Comets

A comet is a icy or rocky ball that lives in space. They vary in size and shape so they can be very small or very large (from a few hundred metres to a few kilometres). They can be made of all different substances.Comets are mostly made up of ice and dust with a bit of rock and maybe some organic carbon.Some other materials are water, dry ice, carbon,ammonia,methane and several common gasses. These are some of the materials that make up what we call comets.

Some comets make more than one visit. When some get close enough to the sun heat starts to evaporate them and jets of gas make it look like a long tail. And also when it gets close enough to the sun it makes itself a tiny thin atmosphere. And sometimes they crash into the big planets like (Jupiter, Saturn, Uranus and Neptune) or some passing stars. When all the gasses have gone it leaves just the rock which makes it a bit like a asteroid in appearance.

In the ancient times people used to think that it was a sign that something bad was going to happen to them. But the people didn't understand about movement in the sky. But with the technology these days we can explore more of the solar system and learn more about it.

Some famous comets are Halley's comet which comes through every 75 to 76 years. It was discovered in 1705 by an English astronomer Edmond Halley. And it may appear once or twice in a normal human lifespan. Others are comet Holmesand comet Hale-Bopp. The picture to the right is Halley's comet.

References and links: [|en.wikipedia.org/wiki/]**[|Comet]** [|www.questacon.edu.au/starlab/]**[|comet]**[|_info.html] [|www.windows2universe.org/]**[|comets]**[|/]**[|comets]**[|.html] [|nineplanets.org/]**[|comets]**[|.html]