Video: NASA's black hole audio shows how scientists are recording the universe

Analyzing the science, misconceptions, and future of astronomical sound.
Sade Agard
Universe starscape sound wave stock photo.
Universe starscape sound wave stock photo.


Ever wondered what the universe sounds like? While the Hubble space telescope has brought us a wealth of starry sights since its discovery in 1990, astronomical researchers have also been hooked on providing a means for people to experience these cosmic marvels using other senses too. In this case, it's our sense of hearing.

A brief history of astronomical discovery - thanks to sound

Video: NASA's black hole audio shows how scientists are recording the universe
NASA’s Cassini spacecraft above Saturn's northern hemisphere.

Scientists have been successful in several unexpected early discoveries aided by listening. For instance, Donald Grunett was the first researcher to make conscious attempts to document the sonification of space science data. For 50 years (1962 to 2012), he used sound to analyze and convey information returned by radio and plasma wave instruments from the space missions such as Cassini and Voyager.

More so, in 1964, researchers A. Penzias and R. Wilson experienced a disturbance, or "crackle," while performing observations with an antenna. They detected that the persistent noise during their study was due to the cosmic microwave background radiations- this discovery provided a boost in evidence for the Big Bang theory of the universe.

And that's not all. A more recent example is when sonification techniques identified a problem affecting the Voyager 2 space mission. The "machine gun" noise heard due to high-speed collisions led to the discovery of electromagnetically-charged micrometeoroids.

Sonification in brief

We know that space is a vacuum. Therefore, unlike on Earth, where vibrating air molecules exist for sound to travel through, matter in space is spread out very thinly, too thinly for sound to travel between the stars and planets. So then, where do these sounds really come from?

Well, sound sonification doesn't necessarily directly connect to the phenomena itself. Instead, it's a technique for representing information and data using non-speech audio.

The case of NASA's black hole- a controversy debunked

Video: NASA's black hole audio shows how scientists are recording the universe
Artist's impression of a black hole.

Take the recent release of NASA's sonification of a black hole 200 million light years away, for example. The "cosmic horror," as described by one Reddit user, has since gone viral and left the vast majority of those who listened to it pondering their own existence. It's also a prime example of how misconceptions about astronomical sonification can be fuelled when the background context of the science is not fully disclosed.

This particular sonification has been the source of some controversy on Twitter. We know that the black hole, in this case, is in the Perseus galaxy cluster, which is an 11 million-light-year-wide grouping of galaxies enveloped in hot gas. Decades ago, scientists from NASA's Chandra X-ray Observatory discovered that the black hole was sending out pressure waves.

These waves caused ripples in the cluster's hot gas, the data from which could then be translated into a note. But that's not the full story. "It is not the case that we could hear anything if we were to visit Perseus cluster." Dr. Christopher Harrison, an observational astronomer from the University of Newcastle, explains to IE.

Harrison further adds, "there are "sound waves" in the gas in the physics definition, but these are not audible to the human ear. The team has used the data to make an audible sound."

This then begs the following question; if we can't hear these sounds in their original form, then what are we listening to in NASA's new black hole sonification?

Simply put, the latest black hole sonification is actually a "remix" of these original non-audible sound waves. Scientists have resynthesized the waves so that they fall into the range of human hearing. That is, by scaling them upward by 57 and 58 octaves above their true pitch. According to NASA's website, they have been changed to a whooping 144 quadrillion and 288 quadrillion times higher than their original frequency. Bare in mind that a quadrillion has 15 zeros. Now that's quite the manipulation.

'Sonifying' data from some of NASA's grandest telescopes- what else can we 'hear' from space?

Video: NASA's black hole audio shows how scientists are recording the universe
The Hubble telescope with Earth in the background.

A new project known as "Data Sonification" is being led by the Chandra X-ray Center (CXC) as part of NASA's Universe of Learning (UoL). This involves a team of experts working to "sonify," or turn into sound, data from NASA's Chandra X-ray Observatory and the Hubble Telescope.

The data captured by telescopes come in binary code, ones and zeroes. These are usually translated into visual representations of objects which would otherwise be invisible to the naked eye. In the case of data sonification, the same digital data that gets translated into images is transformed into sound.

"None of this is directly listening to objects in space. Sonification is about taking data from telescopes and then deciding how to represent this data with sound. We should be careful not to confuse these two things," adds Dr. Christopher Harrison.

In the case of the sonification of Hubble images, the digital frequency data can be linked to a number of sound characteristics, for example, pitch, volume, timbre, etc. Pitch (a description of frequency - how high or low the sound is) is the most commonly used auditory dimension, given humans remember pitch relationships (e.g., melodies) better than volume or timbre relationships. One can immediately recognize the difference between the sound of a trumpet and flute, even if played at the same note (frequency), at the same loudness and duration.

NGC 1569 Starburst Galaxy (VIDEO)

NGC 1569 is one of the most active galaxies in our cosmic neighborhood. This starburst galaxy creates stars at a rate 100 times faster than our galaxy, the Milky Way! Scientists represented information using a Hubble image with sound to create a sonification with a bottom-to-top scan. Brighter light is higher pitched and louder. The three color channels used to process this image are each given a pitch range, with red representing lower pitches, green in medium pitches, and blue in high pitches.

Credits: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and A. Aloisi (STScI/ESA); Sonification: SYSTEM Sounds (M. Russo, A. Santaguida)

The Butterfly Nebula (VIDEO)

This spectacular Hubble image of the Butterfly Nebula shows a colorful view of star death. The "wings" of the butterfly are regions of gas heated to more than 36,000 degrees Fahrenheit (about 20,000 degrees Celcius) that are tearing across space at more than 600,000 miles an hour- that's 966,000 kph.

The vertical position is mapped to pitch – meaning that light towards the top of the image is higher pitched. The nebula is played on strings and synthetic tones, while a digital harp represents the stars. Brightness controls the volume, and the tilted hourglass orientation of the nebula produces an overall rising motion, with the prominent iron-rich jet producing a quick rise near the center.

Supernova 1987A (VIDEO)

On February 24, 1987, observers in the southern hemisphere saw a novel object in the Large Magellanic Cloud- a small satellite galaxy to the Milky Way. It turns out that this was one of the brightest supernova explosions in centuries and soon became known as Supernova 1987A. A timelapse was produced using a series of observations taken between 1999 and 2013 from Chandra X-ray Observatory (blue) and Hubble Space Telescope (orange and red).

The Supernova 1987A timelapse begins with a dense ring of gas. This is an ejection by the star before it becomes a supernova. As the ejection glows brighter with the progression of the supernova shockwave and the focus sweeps around the image, data are converted into a crystal singing bowl sound. Brilliant light is heard as higher and louder notes. The visible-light data are converted to a higher range of notes than the X-ray data, so both wavelengths of light can be heard simultaneously.

Potential benefits of sound for astronomical research, education and


Research has demonstrated that humans process audible information more quickly than visual information. Therefore, it makes sense that interpreting scientific data through sound could be more effective. We also know that the ear can distinguish more pitches over a broader range than the eye can distinguish colors. Think, if a picture is worth a thousand words, then its sound could be worth much more.

In August, Dr. Chris Harrison and colleagues published a study highlighting that sonification in astronomy is a recipe for more educational and public engagement. The study pinpoints that the motivation for the roll-out of this technique is not only to make astronomy more engaging but also to make the subject more accessible to visually impaired people.

Better yet, the study revealed that since 1996, there has been an increase in the number of known sonification and sound design astronomy projects. Around 8 to 19 new projects have been launched each year since 2016.

Also revealed is that sonification in astronomy could help us intuitively and comprehensively explore "noisy" and multidimensional datasets- a task relevant to the "big data" astronomy is well known for.

As humans, we naturally perceive several sounds simultaneously, meaning that we can listen to different "sonified" streams at the same time, and our hearing can single out one of these. Harrison and colleagues describe this as the "cocktail party effect." This is particularly relevant to astronomy with its "noisy" and multidimensional datasets.

"This is an ability we could look to exploit if we want to explore astronomical datasets: by listening to the data rather than looking at the data, we may be more effective and discovering information of interest," explains Dr. Christopher Harrison. Like at a party, we can tune in to one "voice" of interest in a room with lots of voices.

A space sound album- yay or nay?

Talking about parties, could we look forward to an album of space sounds one day, perhaps?

A project called "Black Hole Symphony" is doing this already. However, what you won't find is "sounds of space," where a microphone records directly from space.

An untapped astronomical resource tool

Whilst there has been an increase in the number of known sonification and sound design astronomy projects since 1996. That is, around 8 to 19 new projects have been launched each year since 2016. Sound-based techniques have yet to be incorporated into mainstream research tools.

This could be partly due to the lack of high-quality training and familiarity with sonification as a technique in astronomical research.

"Rather than making something that sounds nice, performing studies in the best approach to turn data into sound," explains Dr. Christopher Harrison. "This would involve producing something and then evaluating how effectively it achieves your goals with participants. How good are the participants at finding the signals in the data with sound?" Harrison adds.

According to the study, new solutions could be investigated, such as using sound filters to distinguish the signal from the noise.

"I can see big utility for future researchers being able to explore their data using their ears (rather than just their eyes) and for the general public, school children, etc. having a new and engaging way to learn about astronomy," shares Dr. Chris Harrison to IE.

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