Astronomy Picture of the Day

Explanation: How should Cassini say farewell to Saturn? Three days before plunging into Saturn's sunny side, the robotic Cassini spacecraft swooped far behind Saturn's night side with cameras blazing. Thirty-six of these images have been merged -- by an alert and adept citizen scientist -- into a last full-ring portrait of Cassini's home planet for the past 13 years. The Sun is just above the frame, causing Saturn to cast a dark shadow onto its enormous rings. This shadow position cannot be imaged from Earth and will not be visible again until another Earth-launched spaceship visits the ringed giant. Data and images from Cassini's mission-ending dive into Saturn's atmosphere on September 15 continue to be analyzed.