Since 2003, the black hole at the center of the Perseus galaxy cluster has been associated with sound. This is because astronomers discovered that pressure waves sent out by the black hole caused ripples in the cluster's hot gas that could be translated into a note — one that humans cannot hear some 57 octaves below middle C. Now a new sonification brings more notes to this black hole sound machine. This new sonification — that is, the translation of astronomical data into sound — is being released for NASA's Black Hole Week this year.
In some ways, this sonification is unlike any other done before (1, 2, 3, 4) because it revisits the actual sound waves discovered in data from NASA's Chandra X-ray Observatory. The popular misconception that there is no sound in space originates with the fact that most of space is essentially a vacuum, providing no medium for sound waves to propagate through. A galaxy cluster, on the other hand, has copious amounts of gas that envelop the hundreds or even thousands of galaxies within it, providing a medium for the sound waves to travel.
In this new sonification of Perseus, the sound waves astronomers previously identified were extracted and made audible for the first time. The sound waves were extracted in radial directions, that is, outwards from the center. The signals were then resynthesized into the range of human hearing by scaling them upward by 57 and 58 octaves above their true pitch. Another way to put this is that they are being heard 144 quadrillion and 288 quadrillion times higher than their original frequency. (A quadrillion is 1,000,000,000,000,000.) The radar-like scan around the image allows you to hear waves emitted in different directions. In the visual image of these data, blue and purple both show X-ray data captured by Chandra.
Black Hole at the Center of Galaxy M87:
In addition to the Perseus galaxy cluster, a new sonification of another famous black hole is being released. Studied by scientists for decades, the black hole in Messier 87, or M87, gained celebrity status in science after the first release from the Event Horizon Telescope (EHT) project in 2019. This new sonification does not feature the EHT data, but rather looks at data from other telescopes that observed M87 on much wider scales at roughly the same time. The image in visual form contains three panels that are, from top to bottom, X-rays from Chandra, optical light from NASA's Hubble Space Telescope, and radio waves from the Atacama Large Millimeter Array in Chile. The brightest region on the left of the image is where the black hole is found, and the structure to the upper right is a jet produced by the black hole. The jet is produced by material falling onto the black hole. The sonification scans across the three-tiered image from left to right, with each wavelength mapped to a different range of audible tones. Radio waves are mapped to the lowest tones, optical data to medium tones, and X-rays detected by Chandra to the highest tones. The brightest part of the image corresponds to the loudest portion of the sonification, which is where astronomers find the 6.5-billion solar mass black hole that EHT imaged.
More sonifications of astronomical data, as well as additional information on the process, can be found at the "A Universe of Sound" website: https://chandra.si.edu/sound/
These sonifications were led by the Chandra X-ray Center (CXC) and included as part of NASA's Universe of Learning (UoL) program with additional support from NASA's Hubble Space Telescope/Goddard Space Flight Center. The collaboration was driven by visualization scientist Kimberly Arcand (CXC), astrophysicist Matt Russo, and musician Andrew Santaguida (both of the SYSTEMS Sound project). NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science from Cambridge Massachusetts and flight operations from Burlington, Massachusetts. NASA's Universe of Learning materials are based upon work supported by NASA under cooperative agreement award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.
Fast Facts for Perseus Cluster:
About the Sound:
- This is more than a data sonification, it's actually a re-sonification of a real sound wave
- Researchers identified literal sound waves in earlier images of this cluster (the lowest pitches ever found), we have extracted them and made them audible for the first time
- Waves propagating along each radial direction (and any periodic features) are extracted from the image, sweeping around 360 degrees
- Signals are resynthesized after scaling by 57 and 58 octaves above their true pitch, 144 and 288 quadrillion (million billion) times their true frequency, or about 7 piano-lengths
- The true pitch of the sound waves generated by the black hole is Bb, just over 57 octaves below middle C
- Waves were extracted from blue image here and here
- Purple image used for visualization (radar plus audio spectra)
- Sound contains the actual waves plus some signals from other large scale density fluctuations (such as cavities)
Category: Groups & Clusters of Galaxies, Black Holes
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30´ 37.00"
Constellation: Perseus
Observation Date: 25 pointings between Sep 1999 and Dec 2009
Observation Time: 416 hours 37 minutes (17 days 8 hours 37 minutes)
Color Code: X-ray: red = 0.5-1.2 keV, green = 1.2-2.0 keV, blue = 2.0-7.0 keV
Distance Estimate: About 240 million light years
Fast Facts for M87:
About the Sound:
- Left to right scan in which brightness controls volume
- The vertical position controls pitch
- Each wavelength is mapped to notes in a different pitch range
- Radio/optical/x-ray are mapped to low/med/high ranges (Following the ordering of their frequencies of light)
- Radio (ALMA) is played on a brass-like synth
- Optical (HST) is played on a breathy synth (sustained for diffuse gas, plucked for point-like star clusters)
- X-ray (Chandra) is played on string-like synth
- The most intense parts of the core and jet that appear white are also heard as pitch-filtered noise
- the core near the BH is the brightest/loudest
- rising jet with gaps and clumps can be heard as rising pitch with volume fluctuations
- Glow in HST due to billions of unresolved stars produces sustained chord
Category: Black Holes, Quasars & Active Galaxies
Coordinates (J2000): RA 12h 30m 49.40s | Dec +12° 23´ 28.00"
Constellation: Virgo
Observation Date: April 11, 2017 and April 14, 2017
Observation Time: 7 hours 17 minutes
Obs. ID: 20034, 20035
Instrument: ACIS
Color Code: Intensity
Distance Estimate: About 55 million light years
