Aurorae happen when charged particles from the sun are ejected into space by a solar storm and then encounter the magnetic field of a planet. The charged particles create dazzling displays of color in the atmosphere that can be visible both from the surface and space.
Cassini captured the "ghostly curtains of light" in Saturn's atmosphere and overlaid it with an infrared photograph of Saturn taken in 2008. The colors in the video were digitally inserted afterwards.
"Some of the stars seem to make a slight turn to the right just before disappearing," said NASA officials in a statement. "This effect is due to refraction — the starlight gets bent as it passes through the atmosphere, which acts as a lens. Some of the stars seem to make a slight turn to the right just before disappearing. Random bright specks and streaks appearing from frame to frame are due to charged particles and cosmic rays hitting the camera detector."
Cassini fixed its camera into one spot for a full hour to observe the aurora. It swung low to get a better view, coming within 620,000 miles of Saturn's atmosphere.
Saturn's aurorae were discovered by the Pioneer 11 probe in the late 1970s. Since then, they've been studied by the Voyager probes, the Hubble Space Telescope, and Cassini.
The observation will be one of Cassini's last. The orbiter, which arrived at Saturn in 2004, has run out of fuel and will be purposefully destroyed in a dive towards Saturn on September 15.
