate the direct collision between the two clusters occurred a few hundred million years ago, and the clusters are now moving apart.
• The study was published in Astronomy & Astrophysics, and the 'Treble Clef' resemblance is an example of pareidolia with no physical connection to music.