Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2009 April 27
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Prometheus Creating Saturn Ring Streamers
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA

Explanation: What's causing those strange dark streaks in the rings of Saturn? Prometheus. Specifically, an orbital dance involving Saturn's moon Prometheus keeps creating unusual light and dark streamers in the F-Ring of Saturn. Now Prometheus orbits Saturn just inside the thin F-ring, but ventures into its inner edge about every 15 hours. Prometheus' gravity then pulls the closest ring particles toward the 100-km moon. The result is not only a stream of bright ring particles but also a dark ribbon where ring particles used to be. Since Prometheus orbits faster than the ring particles, the icy moon pulls out a new streamer every pass. Sometimes, several streamers or kinks are visible at once. The above photograph taken in mid-January by the robotic Cassini Spacecraft orbiting Saturn. The oblong moon Prometheus is visible on the far left of the image.

Tomorrow's picture: galaxy edge

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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