The solar system's largest planetary ring is even more extensive than scientists thought. In 2009, the Spitzer Space Telescope discovered infrared radiation from a ring far beyond all the others encircling Saturn; sunlight heats the ring's dust, which emits its heat at infrared wavelengths. Now, as astronomers report online today in Nature, another heat-seeking spacecraft—NASA's Wide-field Infrared Survey Explorer—has detected this same ring, finding that it extends 6 million to 16 million kilometers from the planet. If Saturn were the size of a basketball, the ring from one side of the planet to the other would span two-thirds the length of a football field. Although the ring is huge, its dust particles are tiny. They probably arise when debris shed by comets hits distant saturnian satellites such as Phoebe, kicking up material that goes into orbit around the ringed planet.