We may not be able to hear a sound in space, but that does not mean that there is no sound. In 2003, astronomers discovered something truly amazing: sound waves propagate through the gas surrounding a supermassive black hole, 250 million light-years away.
We won’t be able to hear them in the current stadium. Emerging from the supermassive black hole at the center of the Perseus cluster of galaxies, the waves include the lowest pitch in the universe ever detected by humans — well below the limits of human hearing.
However, the new sonication (data turned into sound) not only added to the observations detected from the black hole, but brought it 57 and 58 octaves so we could get a sense of what it might sound like, resonating through intergalactic space.
It is the first time that these sound waves have been extracted and made audible.
The lowest pitch, identified in 2003, is B-flat, just over 57 octaves below middle C; In this ballpark, its frequency is 10 million years. The lowest tone that can be detected 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 in a counterclockwise direction from the center, so that we could hear sounds in all directions from the supermassive black hole at tones 144 quadrillion and 288 quadrillion times higher than its original frequency.
The result is a frightening, sort of extraterrestrial howl (pronounced), like many waves recorded from space and converted into sound frequencies.
However, the sounds aren’t just a scientific curiosity. The weak gas and plasma that drifts between galaxies in galaxy clusters – known as the medium within a cluster – is much denser and hotter than the intergalactic medium outside of galaxy clusters.
One of the mechanisms by which the inner cluster medium can be heated is that sound waves propagate through the inner cluster medium, transmitting energy through the plasma.
Since temperatures help regulate star formation, sound waves may play a vital role in the evolution of galaxy clusters over long periods of time.
This temperature is what allows us to detect sound waves as well. Because the medium inside the cluster is extremely hot, it glows brightly in X-rays. The Chandra X-ray Observatory allows not only to detect sound waves at first, but to project the sonication.
A famous supermassive black hole has also received the sonication treatment. M87*, the first black hole directly imaged in a massive effort by the Event Horizon Telescope, was also imaged by other instruments at the same time. These include the Chandra for X-rays, the Hubble for visible light, and the Atacama Large Millimeter/submillimeter Array for radio wavelengths.
Those images showed a massive jet of material shooting out from space directly out of a supermassive black hole, at speeds that appear faster than light in a vacuum (it’s an illusion, but it’s cold). And now, they too have been reconciled.
To be clear, these data weren’t sound waves to begin with, like Perseus’s voice, but rather light at different frequencies. Radio data, at the lowest frequencies, has the lowest sonication. Optical data bears the mid-range, and X-rays are at the top.
Converting visual data like this to sound could be a great new way to experience cosmic phenomena, and the method has scientific value as well.
Sometimes transforming a data set can reveal hidden details, allowing for more detailed discoveries about the vast, mysterious universe around us.