Our Solar System

The Sun
	Every morning, the Sun rises in the east, bringing a new day. Ancient people thought of the Sun as a god. However, we know that it is actually a star, a blazing ball of gas that gives out light and heat. Without the light and heat from the Sun, there would be no life on Earth.

The Sun is huge, over 1,400,000km in diameter. This is more than one hundred Earths in a line next to each other. However, the Sun is only a very average star in size and brightness, it just looks bigger and brighter than the stars that we can see at night because it is so much closer. The Sun has a surface temperature of 5,500° and core temperature of 15,000,000°, so it is just as well that it is 150,000,000km from the Earth.

The Sun's boiling surface is marked with dark patches called sunspots. The number of sunspots rises and falls in an eleven year cycle. No one knows why they occur, but we do know that sunspots are the coolest areas of the solar surface. The coolest part of a sunspot looks quite dark and has a temperature of about 4,000°, 1,500° cooler than the brighter surface around them. A typical sunspot is many times larger than the Earth. They often occur in groups and can stretch for more than 100,000km across.

From time to time, huge explosions called flares occur near sunspots. In a few minutes, a flare releases as much energy as millions of hydrogen bombs and fires atomic particles into space at high speeds. These particles reach the Earth after a day or two where they bombard the upper atmosphere and cause colourful nighttime glows known as aurorae.

A Warning