Credit: NASA/JPL/Space Science Institute

NASA recently published an astounding image of Saturn, the ringed wonderful planet. The image, acquired by the Saturn-bound Cassini spacecraft, shows the night side of Saturn (approximately 120,000 km across). In this image, Saturn shines merely as a bright arc, extending from the top to the bottom of the image, as the Sun is on the other side of Saturn. Saturn is only illuminated by feeble sunlight, scattered in the upper layers of the planet’s dense dynamic atmosphere.
This amazing illumination of Saturn was observable due to the position of Cassini relative to Saturn and the Sun. The Sun-Saturn-Cassini angle was 172 degrees, meaning the spacecraft was on the dark side of the planet, at the time the image was obtained. The night in Saturn lasts approximately 5 hours.
The immense shadow of Saturn is cast upon the planet’s graceful rings, at middle right in the image. Just below the center of the image the light reflected by Saturn is obscured by the B ring, the most massive of the rings. (Saturn’s major rings received English alphabetical designation, in order of discovery.)
As the Sun is now shining above the plane of the rings, the shadow of the rings is projected onto the lit side of the planet, near the bottom middle of the image.
The spacecraft was looking on the northern, sunlit side of the rings, from just above the plane of the rings. The image was taken in green light, with the Cassini spacecraft wide-angle camera, on 13 February 2010. Cassini was at a distance of approximately 373,000 km from Saturn.
Further Reading
The Cassini Mission Homepage
http://saturn.jpl.nasa.gov/index.cfm

Aymen Mohamed Ibrahem
Senior Astronomy Specialist