Halley's Comet. Halley's Comet orbits the Sun every 76 years. This periodicity was discovered by Edmund Halley (1654-1742), after whom the comet is named. Comets are balls of ice and dust form the solar system. Heat from the Sun evaporates the ice, forming a tail. This tail, which because of solar wind always points away from the Sun, can be many millions of kilometres long and very bright. Photographed from Melbourne Observatory, Australia on 18 April 1910.