Comet
A mass of rock and ice that orbits the Sun on a path that brings them close to the Sun at regular periods. When a comet nears the Sun it starts to vapourise, causing a 'tail' to form in a direction away from the Sun, blown by the Solar Winds. Some comets only orbit once before being completly blown away, some, like Halley's Comet every 76 years, repeat the journey on a regular basis.