Six Alien Planets Have Been Found Locked in a Rare, Complex Orbital Dance
8 FEBRUARY 2021
A planetary system 200 light-years away has been found locked in a rare orbital dance. Of the six exoplanets orbiting a star named TOI-178, the five outermost follow rhythmic orbital periods, with each linked to the planets on either side.
Such a dance is called a chain of resonance, and it s only rarely seen. But it can reveal something about how planetary systems form.
Orbital resonances aren t uncommon. Basically, they mean that the orbital periods of two bodies can be described as a ratio.
A few examples can be found in the Solar System. There s Pluto and Neptune - for every two orbits of Pluto around the Sun, Neptune goes around thrice; that s a 2:3 resonance. And three moons of Jupiter are in a resonance chain. For every one orbit of Ganymede, Europa goes around twice and Io four times; that s a 1:2:4 resonance.