We may not be able to hear sound in space, but that doesn’t mean there isn’t any. In 2003, astronomers detected something truly amazing: acoustic waves propagating through gas surrounding a supermassive black hole, 250 million light-years away.
We couldn’t hear them in their current tone. 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 humans, well below the limits of human hearing.
However, a new sonification (data converted to sound) not only added to the notes detected from the black hole, but also raised them by 57 and 58 octaves so we can get an idea of what they would sound like, resonating through space. intergalactic.
It is the first time that these sound waves have been extracted and made audible.
The lowest note, the one identified in 2003, is a flat B, a little more than 57 octaves below middle C; at that pitch, its frequency is 10 million years. The lowest note detectable by humans has a frequency of one-twentieth of a second.
The sound waves were drawn radially, or outward, from the supermassive black hole at the center of the Perseus cluster, and played counterclockwise from the center, so that we can hear the sounds in all directions from the supermassive black hole at pitches 144. quadrillion and 288 quadrillion times greater than its original frequency.
The result is haunting, a kind of unearthly howl (obviously), like many of the ripples recorded from space and transposed to audio frequencies.
However, the sounds are not just a scientific curiosity. The tenuous gas and plasma that travels 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 play a vital role in the evolution of galaxy clusters over long periods of time.
That heat is what allows us to detect sound waves as well. 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 to be 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 the Atacama Large Millimeter/submillimeter Array for radio wavelengths.
Those images showed a colossal jet of material launched from space immediately outside the supermassive black hole, at speeds that seem faster than the speed of light in a vacuum (it’s an illusion, but cool). And now, they too have been sonified.
To be clear, this data wasn’t sound waves to begin with, like the Perseus audio, but rather light at different frequencies. Radio data, at the lowest frequencies, has the lowest pitch in sonification. Optical data occupies the middle range and X-rays are at the top.
Converting visual data like this to sound may be a cool new way to experience cosmic phenomena, and the method has scientific value as well.
Sometimes transforming a dataset can reveal hidden details, allowing for more detailed discoveries about the vast and mysterious Universe around us.