NASA shares a clip of how a black hole sounds and it's eerie

This week, NASA shared what a supermassive black hole would sound like. This black hole, at the center of the Perseus cluster of galaxies, is 250 million light years away from Earth. It sounds extremely terrifying—like an unearthly howling.

NASA wrote that this sonification is unlike any other done before because it "revisits the actual sound waves discovered in data from NASA's Chandra X-ray Observatory." NASA also clarified a "popular misconception" that leads people to believe that because most of space is essentially a vacuum, providing no medium for sound waves to propagate through, there is no sound in space. It said, "A galaxy cluster has so much gas that we've picked up actual sound. Here it's amplified, and mixed with other data, to hear a black hole!" NASA Exoplanets, a team at the agency focused on planets and other information outside of our solar system, also tweeted the 34-second clip. 

NASA published this brand-new sonification, or the conversion of astronomical data into sound, as part of Black Hole Week. The Perseus black hole has previously been associated with sound since 2003. It is because "the pressure waves sent out by the black hole caused ripples in the cluster’s hot gas that could be translated into a note." The waves contained the lowest note ever heard by humans and are well below the threshold of human hearing. For the acoustic waves emanating from this black hole at the center of the Perseus cluster of galaxies to be audible to human ears, they had to be transposed up 57 and 58 octaves, according to a post on NASA's website.  

The website also mentions that "the sound waves astronomers previously identified were extracted and made audible for the first time." We can now hear what the black hole's notes would sound like if they were ringing through intergalactic space. The website reads, "Another way to put this is that they are being heard 144 quadrillion and 288 quadrillion times higher than their original frequency. (A quadrillion is 1,000,000,000,000,000.) The radar-like scan around the image allows you to hear waves emitted in different directions. In the visual image of these data, blue and purple both show X-ray data captured by Chandra."

Another well-known supermassive black hole was sonified as well. In a massive effort by the Event Horizon Telescope (EHT) collaboration, M87, the first black hole to ever be directly imaged is now sonified across the three-tiered image from left to right, with each wavelength mapped to a different range of audible tones. Studied by scientists for decades, Messier 87, or M87 black hole, gained a lot of popularity when it became the first black hole to be imaged by the EHT, along with other instruments in 2019. "Radio waves are mapped to the lowest tones, optical data to medium tones, and X-rays detected by Chandra to the highest tones," according to NASA. These include the Atacama Large Millimeter/ submillimeter Array for radio wavelengths, Hubble for visible light, and Chandra for X-rays. However, unlike the audio from Perseus, this data did not originate as sound waves, but rather as different frequencies of light. "The brightest part of the image corresponds to the loudest portion of the sonification, which is where astronomers find the 6.5-billion solar mass black hole that EHT imaged," explained NASA.

Black-hole enthusiasts can listen to many more such interesting sonifications of cosmic objects on the A Universe of Sound website.