We may not be able to hear sound in space, but that doesn’t mean there isn’t sound. In 2003, astronomers detected something truly amazing: acoustic waves propagating through the gas surrounding a supermassive black hole, 250 million light-years away.
We wouldn’t be able to hear them at their current pitch. Emanating from the supermassive black hole at the center of the Perseus galaxy cluster, the waves include the lowest note in the Universe ever detected by man – well below the limits of human hearing.
However, a new sonification (data transformed into sound) not only added to the notes detected by the black hole, but raised them by 57 and 58 octaves so that we could get an idea of what they would sound like, resonating in the world. intergalactic space.
This is the first time that these sound waves have been extracted and made audible.
The lowest note, the one identified in 2003, is B-flat, just over 57 octaves below middle C; at this step, its frequency is 10 million years. The lowest note detectable by humans has a frequency of one-twentieth of a second.
Sound waves were extracted radially, or outward from the supermassive black hole at the center of the Perseus cluster, and played counter-clockwise from the center, so that we could hear the sounds in all directions from the supermassive black hole at heights 144 quadrillion and 288 quadrillion times higher than their original frequency.
The result is strange, a kind of supernatural howl (obviously), like many waves recorded from space and transposed into audio frequencies.
The sounds aren’t just a scientific curiosity, though. The tenuous gas and plasma that drift between galaxies in galaxy clusters – known as the intracluster medium – is denser and much, much hotter than the intergalactic medium outside galaxy clusters.
Sound waves propagating through the intracluster medium are one mechanism by which the intracluster medium can be heated, as they carry energy through the plasma.
Because temperatures help regulate star formation, sound waves could therefore play a vital role in the evolution of galaxy clusters over long periods of time.
This heat is also what allows us to detect sound waves. Because the intracluster medium is so hot, it shines brightly in X-rays. The Chandra X-ray Observatory enabled not only the detection of sound waves initially, but also the sonification project.
Another famous supermassive black hole also got the sonification treatment. M87*, the first black hole ever directly imaged in a colossal effort by the Event Horizon Telescope collaboration, was also imaged by other instruments at the same time. These include Chandra for X-rays, Hubble for visible light, and Atacama Large Millimeter/submillimeter Array for radio wavelengths.
These images showed a colossal jet of matter being launched from space immediately outside the supermassive black hole, at speeds that seem faster than light in a vacuum (it’s an illusion, but cool). And now they too have been sonified.
To be clear, these data weren’t sound waves to begin with, like Perseus audio, but light at different frequencies. Radio data, at the lowest frequencies, has the lowest pitch in sonification. Optical data is in the mid-range and X-ray is at the top.
Turning visual data like this into sound can be an interesting new way to discover cosmic phenomena, and the method also has scientific value.
Sometimes transforming a dataset can reveal hidden details, allowing for more detailed discoveries about the mysterious and vast universe around us.