Signals from a Black Hole

In space, there is no sound. Actually, no. Voyager 1 is renowned for capturing the sounds of all the large planets in the solar system. However, plasma vibrations, radio waves, electromagnetic disruptions, and charged particles interacting with the many things in the depths of space can be converted into sound waves for our ears.

300 million light-years away in the Perseus galaxy cluster, emissions from a probable supermassive black hole have been singing the same note for 2.5 billion years, registering (once translated) 57 octaves below middle C. Scientists believe that the recordings are the result of materials exiting the black hole's accretion disk even if the signal's exact cause is yet unknown.

However, people do observe intense emissions coming from the poles of supermassive black holes, known as relativistic jets, which can shoot gas and supercharged particles across millions and millions of light-years of distance. You might object, "But I thought that nothing could escape a black hole's gravity well!" and you would be mostly correct.