text: Comets are hard, compact bodies of ice and dust that orbit the sun. Commonly found on eliptical orbits that take anything from a few years to thousands of years to complete. As a comet gets nearer to the sun a tail of gas becomes visible and appears longer nearer the sun.\n\nThe best known is Halley's comet and Hale-Bopp. The latter being clearly visible in the night sky over Britain about 10 years ago. Comet Hale-Bopp is very unusual in that it has two tails instead of the normal one.\n\nComets are remnants of the formation of the universe billions of years ago. Most comets originate in an area of space known as the Oort Cloud.