Solar system and comets. Illustration of the Solar System showing the planetary orbits and the paths of Halley's Comet (magenta) and Comet Ikeya-Zhang (green). From the nearest to the Sun outwards, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto (a dwarf planet). Comets are bodies of ice and dust, which move around the Sun in long, elliptical orbits. Halley's Comet is named after Edmund Halley (1656-1742), who first recognised its periodicity. It has been recorded every 76 years since 240 BC. Ikeya-Zhang is thought to orbit the Sun with a period of around 367 years.