A radio source shaped like a treble clef appears to be the remnant of a black-hole outburst revived by a galaxy-cluster collision. A new Chandra release on October 14 brings together observations that help explain the unusual structure.
The object sits about 1.55 billion light-years away, almost behind the plane of the Milky Way. Stars, gas and dust in our own galaxy obscure the view. X-rays and radio observations let researchers examine what ordinary visible-light images hide.
Chandra and eROSITA detected a broad cloud of hot gas, showing that the radio structure belongs to a galaxy cluster. The researchers identify two clusters in the process of merging.
Their interpretation involves two stages. An earlier outburst from a supermassive black hole sent charged particles and magnetic fields outward. The radio emission faded as those particles lost energy. The later collision compressed or reenergized the material, making it bright again.
The paper classifies the object as a radio phoenix, an old radio source whose emission has been revived. The detailed role of gas motions remains an interpretation of the observations, rather than a directly witnessed sequence of events.
To examine the collision, the team removed a smooth, symmetrical component from the X-ray data. Remaining emission highlighted differences across the cluster.
The musical resemblance is simply a familiar shape seen in an astronomical structure. The observations concern hot gas, charged particles and magnetic fields. No sound was recorded.
