Black Holes Can Sing

While it's true that the vacuum of space cannot carry sound waves, a galaxy cluster is not entirely empty. The Perseus cluster is filled with a vast cloud of superheated gas, providing a medium through which pressure waves can travel. At its center, a supermassive black hole periodically sends out immense jets of energy, creating ripples in this gas that are, in essence, sound waves. Using NASA's Chandra X-ray Observatory, astronomers detected these faint, concentric ripples propagating outwards from the black hole, much like waves spreading from a stone dropped in a pond.

This cosmic hum was first identified in data from 2003, but it was too low for humans to ever perceive. The frequency of the note is an astonishing one million billion times deeper than the limits of human hearing. To make it audible, scientists extracted the sound waves from the X-ray data and scaled them up by 57 octaves, translating the silent ripples into an eerie, audible pitch. This process, known as data sonification, transforms non-audio data into sound, revealing the B-flat note hidden within the fabric of the galaxy cluster and giving a voice to one of the universe's most mysterious objects.