Comet Hyakutake. Comet Hyakutake (1996 B2, lower centre) with a display of the northern lights or aurora borealis. Comets are formed from a ball of ice and dust only a few km across. When they approach the Sun some of the ice melts & is blown away by high-velocity charged particles from the Sun to form a tail. The tail is visible due to the reflection of sunlight by dust and discharges by excited gases. Charged particles from the Sun also cause the aurora borealis. They become trapped by the Earth's magnetic field and are drawn to the poles where they excite atmospheric atoms. The atoms' energy is released as light. Photographed in Alaska, USA on 15.4.96.