Aurorae on Jupiter. Hubble Space Telescope compos- ite coloured ultraviolet image of aurorae in the atmosphere around Jupiter's north and south magnetic poles (inset on planet). The aurorae are mainly white, whilst reflected sunlight appears brown. Jupiter's aurorae occur when charged particles are trapped by the planet's magnetic field and collide with its atmosphere. These collisions make the gas glow like a fluorescent lamp. The charged particles mainly come from volcanic eruptions on Jupiter's moon Io. Image taken by Hubble's Space Telescope Imaging Spectrograph (STIS) instrument on 20 September 1997.