Ultraviolet and infrared images from NASA's Cassini spacecraft and Hubble Space Telescope show active and quiet auroras at Saturn's north and south poles.
Saturn's auroras glow when energetic electrons dive into the planet's atmosphere and collide with hydrogen molecules. Sometimes a blast of fast solar wind, composed of mostly electrons and protons, creates an active aurora at Saturn, as occurred on April 5 and May 20, 2013.
The first set of images, as seen in the ultraviolet part of the spectrum by Hubble, shows an active aurora dancing around Saturn's north pole on April 5. The movie then shows a relatively quiet time between April 19 to 22 and between May 18 and 19. The aurora flares up again in Hubble images from May 20. This version, shown in false-color, has been processed to show the auroras more clearly.
A second set of ultraviolet images shows a closer view of an active north polar aurora in white. This set comes from Cassini ultraviolet imaging spectrograph observations on May 20 and 21.
The last set of images, in the infrared, shows a quiet southern aurora (in green) in observations from Cassini's visual and infrared mapping spectrometer on May 17. Saturn's inner heat glows in red, with dark areas showing where high clouds block the heat.
Image credit: NASA/JPL-Caltech/University of Colorado/Central Arizona College and NASA/ESA/University of Leicester and NASA/JPL-Caltech/University of Arizona/Lancaster University