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 6 May 1910.