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Explained: NASA’s sonification project that turns astronomical images into music

What is data sonification? How did NASA translate astronomical images into sound? Why is this sonification project useful?

By: Explained Desk | New Delhi |
Updated: September 25, 2020 2:45:45 pm
nasa, nasa sonification project, astronomical images, nasa astronomy, nasa news, indian expressNASA’s Chandra X-Ray Center (CXC) has gone a step further by unveiling a new ‘sonification’ project that transforms data from astronomical images into audio. (Screengrab: NASA/Youtube)

While telescopes offer glimpses of outer space by translating digital data into stunning images, NASA’s Chandra X-Ray Center (CXC) has gone a step further by unveiling a new ‘sonification’ project that transforms data from astronomical images into audio.

Users can now ‘listen’ to images of the Galactic Centre, the remains of a supernova called Cassiopeia A, as well as the Pillars of Creation Nebula, which are all located in a region around 26,000 light years away from Earth. The data has been collected by NASA’s Chandra X-Ray Observatory, Hubble Space Telescope and Spitzer Space Telescope — each of which is represented by a different musical ‘instrument’.

What is data sonification?

Data sonification refers to the use of sound values to represent real data. Simply put, it is the auditory version of data visualisation. In NASA’s recent Chandra project, for instance, data is represented using a number of musical notes. With this data sonification project, users can now experience different phenomena captured in astronomical images as an aural experience. The birth of a star, a cloud of dust or even a black hole can now be ‘heard’ as a high or low pitched sound.

How did NASA translate astronomical images into sound?

NASA’s distant telescopes in space collect inherently digital data, in the form of ones and zeroes, before converting them into images. The images are essentially visual representations of light and radiation of different wavelengths in space, that can’t be seen by the human eye.

The Chandra project has created a celestial concert of sorts by translating the same data into sound. Pitch and volume are used to denote the brightness and position of a celestial object or phenomenon. So far, the astronomers behind Project Chandra have released three examples made using data collected from some of the most distinct features in the sky — the Galactic Centre, Cassiopeia A, and Pillars of Creation Nebula.

The Galactic Centre

The first example is that of the Galactic Centre, which is the rotational centre of the Milky Way galaxy. It comprises a collection of celestial objects — neutron and white dwarf stars, clouds of dust and gas, and most notably, a supermassive black hole called Sagittarius A*, that weighs four million times the mass of the sun.
Based on data gathered by the Chandra X-ray Observatory, and the Hubble and Spitzer Space Telescopes, an image is rendered using X-ray, visible and infrared light before being translated into sound. The translation begins on the left side of the image and then moves to the right. Stars and other compact sources are represented using individual short notes, while a longer humming sound is used to denote clouds of gas and dust. It all builds up to a crescendo, which takes place around the bright region to the lower right of the image where Sagittarius A* is located.

Cassiopeia A

Located around 11,000 light years away from Earth in the northern Cassiopeia constellation, Cassiopeia A is one of the most well-known remnants of a once-massive star that was destroyed by a supernova explosion around 325 years ago, according to NASA. The image shows the supernova remnant as a ball of different coloured filaments. Each colour represents a particular element — red is used for silicon, yellow for sulfur, purple denotes iron, while green is used for calcium. Each of these filaments is also assigned its own unique sound.

Unlike with the sonification of the Galactic Centre, where the translation plays from left to right, here the sounds move outwards from the centre of the circular structure.

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The Pillars of Creation

The iconic Pillars of Creation is located in the centre of the Eagle Nebula, which is also known as Messier 16. The Hubble Star Telescope was used for images of the celestial structure, which comprises wispy towers of cosmic dust and gas. Here too, different colours are used to represent elements — blue for oxygen, red for sulphur and green for both nitrogen and hydrogen.

Like with the Galactic Centre, this sound translation also plays from left to right. However, the sound has an eerie effect, with sharp whistles representing stars and low howls indicating the presence of gas clouds. A user has the option of listening to all three images at once as an ensemble, where each telescope plays a different instrument, or individually as a solo, NASA stated in a recent blog post.

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Why is this sonification project useful?

The sonification project was led by the Chandra X-ray Center in collaboration with NASA’s Universe of Learning Program (UoL), which aims to “incorporate NASA science content into the learning environment effectively and efficiently for learners of all ages”. Over the years, NASA has been working towards making data about space accessible for a larger audience. According to a statement released by team Chandra, sonification projects like this allow audiences — including visually-impaired communities — to experience space through data.

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