You can’t hear a black hole screaming in space, but you can obviously hear it singing.
In 2003, astrophysicists working with NASA’s Chandra X-ray Observatory discovered a wave 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 in diameter and emitted through the thin, ultra-hot gas that filled galaxy clusters. They are caused by periodic explosions of a supermassive black hole in the center of a bowl 250 million light-years away that contains thousands of galaxies.
With an oscillation period of 10 million years, the sound waves are acoustically equivalent to B-flat 57 octaves below the average C, a tone that the black hole has apparently maintained for the past two billion years. Astronomers suspect that these waves act as a brake on star formation, keeping the gas in the bowl too hot to condense into new stars.
Chandra’s astronomers recently “sonified” these waves, speeding up signals to 57 or 58 octaves above their original height, increasing their frequency by quadrillion times to make them audible to the human ear. As a result, the rest of us can now hear the intergalactic sirens singing.
Through these new space headphones, Perseus’ black hole emits eerie moans and rumbles that remind the listener of the glaring tones of an alien radio signal that Jody Foster hears through headphones in the science fiction film Contact.
As part of an ongoing project to “unify” the universe, NASA has also released similarly generated sounds from bright nodes in a stream of energy emanating from a giant black hole at the center of a huge galaxy known as M87. These sounds reach us at a distance of 53.5 million light years as a majestic series of orchestral tones.
Another sonication project was undertaken by a team led by Erin Kara, an astrophysicist at the Massachusetts Institute of Technology, as part of an effort to use light echoes from X-ray bursts to map the environment around black holes like bats. sound to catch mosquitoes.
All this is the result of “Black Hole Week”, an annual NASA social media extravaganza, May 2-6. As it happens, this week is a prelude to the big news on May 12, when researchers with the Event Horizon telescope, which created the first image of a black hole in 2019, have to announce their latest results.
Black holes, as Einstein’s general theory of relativity states, are objects with such strong gravity that nothing, not even light, much less sound, can escape. Paradoxically, they can be the brightest things in the universe. Before any matter disappears forever in a black hole, theorists suggest, it will be accelerated to speeds close to light, from the gravitational field of the hole, and will be heated, swirling, to millions of degrees. This will cause X-rays, generate interstellar shock waves, and squeeze high-energy jets and particles into space like a tube of toothpaste.
In a 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 doom – that sporadically produces X-ray bursts.
Using data from a NASA tool called the Neutron Star Interior Composition Explorer – NICER – a group led by Jingyi Wang, an MIT student, sought echo or reflection of these X-ray explosions. The time delay between the original X-ray explosions and their echoes and distortions caused by their proximity to the strange gravity of black holes gave an idea of the evolution of these violent outbursts.
Meanwhile, Dr. Kara is working with educational and music experts to convert X-ray reflections into sound. In some simulations of this process, she said, lightning travels all the way around a black hole, generating a treacherous shift in its wavelengths before being reflected.
“I just like that we can ‘hear’ the general theory of relativity in these simulations,” Dr. Kara said in an email.
Eat your hearts, Pink Floyd.
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