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University of Toronto astrophysicists convert moons and rings of Saturn into music

August 30, 2017

Compositions provide a soundtrack for the Cassini probe’s final plunge into planet

Toron­to, ON –After cen­turies of look­ing with awe and won­der at the beau­ty of Sat­urn and its rings, we can now lis­ten to them, thanks to the efforts of astro­physi­cists at the Uni­ver­si­ty of Toron­to (U of T).

“To cel­e­brate the Grand Finale of NASA’s Cassi­ni mis­sion next month, we con­vert­ed Saturn’s moons and rings into two pieces of music,” says astro­physi­cist Matt Rus­so, a post­doc­tor­al researcher at the Cana­di­an Insti­tute for The­o­ret­i­cal Astro­physics (CITA) in the Fac­ul­ty of Arts & Sci­ence at U of T.

The con­ver­sion to music is made pos­si­ble by orbital res­o­nances, which occur when two objects exe­cute dif­fer­ent num­bers of com­plete orbits in the same time, so that they keep return­ing to their ini­tial con­fig­u­ra­tion. The rhyth­mic grav­i­ta­tion­al tugs between them keep them locked in a tight repeat­ing pat­tern which can also be con­vert­ed direct­ly into musi­cal har­mo­ny.

“Wher­ev­er there is res­o­nance there is music, and no oth­er place in the solar sys­tem is more packed with res­o­nances than Sat­urn,” says Rus­so.

The Cassi­ni space­craft has been col­lect­ing data while orbit­ing Sat­urn since its arrival in 2004 and is now in the throes of a final death spi­ral. It will plunge into the plan­et itself on Sep­tem­ber 15 to avoid con­t­a­m­i­nat­ing any of its moons.

Rus­so was joined by astro­physi­cist Dan Tamayo, a post­doc­tor­al researcher at CITA and the Cen­tre for Plan­e­tary Sci­ences at U of T Scar­bor­ough, and togeth­er they were able to play music with an instru­ment mea­sur­ing over a mil­lion kilo­me­ters long. The musi­cal notes and rhythms both come from the orbital motion of Saturn’s moons along with the orbits of the tril­lions of small par­ti­cles that make up the ring sys­tem.

“Saturn’s mag­nif­i­cent rings act like a sound­ing board that launch­es waves at loca­tions that har­mo­nize with the planet’s many moons, and some pairs of moons are them­selves locked in res­o­nances,” says Tamayo.

Music of the moons and rings

For the first piece which fol­lows Cassini’s final plunge, the researchers increased the nat­ur­al orbital fre­quen­cies of Saturn’s six large inner moons by 27 octaves to arrive at musi­cal notes. “What you hear are the actu­al fre­quen­cies of the moons, shift­ed into the human hear­ing range” says Rus­so. The team then used a state of the art numer­i­cal sim­u­la­tion of the moon sys­tem devel­oped by Tamayo to play the result­ing notes every time a moon com­pletes an orbit.

The moon sys­tem has two orbital res­o­nances which give rhyth­mic and har­mon­ic struc­ture to the oth­er­wise unsteady lul­la­by-style melody. The first and third moons Mimas and Tethys are locked in a 2:1 res­o­nance so that Mimas orbits twice for every orbit of Tethys. The same rela­tion­ship links the orbits of the sec­ond and fourth moons Encele­dus and Dione, and the com­bi­na­tion of the two sim­ple rhythms cre­ates inter­est­ing musi­cal pat­terns as they fall in and out of syn­chronic­i­ty.

“Since dou­bling the fre­quen­cy of a note pro­duces the same note an octave high­er, the four inner moons pro­duce only two dif­fer­ent notes close to a per­fect fifth apart,” says Rus­so, who is also a grad­u­ate of U of T’s Jazz per­for­mance pro­gram. “The fifth moon Rhea com­pletes a major chord that is dis­turbed by the omi­nous entrance of Saturn’s largest moon, Titan.”

Rus­so and Tamayo are joined in the project by Toron­to musi­cian, and Matt’s long-time band­mate, Andrew San­tagui­da. “Dan under­stands orbital res­o­nances as deeply as any­one and Andrew is a music pro­duc­tion wiz­ard. My job is to con­nect these two worlds.”

Titan actu­al­ly gives the Cassi­ni probe the final push which sends it hurtling towards its death in the heart of Sat­urn. The music fol­lows Cassini’s final flight over the ring sys­tem by con­vert­ing the con­stant­ly increas­ing orbital fre­quen­cies of the rings into a dra­mat­ic ris­ing pitch; the vol­ume of the tone increas­es and decreas­es along with the observed bright and dark bands of the rings. The death of Cassi­ni as it crash­es into Sat­urn is heard as a final crash of a final piano chord, which was inspired by The Bea­t­les’ “A Day in the Life”, in which a rich major chord fol­lows a sim­i­lar­ly tense crescen­do.

In addi­tion to the sound­track, Rus­so has had a large wood carv­ing made of Sat­urn’s rings so peo­ple can fol­low along with their fin­ger­tips while lis­ten­ing. The carv­ing will be part of a tac­tile-audio astron­o­my exhib­it at the Cana­di­an Nation­al Insti­tute for the Blind­’s Night Steps fundrais­ing event for the visu­al­ly impaired in Toron­to on Sep­tem­ber 15, the same day the Cassi­ni mis­sion is sched­uled to end.

Res­o­nances of Janus trans­lat­ed into music

The sec­ond piece demon­strates the scales played by Janus and Epimetheus, two small irreg­u­lar moons that share an orbit just out­side Saturn’s main ring sys­tem. Togeth­er they are an exam­ple of 1:1 res­o­nance, the only one in the solar sys­tem. The pair orbit at slight­ly dif­fer­ent dis­tances from Sat­urn but with a dif­fer­ence that is so neg­li­gi­ble they swap places every four years. The com­po­si­tion sim­u­lates the final few months of Cassini’s mis­sion, while Janus is inch­ing clos­er to Epimetheus before steal­ing its place in 2018. Togeth­er, the two moons play a uni­son drone but with a con­stant­ly shift­ing rhythm that repeats every eight years.

Rus­so played a C# note on his gui­tar once for every orbit while a cel­lo sus­tains a note for each res­o­nance with­in the rings.

“Each ring is like a cir­cu­lar string, being con­tin­u­ous­ly bowed by Janus and Epimetheus as they chase each oth­er around their shared orbit,” says Rus­so. Cassi­ni recent­ly cap­tured an image of one of the rip­ples this cre­ates with­in the rings. To turn this into music, Rus­so and San­tagui­da used the bright­ness vari­a­tions in this image to con­trol the inten­si­ty of the cel­lo.

“Saturn’s danc­ing moons now have a sound­track,” says Rus­so.

Rus­so, Tamayo and San­tagui­da are the same group who con­vert­ed the recent­ly dis­cov­ered TRAPPIST‑1 plan­e­tary sys­tem into music a few months ago. They’ve dubbed their astro-son­ic side-project SYSTEM Sounds and hope to con­tin­ue explor­ing the uni­verse for oth­er evi­dence of nat­u­ral­ly occur­ring har­mon­ic res­o­nance.

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Note to edi­tors:

Videos with audio for each of the pieces can be found on the SYSTEM Sounds web­site at, or indi­vid­u­al­ly at:

SATURN Sounds Part 1: Moons And Rings Trans­lat­ed Into Music —
SATURN Sounds Part 2: Res­o­nances Of Janus Trans­lat­ed Into Music —


Media con­tacts:

Matt Rus­so
Cana­di­an Insti­tute for The­o­ret­i­cal Astro­physics
Uni­ver­si­ty of Toron­to
+1 416 347 7157

Dan Tamayo
Cana­di­an Insti­tute for The­o­ret­i­cal Astro­physics
Uni­ver­si­ty of Toron­to
+1 647 331 9678

Sean Bet­tam
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to
+1 416 946 7950