Chandra’s 53-hour observation of the central region of the Perseus galaxy cluster (left) has revealed wavelike features (right) that appear to be sound waves. The features were discovered by using a special image-processing technique to bring out subtle changes in brightness. These sound waves are thought to have been generated by explosive events occurring around a supermassive black hole (bright white spot) in Perseus A, the huge galaxy at the center of the cluster. The image also shows two vast, bubble-shaped cavities filled with high-energy particles and magnetic fields. They create the sound waves by pushing the hot X-ray emitting gas aside. The pitch of the sound waves translates into the note of B flat, 57 octaves below middle-C. This frequency is over a million billion times deeper than the limits of human hearing, so the sound is much too deep to be heard.