In our galaxy there are tens of millions of black holes. We know that almost all galaxies with masses similar to that of the Milky Way or even higher harbor supermassive black holes in their nucleus, in the heart of the galaxy.
Black holes, despite being invisible to our eyes, release X-rays in the process of increasing mass as they feed (for example, when a black hole draws in dust and gas from a nearby orbiting star), and these X-rays can be reflected in the material around the black hole creating bursts that briefly illuminate a black hole’s surroundings; it is what astronomers call “echoes”. The spooky frictional and gravitational interactions involved in the process generate intense heat and light, causing the region around the black hole to glow. Now, for the first time ever, a team of scientists has turned these “echoes” from black holes into sounds, and…unsurprisingly , they are truly eerie sounds.
They’re hard to spot, but…
A team of astronomers from the Massachusetts Institute of Technology (MIT) is analyzing the echoes from such systems to reconstruct the extreme and immediate neighborhood of a black hole. In their study, published in The Astrophysical Journal, the scientists talk about using a ” reverberation machine ” to search satellite data for signs of echoes from black holes.
The astrophysicists collected data from NASA’s NICER telescope, an X-ray telescope mounted on the outside of the International Space Station, to learn about the evolution of black holes as they feed on nearby stars. And precisely eight new black hole binaries with echoes have been found in our galaxy thanks to the Neutron star Interior Composition Explorer (NICER). Those eight binary systems contained a black hole, with a binary companion star that the black hole gradually stripped away and devoured.
“We see new reverberation signatures in eight sources,” explains astrophysicist Jingyi Wang of MIT. “Black holes range in mass from five to 15 times the mass of the Sun, and all are in binary systems with normal, low-mass Sun-like stars.”
“The role of black holes in the evolution of galaxies is an outstanding question in modern astrophysics,” MIT astrophysicist Erin Kara, a co-author of the study, explained in a press release. “Interestingly, these black hole binaries appear to be ‘mini’ supermassive black holes , and so by understanding outbursts in these small nearby systems, we can understand how similar outbursts in supermassive black holes affect the galaxies in which they reside.”
Starting up the ‘reverberation machine’
In parallel, together with a group of education and music scholars at MIT, they have been working to convert the emission of an X-ray echo from a black hole into audible sound waves. Low frequency light became lower pitches and high frequency light became higher pitches. The results, which you can hear in the video that accompanies this article, offer a rather creepy effect worthy of a horror movie.
“We are at the beginning of being able to use these light echoes to reconstruct the closest environments to the black hole,” Kara continued. ” We have now shown that these echoes are commonly observed , and we can probe the connections between a black hole’s disk, jet, and corona in a new way.”
Referencia: Jingyi Wang, Erin Kara, Matteo Lucchini, Adam Ingram, Michiel van der Klis, Guglielmo Mastroserio, Javier A. García, Thomas Dauser, Riley Connors, Andrew C. Fabian, James F. Steiner, Ron A. Remillard, Edward M. Cackett, Phil Uttley, Diego Altamirano. The NICER “Reverberation Machine”: A Systematic Study of Time Lags in Black Hole X-Ray Binaries. The Astrophysical Journal, 2022; 930 (1): 18 DOI: 10.3847/1538-4357/ac6262
