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Cassini Division

A narrow dark band in Saturn's ring system, seen from Earth as an apparently empty band between the outer A ring and the central B ring. The Cassini Division is 4,700 km across, and is not in fact the empty region that it appears. It contains matter like the other parts of the rings, but rather less densely spread, making it semi-transparent and thus dark against the background of space. This division in Saturn's rings is due to the gravitational influence of the inner moon Mimas, orbiting out beyond the edge of the A ring.

The Division contains finer structure of its own, including a sequence of narrow gaps within its own tenuous material. Two of these are more than 200km across: the Laplace Gap near the Division's outer edge, and the Huygens Gap close to its inner edge. Within the Huygens Gap is a yet smaller structure, a narrow band of denser material less than 20km wide, known as the Huygens Ringlet.


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