Halimede.space

Halimede’s wandering orbit

How the Sun reshapes a distant moon’s path.

Published 2026-10-23

Halimede is so far from Neptune that the Sun’s gravity significantly perturbs it.[1]

Averages

Over 10,000 years its semi-major axis averages about 16.59 million km, varying only from 16.55 to 16.63 million km.[1]

Big swings

Its eccentricity ranges from 0.19 to 0.90 and inclination from 111° to 145°.[1]

Lowest inclination

Halimede has the lowest average inclination of any known retrograde irregular moon — which actually means its orbit is highly tilted, about 60° from the ecliptic if you ignore direction.[1]

Precession

Its orbit precesses with periods of 5,395 and 5,156 years.[1]

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