Orbital resonance: planets have a gravitational dance with aligned orbits| Trending Viral hub


The planets orbit their parent stars being separated by enormous distances; In our solar system, the planets are like grains of sand in a region the size of a football field. The time it takes for planets to orbit their suns has no specific relationship to each other.

But sometimes their orbits show surprising patterns. For example, astronomers who study six planets orbiting a star 100 light years away, they have just discovered that they orbit around their star with an almost rhythmic rhythm, in perfect synchrony. Each pair of planets completes their orbits in times that are whole number ratios, allowing the planets to align and exert a gravitational push and pull on each other during their orbit.

This type of gravitational alignment is called orbital resonanceand it is like a harmony between distant planets.

I am a astronomer who studies and writes about cosmology. Researchers have discovered more than 5,600 exoplanets in the last 30 years, and its extraordinary diversity continues to surprise astronomers.

Harmony of the spheres

greek mathematician Pythagoras He discovered the principles of musical harmony 2,500 years ago by analyzing the sounds of blacksmiths’ hammers and plucked strings.

He believed that mathematics was at the heart of the natural world and proposed that the Sun, Moon, and planets emitted unique hums based on their orbital properties. He thought that this “music of the spheres” would be imperceptible to the human ear.

Four hundred years ago, John Kepler picked up this idea. He proposed that musical intervals and harmonies described the movements of the six planets known at the time.

For Kepler, the solar system had two bases, Jupiter and Saturn; a tenor, Mars; two tall ones, Venus and Earth; and a soprano, Mercurio. These roles reflected how long it took each planet to orbit the Sun, lower speeds for the outer planets and higher speeds for the inner planets.

He called the book he wrote on these mathematical relationships “The harmony of the world.” While these ideas have some similarities to the concept of orbital resonance, planets do not actually make sounds, since they Sound cannot travel through the vacuum of space..

Orbital resonance

Resonance occurs when Planets or moons have orbital periods that are proportions of whole numbers. The orbital period is the time it takes for a planet to make one complete revolution around the star. So, for example, two planets orbiting a star would be in a 2:1 resonance when one planet takes twice as long as the other to orbit the star. Resonance is seen only in 5% of planetary systems.

Orbital resonance, as seen in Jupiter’s moons, occurs when the orbits of planetary bodies align; For example, Io orbits Jupiter four times in the time it takes Europa to orbit twice and Ganymede once. WolfmanSF/Wikimedia Commons

In the solar system, Neptune and Pluto are in a 3:2 resonance. There is also a triple resonance, 4:2:1, between the three moons of Jupiter: Ganymede, Europa and Io. In the time it takes Ganymede to orbit Jupiter, Europa orbits twice and Io orbits four times. Resonances occur naturally, when planets have orbital periods that are the ratio of integers.

Musical intervals describe the relationship between two musical notes. In the musical analogy, important musical intervals Based on frequency ratios they are the fourth, 4:3, the fifth, 3:2, and the octave, 2:1. Anyone who plays the the guitar or the piano could recognize these intervals.

Musical intervals can be used to create scales and harmony.


Orbital resonances can change how gravity influences two bodies, causing them to accelerate, decelerate, stabilize in their orbital path, and sometimes interrupt their orbits.

Think about pushing a boy on a swing. Both a planet and a swing have a natural frequency. Give the child a push that matches the movement of the swing and he or she will receive a boost. They will also get a boost if you push them every second time they are in that position, or every third time. But push them at random times, sometimes with the movement of the swing and sometimes against it, and they won’t get any boost.

Orbital resonance can cause planets or asteroids to accelerate or begin to wobble.


For planets, momentum may keep them continuing on their orbital paths, but it is much more likely to disrupt their orbits.

Exoplanet resonance

Exoplanets, or planets outside the solar system, show striking examples of resonance, not only between two objects but also between resonant “chains” involving three or more objects.

The star Glass 876 It has three planets with orbital period ratios of 4:2:1, as do Jupiter’s three moons. Kepler 223 It has four planets with proportions of 8:6:4:3.

the red dwarf Kepler 80 It has five planets with ratios of 9:6:4:3:2, and TOI 178 It has six planets, of which five are in a resonant chain with ratios of 18:9:6:4:3.

TRAPPISTA-1 is the record holder. He has seven Earth-like planets, two of which could be habitablewith orbital ratios of 24:15:9:6:4:3:2.

The most recent example of a resonant chain is the HD 110067 system. It is about 100 light years away and has six sub-Neptune planets, a common type of exoplanet, with orbital ratios of 54:36:24:16:12:9. The discovery is interesting because most resonance chains are unstable and disappear over time.

Despite these examples, resonant strings are rare and Only 1% of all planetary systems show them.. Astronomers believe that planets form in resonance, but small gravitational nudges from passing stars and wandering planets erase the resonance over time. With HD 110067, the resonant chain has survived for billions of years, offering a unique and pristine view of the system as it was when it formed.

Orbit sonification

Astronomers use a technique called sonification translate complex visual data into sound. Gives people a different way to appreciate the beautiful images of the Hubble space telescopeand has been applied to X-ray and gravitational wave data..

In the case of exoplanets, sonification can transmit the mathematical relationships of their orbits. Astronomers at the European Southern Observatory created what they call “music of the spheres”for the TOI 178 system associating a sound in a pentatonic scale to each of the five planets.

Music of planetary orbits, created by astronomers from the European Southern Observatory.


TO similar musical translation has been done for the TRAPPIST-1 system, with the orbital frequencies increased by a factor of 212 million to bring them into the audible range.

Astronomers have also created a sonification for the HD 110067 system. People may not agree on whether these interpretations sound like real music, but it’s inspiring to see Pythagoras’ ideas realized after 2,500 years.


Chris Impey is a distinguished professor of astronomy at the University of Arizona. This article is republished from The conversation under Creative Commons License. Read the Original article.


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