This illustration shows the size of a large, nearly invisible ring around Saturn (enlarged in this representation) that was detected by its infrared glow by the Spitzer Space Telescope (Image: NASA/JPL-Caltech/Keck)
A colossal ring of debris found around Saturn is the largest in the solar system. The new ring could be the ‘smoking gun’ that explains the curious two-faced appearance of Saturn’s moon Iapetus, whose leading hemisphere is much darker than its trailing side.
Until now, the biggest known planetary rings in the solar system were Saturn’s E ring and faint, gossamer sheets of dust orbiting Jupiter. Saturn’s E ring, a diffuse disc of icy material fed by the moon Enceladus, extends from 3 to perhaps 20 times the radius of Saturn.
The newly discovered ring spans from 128 to 207 times the radius of Saturn – or farther – and is 2.4 million kilometres thick. It was found using NASA’s Spitzer Space Telescope, which revealed an infrared glow thought to come from sun-warmed dust in a tenuous ring.
The discovery was announced on Tuesday at a meeting of the American Astronomical Society’s Division of Planetary Sciences in Fajardo, Puerto Rico. “This is a unique planetary ring system, because it’s the largest planetary ring in the solar system,” team leader Anne Verbiscer of the University of Virginia in Charlottesville told the meeting.
Although the ring is large, it is quite diffuse, making it difficult to detect using visible light. “It’s so faint ….
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Journal reference: Nature (DOI: 10.1038/nature08515)