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What does Pluto’s 3:2 orbital resonance with Neptune mean?
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Pluto
Pluto as observed by the New Horizons spacecraft, July 13, 2015.
Pluto’s 3:2 orbital resonance with Neptune means that Pluto completes exactly two orbits around the Sun in the same amount of time it takes Neptune to complete three orbits.12
This gravitational interaction acts as a stabilizing mechanism for Pluto’s orbit. Although Pluto’s highly eccentric path brings it closer to the Sun than Neptune for a portion of its revolution, this resonance ensures that the two bodies never pass closer than approximately 17 astronomical units, preventing any possibility of a collision.2
In recognition of this shared orbital characteristic, other Kuiper belt objects that exhibit the same 3:2 resonance with Neptune are referred to as Plutinos.31