Comet Ikeya-Zhang, optical image. This bright comet was visible in the northern hemisphere in spring 2002. Like most comets, it has two distinct tails. Its ion tail (blue) comprises glowing ionised gas blown away from the comet's head by the solar wind. Its dust tail (white) comprises grains of dust pushed away from the head by the radiation of sunlight. The dust tail shines by reflected sunlight only. Both tails always point away from the Sun, regardless of the comet's direction of travel. Ikeya-Zhang is thought to orbit the Sun with a period of around 367 years. Photographed from Finland on 1st April 2002.