Making Sweet Planetary Music at NAM Hack Day 2014


I’ve been in Portsmouth this week at the RAS National Astronomy Meeting.  The weather has been extremely pleasant – bagged lunches on the steps of the Guildhall were very pleasant, as Bob Nichol notes:

I gave a quick 8 minute talk in the “IMF: Facts and Myths” session on the properties of brown dwarfs – those awkward objects that are too small to be stars, but too big to be planets.  These in-betweeners turn out to be a very sensitive probe of planet formation theories, and observing the mass distribution of brown dwarfs should tell us whether they are more starlike than planetlike (more on that in a future post).

Alongside my usual conference activities, I took part in the first ever NAM hack dayHack days are an opportunity for programmers and like-minded people to spend a day creating something useful or fun from scratch.  “Hack” is the operative word here – throwing together something in a few hours is never that polished 🙂

My effort was inspired by Pythagoras’ musica universalis, or “music of the spheres”.  Pythagoras, and others like him, were convinced that there was a deep relationship between mathematical concepts and music.  Music theory depends heavily on mathematics, but Pythagoras believed that mathematics itself was inherently musical, and that the Universe moved to a deeply beautiful set of rhythms and harmonies.  For example, he believed the motions of the planets produced a music that, if humans could hear it, they would not only consider it beautiful, but discover a deeper understanding of how the Universe worked.

So, I thought about the music in planetary systems.  We have the benefit of knowing many more planets than Pythagoras did, orbiting stars other than our Sun.  Even for a musical dunce like myself, it’s easy to create musical notes from the properties of planets.  And that’s exactly what I did for my hack: I took exoplanet data from the Open Exoplanet Catalogue, and made repeating notes for each planet.  The period of the planet’s orbit dictates how frequently a note is played.  If a planet orbits its star once a year, then its note will play once per second.  The pitch of the note is determined by the planet’s size – small planets play a high pitched tone, and large planets play a low pitched tone.

So here’s what the Solar System sounds like as a song (headphones recommended for the full bass experience):


The inner planets orbit the Sun quickly, and make a series of high pitched ringing sounds, with the giant planets beating out a slow, ponderous bass line.

The code I wrote to make this music is open-source on Github – you can find it here.  It’s written in Python, and has a reasonable user interface (remember it’s a work in progress!).  Happy music making!

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