The “Treble Clef”—a radio wave formation spanning space in the distinct shape of a musical symbol—is the byproduct of an outburst from a supermassive black hole, followed by a collision between two galaxy clusters.
New data from NASA’s Chandra X-ray Observatory has clarified the origin of this cosmic structure, revealing it to be the result of a supermassive black hole’s activity, later re-energized by the merger of two galaxy clusters.
A paper describing the findings, led by Andrea Botteon of the National Institute for Astrophysics (INAF) in Italy, was published Wednesday in the Astronomy & Astrophysics journal.
Researchers identified the object within a galaxy cluster by using Chandra and the German Extended RÖntgen Survey with an Imaging Telescope Array (eROSITA) to detect diffuse, hot gas. Galaxy clusters, which contain hundreds of individual galaxies and vast reservoirs of superheated gas, are some of the largest structures in the universe. The study confirms that this specific cluster is currently in the process of merging.
A composite image of the Treble Clef highlights the multimillion-degree gas in blue, captured by Chandra and eROSITA, while the radio data appears in red. The latter was provided by the LOw Frequency ARray (LOFAR), a large network of radio telescopes in Europe. To emphasize these features, the authors utilized a special technique on the Chandra data.
The formation’s shape—a vertical stroke with a continuous, fluid line—is the result of a two-stage evolution. Initially, a supermassive black hole ejected charged particles and magnetic fields, creating bright radio waves. These waves eventually faded and lost energy, only to be compressed and re-energized when the two galaxy clusters collided.
The researchers think the direct collision between the two clusters occurred a few hundred million years ago, and the clusters are now moving away from each other.
While the resemblance to a musical notation is striking, scientists classify it as a case of pareidolia, the phenomenon when people see familiar shapes in random data. Beyond the visual coincidence, there is no scientific connection to the musical symbol.