Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2017 February 22
Daphnis and the Rings of Saturn 
 Image Credit: NASA, JPL-Caltech, Space Science Institute, Cassini Explanation: What's happening to the rings of Saturn? Nothing much, just a little moon making waves. The moon is 8-kilometer Daphnis and it is making waves in the Keeler Gap of Saturn's rings using just its gravity -- as it bobs up and down, in and out. The featured image is a wide-field version of a previously released image taken last month by the robotic Cassini spacecraft during one of its new Grand Finaleorbits. Daphnis can be seen on the far right, sporting ridges likely accumulated from ring particles. Daphnis was discovered in Cassini images in 2005 and raised mounds of ring particles so high in 2009 -- during Saturn's equinox when the ring plane pointed directly at the Sun -- that they cast notable shadows.