The black hole at the centre of the Perseus cluster emits pressure waves that can be translated into sound.
Why it is true
The black hole at the centre of the Perseus cluster generates pressure waves in the hot gas surrounding it. These acoustic waves, transposed up 57 octaves, become audible as a very low sound, similar to a deep hum.
Source: NASA
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.
Related facts
If you fell into a black hole, you would experience 'spaghettification'.
A black hole can 'burp' after devouring a star.
The Milky Way has a supermassive black hole at its centre, called Sagittarius A.
A supermassive black hole was expelled from its galaxy and is creating stars along its path.
