HST Image of Saturn Moon Transits
This sequence of images captures the parade of several of Saturn's moons transiting the face of the gas giant planet. This is a rare event because the rings are tilted edge on to Earth every 15 years. The top frame captures the giant moon Titan and its shadow near Saturn's northern polar hood. Tiny Mimas and its shadow have just entered the left limb of Saturn, slightly above the rings. To the far left off the disk, Dione, the brightest of the icy moons in this view – and Enceladus, fainter and farther to the left – can easily be seen just above the rings. In the center frame, Dione and Enceladus can be seen near the western limb of Saturn, while Titan's shadow is off the limb, and Mimas is on the right most limb, its shadow also now off the limb. In the bottom frame, Dione and its shadow are centered above Enceladus and its shadow. Titan is now off the right limb. This picture sequence was taken with Hubble's Wide Field Planetary Camera 2 on February 24, 2009, when Saturn was at a distance of roughly 775 million miles (1.25 billion kilometers) from Earth. Hubble can see details as small as 190 miles (300 km) across on Saturn.