1. COMETS BY Owen Keupp

2. STRUCTURE Comets are made up of four component parts; the nucleus, coma, hydrogen envelope, and the tail. Nucleus- the main solid body which is just a few kilometers in diameter. During most of orbit it is the only thing existing. Made up of ice and debris. Coma-when it comes close to the sun it melts into dust and evaporated gas. Approximately 1000000 kilometers in diameter. Hydrogen envelope- approximately millions of kilometers in diameter and engulfs the coma. Most of the hydrogen envelope you cannot see. Tail- there are two types of tails. Ion tails- straight composed of glowing linear streamers and lines of ionized molecules, such as carbon monoxide, nitrogen, and water. Dust tails-broad spread out and curvy. They are made up of dust particles the reflect light

3. Haleys comet The most common periodic comet and can currently be seen every 75 to 76 years. Only short period comet that is clearly visible to the naked eye and that passes once a lifetime. Been recorded by astronomers since 240 b.c. but was not realized as a periodic comet until the eighteenth century when its orbit was observed by edmond hally. 1986 it was the second comet to be visited by a spacecraft.

4. Collisions Some comets smash into planets or other space debris.

6. Orbits Most break up when they near the sun. If they survive the survive this close encounter their speed increases and the will go all the way out to Pluto where their orbit slows down dramatically. The long period comets Take hundreds of thousands or millions of years to complete a full orbit. For short period comets their orbits last about 200 years, and they originate just outside of Neptune's orbit in the kuiper belt. There is another region a lot further out where most long term comets come from which hold trillions of comets and this is called the oort cloud.

7. Cool facts The word comet comes to the english language from the latin word cometes or the greek word kome, meaning “hair of the head”. Aristotle first used the derivation kometes to depict comets as “the stars with hair”.