Saturn’s invisible ring even larger than expected

Los Angeles Times : Saturn is known for its bright rings, but it also has a ring that can’t easily be seen. Called Phoebe, the ring is more than 10 times as wide as the next largest one. Phoebe was discovered in 2009 when Douglas Hamilton of the University of Maryland in College Park and his colleagues used NASA’s Spitzer Space Telescope, which observed Saturn in the IR, to look for the source of dust that coated one side of Saturn’s moon Iapetus. Hamilton and his team originally estimated that the ring sat between 7.7 million and 12.5 million km from Saturn. Now, using NASA’s Wide-field Infrared Survey Explorer, they have measured the ring’s thickness as well as the size of the material in it. The new location, between 6.0 million and 16.3 million km, puts it just beyond the orbit of the moon Phoebe, from which the ring gets its name. The team also estimates that 90% of the rocks in the ring are smaller than a soccer ball.