Matt Russo, post-doctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA)
mrusso@cita.utoronto.ca

Astronomers and philosophers since as far back as Kepler and Pythagoras have imagined what the music of the spheres would sound like. With the discovery of seven Earth-sized planets orbiting in the nearby TRAPPIST-1 planetary system, this becomes possible as never before. Aside from being a prime target in the search for life, the TRAPPIST-1 planets are interesting because they form the longest discovered resonant chain. This means that the ratios of the planets' orbital periods form simple whole number ratios. For example, for every two orbits of the outer planet, the next one in completes three orbits and similar patterns exist among the orbits of every pair in this system. Since whole number ratios are the basis of rhythm and harmony, TRAPPIST-1 may be the most musical planetary system ever discovered.

To find out, I teamed up with Dan Tamayo, a fellow post-doc at the CITA and Andrew Santaguida, a fellow musician and bandmate. We used a realistic numerical simulation of the TRAPPIST-1 system to play a note for every time a planet transits in front of the star. To assign pitches we simply multiplied the orbital frequencies by about 212 million to bring them into the human hearing range. With this scaling, the outer planet plays a C note and the remaining planets fill out a rich but slightly out of tune Cmaj9 chord. We then played a drum for every time a faster inner planet overtakes its outer neighbour. Not wanting to leave the star of the band out, we sped up the observed brightness variations of TRAPPIST1-a to create a mysterious, crackling sound.

The result is a surprisingly human planetary rocker which highlights the many connections between astronomy (gr. 9 Science), waves and vibrations (gr. 11 physics), orbital motion (gr. 12 physics) and astrophysics (gr. 12 Earth and Space Science). Watch the video:



Find more information at http://www.system-sounds.com/

Tags: Astronomy, Waves and Sound