Just how “locked” are resonant-chains of exoplanets thought to be?

2017-12-15 07:16:46

The Phys.org news item Discovery of new planet reveals distant solar system to rival our own outlines the recent announcement of results using AI to help search Kepler photometric (transit-method) data for exoplanets. Near the end is the paragraph:

Kepler-90i wasn't the only jewel this neural network sifted out. In the Kepler-80 system, they found a sixth planet. This one, the Earth-size Kepler-80g, and four of its neighboring planets form what is called a "resonant chain," where the planets are locked by their mutual gravity in a rhythmic orbital dance. The result is an extremely stable system, similar to the seven planets in the TRAPPIST-1 system, so precisely balanced that the length of Kepler-80g's year could be predicted with mathematics.

My question is about these "resonant-chains" of planets. If I understand correctly this would be a group of planets where due to mutual perturbative effects they are in orbits who's periods are in mutual rational number ratio