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For other uses, see Commensurability (disambiguation).Commensurability is the property of two orbiting objects, such as planets, satellites, or asteroids, whose orbital periods are in a rational proportion.
Examples include the 2:3 commensurability between the orbital periods of Neptune and Pluto, the 3:4 commensurability between the orbital periods of the Saturnian satellites Titan and Hyperion, the Kirkwood Gaps in the asteroid belt, and the 2:1 commensurability between the extrasolar planets Gliese 876b and Gliese 876c.
Commensurabilities are believed to result from orbital resonance effects.