In space you can’t hear a black hole scream, but apparently you can hear it sing.
In 2003, astrophysicists working with NASA’s orbiting Chandra X-ray Observatory detected a ripple pattern in the X-ray glow of a giant cluster of galaxies in the constellation Perseus. They were pressure waves, that is, sound waves, 30,000 light-years across and radiating outward through the thin, ultra-hot gas that fills galaxy clusters. They were caused by periodic outbursts 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 pitch the black hole has apparently been maintaining for the past two billion years. Astronomers suspect that these waves act as a brake on star formation, keeping the gas in the cluster too hot to condense into new stars.
Chandra astronomers recently “sonified” these waves by accelerating the signals to 57 or 58 octaves above their original pitch, increasing their frequency quadrillions of times to make them audible to the human ear. As a result, the rest of us can now hear the song of intergalactic sirens.
Through these new cosmic headphones, Perseus’ black hole emits eerie wails and rumbles that reminded this listener of the galloping tones that mark an alien radio signal that Jodie Foster hears through headphones in the sci-fi movie “Contact Us.” “.
As part of an ongoing project to “sonify” the universe, NASA has also released similarly generated sounds from the glowing knots in a jet of energy shooting out from a giant black hole at the center of the gigantic galaxy known as M87. . These sounds reach us across 53.5 million light-years as a majestic succession of orchestral tones.
A group led by Erin Kara, an astrophysicist at the Massachusetts Institute of Technology, has undertaken another sonification project as part of an effort to use light echoes from X-ray bursts to map the environment around black holes, much like than bats. Sound to catch mosquitoes.
This is all a fallout from “Black Hole Week,” NASA’s annual social media extravaganza, from May 2-6. As it happens, this week provides a prelude to big news on May 12, when researchers at the Event Horizon Telescope, which in 2019 produced the first image of a black hole, will announce their latest results.
Black holes, as Einstein’s general theory of relativity decrees, are objects with such strong gravity that nothing, not even light, let alone sound, can escape. Paradoxically, they can also be the brightest things in the universe. Before any kind of matter disappears forever into a black hole, theorists suppose, the hole’s gravitational field would accelerate it to speeds close to the speed of light and heat it, swirling it, to millions of degrees. This would cause flashes of X-rays, generate interstellar shock waves, and squeeze high-energy jets and particles through space like toothpaste in a tube.
In a common scenario, a black hole exists in a binary system with a star and steals material from it, which accumulates into a dense, bright disk, a visible donut of doom, that sporadically produces bursts of X-rays.
Using data from a NASA instrument called the Neutron Star Interior Composition Explorer (NICER), a group led by Jingyi Wang, an MIT graduate student, searched for echoes, or reflections, of these X-ray bursts. the original X-ray bursts and their echoes and distortions caused by their proximity to the strange gravity of black holes offered insight into the evolution of these violent bursts.
Meanwhile, Dr. Kara has been working with education and music experts to convert X-ray reflections into audible sound. In some simulations of this process, she said, the flares travel all the way around the black hole, generating a telltale shift in their wavelengths before reflecting off.
“I love that we can ‘hear’ general relativity in these simulations,” Dr. Kara said in an email.
Eat your heart out, Pink Floyd.