|Tehty: 10.11.2000||Arvosana: -|
|Sivuja: 1 kpl||Sanamäärä: 300|
|Tekijä: Jarmo Vestola|
Our Sun is a star, it contains more than 99.8% of the total mass of the Solar System, Jupiter contains most of the rest. The distance between the Sun and the Earth is nearly 150 million kilometres, so it takes 8.5 minutes for sunlight to reach the Earth. If you could fly to the Sun in a modern jet plane, it would take you nearly 20 years.
The Sun is over a million times bigger than the Earth. If the Sun was the size of a football, the Earth would be the size of the dot. Conditions at the Sun's core are extreme. The temperature is 15 million Kelvin and the pressure is 250 billion atmospheres. On the surface of the Sun, called photosphere, the temperature is some 6 thousand Kelvin, but Sunspots are only around half of that (3800 K) Sunspots are cool regions and look dark only by comparison with the surrounding regions. They can be very large, as much as 50 000 km in diameter.
The Sun is about 4.5 billion years old gigantic ball of burning gases. It is composed mainly of gas hydrogen. Nyclear reactions at the core of the sun change hydrogen into helium and generate massive heat. Since its birth it has used up about half of the hydrogen in its core. It will continue to radiate "peacefully" for another 5 billion years or so. But eventually it will run out of hydrogen fuel. The Sun will then be brighter, cooler and bigger -- a red giant star. Ultimately all sources of energy production will come to an end and the Sun will collapse to become a very small hot object called a white dwarf, which will result in the total destruction of the Earth.