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The Solar System

The Planets - Asteroids and Meteors.

There is a belt of asteroids between the orbits of Mars and Jupiter.
Asteroids are small rocky objects,
often with a high hydrocarbon content.
They are sometimes called the "minor planets".

The belt contains many thousands of asteroids.
The large majority are less than 100km in diameter.
A small number have diameters of 200km to 500km.
The largest observed so far is approximately 1000km in diameter.

If an asteroid enters the Earth's atmosphere it is called a meteor.
Meteors become intensely hot as they move through the atmosphere.
They are travelling extremely fast and make a large number
of collisions with molecules in the air.
This is a form of friction and generates a great deal of heat.

Small meteors burn up in the upper atmosphere
and can be seen as a streak of light in the night sky.
These are sometimes called "shooting stars".

Large meteors can sometimes survive the journey through
the atmosphere and fall all the way to the Earth's surface.
They may hit the Earth at great speed and some have caused
huge craters. A meteor which hits the Earth is called a meteorite.

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