Hear the strange sounds of a singing black hole

In space, you can’t hear a black hole scream, but apparently you can hear it sing.

In 2003, astrophysicists working with NASA’s Chandra X-ray Observatory in orbit 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 in diameter and radiating outward through the thin, ultra-hot gas that permeates 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 B-flat 57 octaves below middle C, a pitch 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 cluster too hot to condense into new stars.

Chandra astronomers recently “sonified” these ripples by accelerating the signals to 57 or 58 octaves above their original pitch, raising their frequency quadrillions of times to make them audible to the human ear. As a result, the rest of us can now hear the intergalactic siren song.

Thanks to these new cosmic headphones, the black hole of Perseus makes strange moans and growls it reminded this listener of the galloping tones marking an alien radio signal that Jodie Foster hears through headphones in the science fiction film “Contact”.

As part of an ongoing project to “sonify” the universe, NASA has also released similarly generated images. sounds of glowing nodes in a jet of energy firing 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 in the form of a majestic succession of orchestral sonorities.

Another sonification project has been undertaken by a group led by Erin Kara, an astrophysicist at the Massachusetts Institute of Technology, as part of an effort to use the bright echoes of X-ray bursts to map the environment around black holes. , just like bats use sound to catch mosquitoes.

This is all a consequence of “Black Hole Week,” an annual NASA 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 holemust announce their latest results.

Black holes, as Einstein’s theory of general relativity decrees, are objects whose gravity is so strong that nothing, not even light, much less sound, can escape from them. Paradoxically, they can also be the brightest things in the universe. Before any sort of matter would ever disappear into a black hole, theorists speculate it would be accelerated to near-light speeds by the hole’s gravitational field and heated, swirling, to millions of degrees. It would trigger X-ray flashes, generate interstellar shock waves, and squeeze high-energy jets and particles into space like so much 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 in a dense, shiny disk – a visible donut of doom – which sporadically produces bursts of X-rays.

Using data from a NASA instrument called Neutron Star Interior Composition Explorer – NICER – a group led by Jingyi Wang, an MIT graduate student, searched for echoes or reflections from these X-ray bursts. The delay between the original X-ray bursts and their echoes and distortions caused by their proximity to the strange gravity of black holes has provided insight into the evolution of these violent explosions.

During this time, Dr. Kara worked with education and music experts to convert X-ray reflections into audible sound. In some simulations of this process, she said, the lightning flashes all the way around the black hole, causing a telltale change in their wavelengths before being reflected.

“I love that we can ‘hear’ general relativity in these simulations,” Dr Kara said in an email.

Eat your heart, Pink Floyd.