See the amazing moon inside Saturn's rings

Illustration for article titled See the amazing moon eminside/em Saturns rings

This tiny little fellow is Daphnis, a moon that's just five miles wide and located inside a small gap in Saturn's rings. This image is the clearest shot yet of Daphnis and the warping effects it's having on the rings.

Daphnis was first discovered in 2005. It slots into the Keeler Gap, a 26-mile wide rift in one of Saturn's outer rings. Saturn's rings are 175,000 miles in diameter, which is about 3/4 the distance from the Earth to the Moon. Although the rings appear continuous in most images of Saturn, they are actually composed of countless pieces of ice and dirt that can be anywhere from a few particles to the size of a small town. Daphnis is the second moon found within a gap between the rings, with the 16-mile wide Pan the first to be discovered.

Both Daphnis and Pan are "shepherd moons", and indeed they take their names from mythological figures associated with shepherds. Shepherd moons are so named because they control the borders of the rings and maintain clearly defined edges in the same way that a shepherd herds his flock into an orderly shape. The gravity of these moons keeps most of the pieces of the ring in place, and anything wanders into their wake either gets deflected back, ejected into space, or merged with the moon.


That said, this image taken by the Cassini spacecraft also shows another side to Daphnis's gravitational control. Much as it works to keep the overall ring borders smooth, you can also see the disturbances it causes to the areas of the ring directly around it. These gravity ripples extend both horizontally and vertically, although obviously the horizontal components are far more easily visible in the image.


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Que Enya. It's so cute! And its orbit only varies by 9 kilometers from Saturn. It's like a boat on a track in an amusement-park ride ("It's a big gas giant after all, it's a big gas giant after all...").