Listen to the Ghostly Howl of a Black Hole Echo

Date:8 May 2022 Author: Juandre

Researchers at MIT have found a way to simulate what light bouncing around a black hole sounds like.

When black holes gobble up the matter around them—often gas and dust from orbiting stars—they sometimes emit bursts of x-ray light that illuminate their edges. These bursts reverberate off of the encircling material and zip across the universe into awaiting instruments. The echoes can provide a wealth of data on what happens to the black hole during these outbursts of x-ray light.

A team of scientists at the Massachusetts Institute of Technology (MIT) have developed an automated search tool that could help astronomers identify these ghostly echoes emitted by a specific type of black hole; these are black hole x-ray binaries, or hungry black holes that feed on the stars orbiting around them. The team’s algorithm, which they dubbed the “Reverberation Machine,” pored through data collected by the Neutron Star Interior Composition Explorer, an x-ray telescope mounted to the International Space Station. They identified previously undetected echoes from black hole binary systems in our galaxy.

Of the 26 total black hole binaries the algorithm identified, ten are close enough to Earth to send audible echoes. Eight of these ten systems had not previously produced observable echoes before. The team published their findings this week in the Astrophysical Journal.

“We see new signatures of reverberation in eight sources,” Jingyi Wang, a graduate student at MIT and one of the study’s co-authors, said in a press release. “The black holes range in mass from five to 15 times the mass of the sun, and they’re all in binary systems with normal, low-mass, sun-like stars.”

These echoes can be extremely helpful to astronomers. For instance, similar to the way that bats use echolocation to hunt their prey and avoid obstacles, these echoes can help researchers pinpoint more precisely the location of the black hole’s edge. These echoes also shed light on how black holes behave and what types of materials they burp up during these x-ray outbursts.

What’s more, one of the study authors tapped a duo of education and music scholars at MIT to convert the x-ray echoes into an audible sound. Check out the ghostly moan below:

This certainly isn’t the first time we’ve developed a way to listen to our distant cosmic neighbors. Scientists have found ways to sonify gravitational waves produced during the cataclysmic collision of two black holes. And just this week, NASA released the remix of a data sonification made from the pressure waves emitted by a black hole at the center of the Perseus galaxy cluster, collected by the Chandra X-ray Observatory.

Here, researchers were able to create this sound using data from sound waves collected by the observatory. (Sound waves can, in fact, form in space when there’s enough media—like the gas and dust found in a galaxy cluster—for them to propagate through.) The ripples in the gas and dust caused by these waves translated into an imperceptible note roughly equivalent to 57 octaves below middle C, according to the agency. For the remix, the team scaled the note up to within an audible range.

Another famous black hole—you know, the extremely photogenic one at the center of M87 galaxy—is getting the audio treatment, too. Astronomers at the Smithsonian Astrophysical Observatory’s Chandra X-ray Center in Cambridge, Massachusetts, and several other institutions joined together to release a sonification of M87* built from x-ray data collected by Chandra, optical data gathered by Hubble, and radio waves collected by Chile’s Atacama Large Millimeter Array (ALMA).

In this case, each wavelength corresponds to a different set of audible tones, according to a NASA press release, with the highest tones representing Chandra’s X-ray data, middle tones representing data from Hubble, and the low tones representing data from the ALMA observatory.

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