Planets’ Gravity Dance in Orbital Resonance

Planets orbit their parent stars at vast distances. For instance, in our solar system, planets are akin to grains of sand in a football field-sized region. The time for planets to complete their orbits around their suns does not have a specific relationship to each other.

Sometimes, however, their orbits exhibit remarkable patterns. For example, astronomers studying six planets orbiting a star 100 light years away found that they orbit their star in almost perfect synchrony, completing their orbits in times that are the ratios of whole numbers, allowing the planets to align and exert a gravitational push and pull on each other during their orbit—a phenomenon known as orbital resonance, resembling a harmony between distant planets.

Over the past 30 years, researchers have discovered over 5,600 exoplanets, and their incredible diversity continues to astonish astronomers.

Greek mathematician Pythagoras, 2,500 years ago, discovered the principles of musical harmony by analyzing the sounds of blacksmiths’ hammers and plucked strings. He proposed that the sun, moon, and planets each emit unique hums based on their orbital properties, which he called the “music of the spheres.”

Four hundred years ago, Johannes Kepler proposed that musical intervals and harmonies described the motions of the six known planets at the time, reflecting their orbital times around the sun. However, planets do not actually produce sounds since sound cannot travel through the vacuum of space.

Orbital resonance occurs when planets or moons have orbital periods that are ratios of whole numbers. This resonance is observed in only 5% of planetary systems. In the solar system, Neptune and Pluto are in a 3:2 resonance, and there is a triple resonance, 4:2:1, among Jupiter’s three moons: Ganymede, Europa, and Io. Musical intervals describe the relationship between two musical notes, such as the fourth, 4:3, the fifth, 3:2, and the octave, 2:1.

Orbital resonances can change how gravity influences two bodies, causing them to speed up, slow down, stabilize on their orbital path, or even have their orbits disrupted.

Exoplanets show striking examples of resonance, not just between two objects but also between resonant “chains” involving three or more objects. However, resonant chains are rare, and only 1% of all planetary systems display them, with most resonance chains eventually disappearing due to gravitational nudges from passing stars and wandering planets.

Astronomers have applied sonification, a technique that translates visual data into sound, to convey the mathematical relationships of exoplanets’ orbits. This approach offers a different way to appreciate the beauty of images from the Hubble Space Telescope and has been applied to X-ray data and gravitational waves as well.

Author: OpenAI