Comets

Comets are made up of a mixture of frozen water, gases and dust like dirty muddy ice balls. They are the remains of material that was left over after the formation of the solar system.

Comets are only visible when they are near the Sun in their very eccentric orbits. Their orbits are often tilted to the ecliptic and retrograde.

The solar wind blasts material off the comet leaving a visible dust tail. After 500 or so orbits the gas and water may have been blasted off and all that remains is the rocky nucleus, the comet is dead.

In 1705 Edmund Halley predicted, using Newton's new laws of motion, the reappearance of the comet now named after him. It has a period of 76 years last appearing in 1986. It appeared in 1066, an event which is depicted in the Bayeaux Tapestry. If you're lucky enough to be around in 2062 you will see it again.

Comets have been classified as short or long period depending on the orbit time.