Hyperion (moon)

Hyperion (hye-peer'-ee-un, Greek ????????) is a moon of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. It is distinguished by its irregular shape, its chaotic rotation, and its unexplained sponge-like appearance.

Rotation

The Voyager 2 images and subsequent ground based photometry indicate that Hyperion's rotation is chaotic, that is, its axis of rotation wobbles so much that its orientation in space is unpredictable. Hyperion is the only known moon in the solar system that rotates chaotically, but simulations suggest that other irregular satellites may have done so in the past.

Related Topics:
Voyager 2 - Photometry - Chaotic

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It is unique among the large moons in that it is very irregularly shaped, has a fairly eccentric orbit, and is near another large moon (Titan).

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These factors combine to restrict the set of conditions under which stable rotation is possible.

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The 3:4 orbital resonance between Titan and Hyperion may also make chaotic rotation more likely.

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The odd rotation probably accounts for the fact that the Hyperionian surface is more or less uniform, in contrast to many of Saturn's other moons which have contrastive leading and trailing hemispheres.

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