Equinox

Description

Saturn, a gas giant planet with an extensive ring system, is over 120,000 kilometres across. Equinoxes occur every 15 Earth years (twice every Saturn year) when the Sun passes directly overhead at the planet’s equator. This results in the ring system casting a narrow shadow on the planet (visible here), as opposed to the broader shadow cast on one of the hemispheres at other times of the year. This mosaic includes the moon Mimas (lower left) and brightening of the rings to make them more visible. The images were obtained on 4 September 2009, by the wide-angle camera on the orbiting Cassini spacecraft. (Photo by Science Photo Library)