Orbital resonance
Resonance happens when
planets or moons have
orbital periods
that are
ratios of whole numbers
. The orbital period is the time taken for a planet to
make one complete circuit of 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 in only
5% of planetary systems
.
In the solar system, Neptune and Pluto are in a 3:2 resonance. There's also a
triple resonance
, 4:2:1, among Jupiter's three moons: 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 happen to have orbital periods that are the ratio of whole numbers.
Musical intervals describe the relationship between two musical notes. In the musical analogy, important
musical intervals
based on ratios of frequencies are the fourth, 4:3, the fifth, 3:2, and the octave, 2:1. Anyone who plays the
guitar or the piano
might recognize these intervals.
