In 1999, astronomers discovered a star they called, quite unimaginatively, 2MASS J23062928-0502285 (These numbers refer to the right ascension and declination of the star’s position in the sky and the “J” refers to the Julian Epoch.). The star was later studied again and in 2015, a team found 3 planets orbiting around the star, followed by the discovery of another 4. The astronomers, led by the Belgian Michaël Gillon, used the TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) telescope for the initial discovery and subsequently named the solar system Trappist-1 (the Trappist also refers to the famous Belgian beers). Through careful observation of the star, they were able to detect the transits of the planets. Every time a planet passes in front of the star, it blocks a bit of the light, which is enough to detect the planet. With 500 hours of observation, the team was able to calculate the trajectories of the planets and create a simulation of the system.
The TRAPPIST system is special in the way all planets seem to be moving in simple ratios to each other.
Mapping
Andrew Santaguida, Matt Russo, and Daniel Tamayo created a sonification of the transits of each planet, by scaling the orbital frequencies to the human hearing range. That way, by speeding up the time by 212 million, Trappist-1h, which completes an orbit in 18,76 days, has a frequency of 130,81 Hz (roughly equal to C3). Because the other planets orbit in simple ratios, there is a consonant harmony. Tamayo made a short sonification of the Keppler90 system, a similar system with 7 planets but where the planets do not rotate in simple ratios and hence the melody sounds chaotic. He calls it, quite fitting, the anti-Trappist.
The second layer is made using a drum kit and neighbouring planet pairs: every time a planet ‘overtakes’ its neighbour planet, a drum sound is played.
45 seconds in the sonification, the notes are sustained and doubled one octave lower so that a beat pattern occurs. and a slightly out-of-tune Cmaj9 chord missing the 3d arises.
There is a third layer based on the brightness of the star. Using Kepler telescope’s K2 long cadence observations and using the same time-compression as with the planets, the creators ended with a noise with an average frequency of 745 Hz (roughly F#5). Because there are small variations in the speed and solar flares, the frequency is not stable and thick, noisy tone results. This sound is looped with the low frequency artifacts that occur because of the looping removed.
The brightness is also used for the volume of the noise: the brighter the star, the louder the noise.
You can read more on the dedicated website system-sounds.
Make your own version
The software used for this sonification is available for download and you can create your own version. You can also adapt it to use other datasets.
Other sonifications
NASA’s outreach team has also created a sonification and you can download the sonification sheet music, MIDI-files, and the video here and rework them in your own compositions.
Finally, Disquiet Junto is a group project on Soundcloud, where people can download the data and create their own composition. This group does other projects as well and is worth checking out.
For both of these projects, I will look for more information on the artists and update this post later on.
Sonification Art 