Comet Hale-Bopp. Optical image of comet Hale-Bopp showing its gas and dust tails. It was one of the brightest comets of the 20th century. The comet's gas or ion" tail (blue) consists of ionised glowing gas blown away from the comet head by the solar wind. The dust tail (white) consists of grains of dust pushed away from the comet head by the radiation of sunlight. A comet's tails always point away from the Sun and these tails may be millions of kilometres in length. Comet Hale-Bopp was discovered on 23 June 1995. It is seen in the constellation Cygnus, with the red North America nebula (NGC 7000) at upper right."