Astrophysicists have created music out of the movements of Saturn's rings and moons in honor of spacecraft Cassini's final dive into the ringed planet.
The Cassini spacecraft is in the Grand Finale stage of its mission, in which the spacecraft is probably weaving in and out between Saturn and its rings. On September 15, 2017, Cassini will descend down to Saturn and into its intentional destruction. While Cassini has contributed a lot to scientific knowledge and likely holds a special place in the hearts of many, its destruction is necessary. Deorbiting the spacecraft will ensure that the spacecraft won't accidentally collide with and contaminate one of Saturn's moons.
“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 Mark Russo. Russo and his colleagues used orbital resonances in order to create the musical piece.
Orbital resonance refers to when two objects move through their orbits at different speeds, but return to their original positions at the same time. For example, Saturn's moon Mimas completes two orbits for every orbit that the moon Tethys completes. Two other moons, Enceladus and Dione, have the same pattern as well. Every time a moon completes an orbit, a note is played.
The researchers increased the orbital frequencies of six of Saturn's large moons by 27 octaves in order to turn them into musical notes that human ears can hear. The volume, meanwhile, increases or decreases according brightness and darkness of the ring bands.
“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. “The fifth moon Rhea completes a major chord that is disturbed by the ominous entrance of Saturn's largest moon, Titan.”
The musical piece pays homage to Cassini by following the spacecraft's flight over Saturn's rings. Russo and his colleagues converted the increasing orbital frequencies into a rising pitch, until Cassini's demise is heard as a resonant piano chord. This final chord was created with the combination of the oscillation frequencies of Saturn.
This musical homage isn't just an auditory experience. Russo also commissioned a large wood carving of Saturn's rings, which people can touch while listening to the music. With the aid of the carving, listeners can follow the notes and their progressions. The carving will be available at an astronomy exhibit at the Canadian National Institute for the Blind on September 15, the same day Cassini will deorbit.
The wood carving representing Saturn's moons and rings [Photo by SYSTEM Sounds]
And that's just the first piece—the team created a second piece of music as well, which is also an homage to Cassini and the end of its mission. This second piece features the moons Janus and Epimethus, both of which are locked with each other in a one-on-one orbital resonance. Their resonance is special in that it's the only one-on-one resonance in the entire solar system.
Russo and his colleagues have also created musical piece featuring the TRAPPIST-1 system. This piece is similar to the ones on Saturn's rings and moons.
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