Observatory

) Asteroids (

About four and half billion years ago, our solar system was one big huge cloud of gas and rocks, which was slowly moving together under the influence of gravity. As the material compressed together in the centre, the surrounding gas and rocks started to form into other separate lumps. It was from these that our solar system was formed, with the central mass forming the sun and the separate lumps forming the planets which would encircle the sun. However, there was some material left over, which formed the comets and asteroids which threaten and amaze us today.

Asteroids can be classified according to size. A simple division is between the big asteroids and the small meteorites. The latter are very common with over 50,000 colliding with the Earth each year. Most of these smaller asteroids burn up in the atmosphere. The big asteroids could cause more devastation. In the Solar System, there is a band of asteroids 300 million miles from the Sun, called the asteroid belt. If an asteroid from elsewhere crosses this belt, it stands a chance of knocking itself and one of the large asteroids off course, changing its orbit. There is always the possibility that either could head for Earth.

On November 17th, 1998, one of the most spectacular firework displays ever seen will occur. The Leonids meteor shower will stretch across the skies for over an hour as the Earth passes by the comet Temple-Tuttle.

Links

NASA Featuring comet footage
Leonids Information on November 17th's spectacle

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