I was flicking through the TV channels last week when I stumbled upon BBC 4’s Hubble Telescope documentary. My boyfriend uses Hubble’s pictures for his research so we decided to watch. I’m more interested in X-ray astronomy, so was delighted when they mentioned a charming discovery by NASA’s X-ray Observatory Chandra in 2003.

Scientists from Cambridge, England, looked at X-ray images of Perseus, the brightest cluster of galaxies in the night sky. They found the supermassive blackhole at the centre of the cluster emitted sound waves. The pitch of the waves is B flat, but it is 429 notes below the lowest key on a piano; a frequency over a million billion times deeper than the limits of human hearing.

The sound waves are created by the high energy halo around the black hole, which compresses and rarefies the hot gas around it. This makes the gas hum the note of B flat. Earlier studies had detected light and heat emitted by black holes, so scientists were not surprised to find sound waves too.

You can visit the NASA photo album of the Perseus cluster here: http://chandra.harvard.edu/photo/2003/perseus/more.html