The planet Saturn, shown here in a 2007 image from the Cassini spacecraft, rotates rapidly, so a "day" on the giant world lasts only about 10 or 11 hours. Because Saturn is made of gas, however, locking down that number is difficult. Astronomers use different techniques to measure the length of a day, producing varying estimates. [NASA/JPL/SSI]
Find out more in our radio program entitled Moon and Saturn.