A musical visualization of the Trappist-1 planetary system

The Trappist-1 planetary system was discovered a few months ago, and immediately garnered a whole lot of buzz for having no less than seven Earth-sized planets, at least some of which appear to be in zones that could provide the conditions for life ("as we know it").

The system is less than 40 light years away from Earth, and revolves around a red dwarf star, which has been designated as Trappist-1. This star is much smaller and colder than our Sun, but its planets are much closer to it: all seven of the planets orbit within six million miles of the star, as compared to our own Solar System where Mercury, the closest planet to the Sun, has an orbit of 36 million miles, while Earth is over 93 million miles from the Sun. The closely-packed Trappist-1 planets therefore orbit very quickly, with "years" (the time taken to complete one orbit of the star) ranging from just 1½ days to 19 days.

The system also presented something of a mystery to astrophysicists, because when the planets' orbits were modelled on computer systems, even with the added effect of tides, the model systems always completely fell apart, usually within a just a few million years, while the Trappist-1 system is actually 3-8 billion years old.

Now, it had also been pointed out, quite early in the investigation of the system, that the planets exhibited what is known as "harmonic orbital resonance", which is a fancy way of saying that the orbits of the different planets have a whole number relationship with each other, similar to the relationships of notes in a musical harmonic scale. Thus, the second planet of Trappist-1 completes five orbits in almost exactly the time the first planet makes eight, the third planet completes three orbits for every five orbits of the second planet, the fourth planet makes two orbits for every three orbits of the third, etc. It is thought that it is these harmonic relationships that somehow allow the planets' orbits to stay stable for long periods of time, a veritable "music of the spheres".

This has led Matt Russo, an astrophysicist who is also a musician, to play around with the data and create a musical visualization of the planets' orbits by assigning musical notes to the different planets based on their orbital distances and periods. Different percussion sounds were also added for each time a planet caught up with its neighbour. The result is a little disconcerting, and the resonances do drift slightly over time (probably as a result of more complex gravitation and tidal effects), but it is actually surprisingly listenable.

Interestingly, this is the only system yet discovered where the planetary orbits are stacked in resonance. For example, when Russo tried a similar musical treatment of the Kepler-90 system, another star with seven planets, the results were "very uncomfortable to listen to". Perhaps Pythagoras, who first came up with the idea of the music of the spheres, had something after all.