Spectacular details of the auroral curtains of ultraviolet light around Saturn's north and south poles have been observed for the first time by the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. The photograph (right), released last week, was taken in October, when Saturn was 1.3 billion km from Earth.
When used as a camera, the new instrument is more than ten times as sensitive as previous Hubble instruments in the ultraviolet. Saturn's auroral displays are caused by an energetic wind from the Sun that sweeps over the planet. Unlike Earth, Saturn's aurora is seen only in ultraviolet light invisible from the Earth's surface.