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 October 13
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

Giant Dust Ring Discovered Around Saturn
Credit: NASA/JPL-Caltech/Univ. of Virginia

Explanation: What has created a large dust ring around Saturn? At over 200 times the radius of Saturn and over 50 times the radius of Saturn's expansive E ring, the newly discovered dust ring is the largest planetary ring yet imaged. The ring was found in infrared light by the Earth-trailing Spitzer Space Telescope. A leading hypothesis for its origin is impact material ejected from Saturn's moon Phoebe, which orbits right through the dust ring's middle. An additional possibility is that the dust ring supplies the mysterious material that coats part of Saturn's moon Iapetus, which orbits near the dust ring's inner edge. Pictured above in the inset, part of the dust ring appears as false-colour orange in front of numerous background stars.

Tomorrow's picture: dust in the wind

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