Another cool sequence of images of shadows as Saturn approaches its northern spring equinox in just a few months. This time, we see the shadow of the moon Epimetheus moving across the outer A ring. The wide gap is the Encke Gap, about 330 km across, while the narrow gap near the outer edge of the ring is the Keeler Gap (about 30 km across). Epimetheus shares an orbit with the moon Janus. They each orbit Saturn roughly 6 times for every 7 orbits of a particle at the outer edge of the A ring. This orbital resonance between the moons and the ring edge controls the structure and evolution of the edge.
As equinox approaches, the shadows will get longer, and we will start to see shadows cast by warps and distortions within the rings themselves. NASA’s full press release is here.
