You can’t hear the black hole screaming in space, but it sounds like you can hear it sing.
In 2003, astrophysicists working with NASA’s Chandra X-ray Observatory detected a pattern of ripples in the X-ray glow of a giant group of galaxies in the constellation Perseus. They were pressure waves – that is, sound waves – spanning 30,000 light-years and radiating outward through the thin, superheated gas that fills the galaxy clusters. They were caused by periodic explosions from a supermassive black hole at the center of the cluster, which is 250 million light-years away and contains thousands of galaxies.
With an oscillation period of 10 million years, the sound waves were acoustically equivalent to a B-flat 57 octaves below middle C, a tone the black hole has kept for two billion years. Astronomers believe these waves act as a brake on star formation, making the gas in the cluster too hot to condense into new stars.
Chandra astronomers recently “sonicated” these ripples by accelerating the signals to 57 or 58 octaves above the original pitch, increasing their frequency four times to make them audible to the human ear. As a result, the rest of us can now hear intergalactic sirens.
Through these new cosmic headphones, the Perseus black hole makes eerie clicking sounds that remind the listener of galumphing tones that refer to a strange radio signal that Jodie Foster hears through headphones in the sci-fi movie “Contact.”
As part of an ongoing project to “sonicate” the universe, NASA has also generated sounds generated similar to bright nodes in a jet of energy emanating from a supermassive black hole at the center of the giant galaxy known as M87. These sounds reach us across 53.5 million light-years as a majestic sequence of orchestral notes.
Another sonication project was undertaken by a group led by Irene Kara, an astrophysicist at MIT, as part of an effort to use light echoes from X-ray bursts to map the environment around black holes, much like using bats. Sound to catch mosquitoes.
It’s all the fruit of “Black Hole Week,” NASA’s annual social media extravaganza, May 2-6. As it happens this week, it provides a prelude to important news on May 12, when researchers using the Event Horizon Telescope, which in 2019 produced the first image of a black hole, announce their latest findings.
Black holes, according to Einstein’s general theory of relativity, are objects with a gravitational pull so strong that nothing, even light, let alone sound, can escape. Ironically, they can also be the brightest things in the universe. Before any kind of matter disappears forever into a black hole, theorists believe, it will be accelerated to near-light speeds by the hole’s gravitational field, heating up and spinning to millions of degrees. This will release X-ray flashes, generate interstellar shock waves, and compress high-energy jets and particles through space much like toothpaste from a tube.
In one common scenario, a black hole exists in a binary system with a star and steals material from it, which accumulates in a dense, bright disk–a visible donut of death–intermittently producing X-ray bursts.
Using data from a NASA instrument called the Neutron Star Interior Composition Explorer – NICER – a group led by Jinji Wang, a graduate student at MIT, searched for echoes, or reflections, of these X-ray bursts. The time delay between the original X-ray bursts and their reverberation and distortions caused by the strange gravitational proximity of black holes have provided insight into the evolution of these violent outbursts.
Meanwhile, said Dr. Kara works with education and music experts to convert X-ray reflections into audible sound. In some simulations of this process, she said, the flashes orbit the black hole, causing a distinct shift in their wavelengths before being reflected.
“I just love that we can ‘hear’ general relativity in this simulation,” Dr. Kara said in an email.
Eat your hearts out, Pink Floyd.