Jahnavi Shah

M.Sc. Candidate, Geophysics & Planetary Science

Sound of Space

“There is geometry in the humming of the strings, there is music in the spacing of the spheres.” -Pythagoras

I recently came across One Sky after hearing some friends talk about their experience at Nuit Blanche Toronto. It was an outdoor musical planetarium exhibit, where the volume and pitch are controlled by the brightness and colour of the stars.

“Imagine walking into an empty field on a clear night, tilting your head up, and hearing the stars as you watch them appear one by one. Patterns begin to emerge and the constellations play their unique melodies as they dance across the sky. One Sky gives you that experience by converting the thousands of twinkling stars in the night sky into music.”

I thought it was really neat so I decided to look into its origin and found SYSTEM Sounds. It’s a collection of music and animations generated by numerical simulations and real data, created by Matt Russo (astrophysicist/musician), Dan Tamayo (astrophysicist), and Andrew Santaguida (musician). They were inspired by the musical TRAPPIST-1 planetary system and decided explore what happens when rhythms and harmonies of astronomical systems are translated into sound that humans can hear. 

For those who don’t know, TRAPPIST-1 is an exo-planetary system consisting of 7 Earth-sized planets orbiting a red dwarf and at least two planets should have the right temperature to host liquid water. But what’s more unique is that the planets are locked in a resonant chain, meaning the time it takes each planet to go around the star forms a simple, integer ratio ratio with those of its neighbours. For every 2 orbits of the outermost planet (h), each body (moving inward) executes 3, 4, 6, 9, 15 and 24 orbits. 

Actual orbital periods and corresponding frequencies and notes for each planets, after scaling orbital frequencies into the human hearing range.

Translation

REBOUND, an orbital integrator, was used to simulate the TRAPPIST-1 system and record the times when each planet passes in front of the star (transit) from the Earth’s point of view. Then time was scaled such that TRAPPIST-1h completes its orbit once every 2 seconds, corresponding to a tempo of 30 bpm. Next, orbital frequencies were scaled into human hearing range in order to calculate pitch; Time was sped up by about 212 million times so that TRAPPIST-1h completes its orbit 130.81 times each second (130.81 Hz), corresponding to the note C3. The frequencies of the interior planets were calculated based on the simple, integer ratio relation to this frequency. The TRAPPIST beat was created by assigning drum to conjunctions of each adjacent pair of planets. The gravitational tug between planets is greatest when a faster innner planet overtakes its outer neighbour (mutual conjunction). Lastly, data from NASA’s K2 mission monitoring the brightness of TRAPPIST-1 was used to capture the sound of the star! The star’s 3.3 day rotation period corresponds to a frequency of 745 Hz (after speeding up time by the same factor used to assign pitches to planets). There are many higher frequencies  also present due to the star’s variability and occasional solar flare. In addition, the star’s brightness variations data was used to modulate the volume of this noise so that it is louder when the star is brighter. The brightness/volume peaks occur almost 6 times for every orbit of TRAPPIST-1h (just as in real life). So now let’s actually listen to TRAPPIST Sounds:

Because TRAPPIST-1 planets are in resonance with its neighbours, the system forms a harmonic resonant chain. Most planetary systems don’t have this and so when their motion is converted into sound, it’s not as pleasing. 

The last thing I want to share is the Saturn Harp which was created by converting 2 million pixels of Cassini’s highest resolution colour image of the intricate patterns found within the central B ring into musical notes (brighter rings producing higher pitches). 

I found this project very exciting and I think the purpose is to help us experience our musical universe. 

Learn more: Our Musical Universe – TEDxUofTConvergent migration renders TRAPPIST-1 Long Lived

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