Popular Astronomy

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The Sun

Image: Robin Scagell


Amazing fact!

Even though it is the closest star to Earth, the Sun is still a long way away – 149 million kilometres to be precise. The light it gives off takes over eight minutes to reach Earth, so we always see the Sun as it was eight minutes in the past!

But remember: NEVER look at the Sun with your eyes, or through a telescope, as it is so bright it can damage your eyesight permanently.

     The Sun is our closest star. It is like all the other stars we see in the night sky, expect they are all so far away that they only appear as points of light. The Sun, on the other hand, is much closer. It is at the centre of the Solar System, and all the planets, asteroids and comets orbit around it.
The Sun is the biggest object in the Solar System with a width of 1.4 million kilometres. It is made mostly of hydrogen gas (70 percent), with some helium gas (28 percent). The remaining two percent is made up of other gases. The temperature at its gaseous surface is 5,500 degrees Celsius. But if you think that’s hot, wait until you hear how hot it is in the middle of the Sun – a scorching 15 million degrees Celsius!
      The Sun generates energy by billions of natural nuclear bombs going off inside it every second. Because the pressure and the temperature are so high inside the Sun, the atoms of hydrogen are squeezed, or ‘fused’ together. This is called nuclear fusion, and in the process energy is released. The Sun produces 386 trillion trillion watts of energy every second. That’s the same amount of energy as is given out by 386 billion trillion 100-watt light bulbs! It is no wonder the Sun is so bright.
      Quite often, the Sun is covered in spots – sunspots! These are dark spots on the Sun’s surface that are cooler than the surrounding areas, so appear dark. Even so, they are still very hot, around 3,500 degrees Celsius.
      The Sun gives warmth and energy to planet Earth. Without it, there would be no life here. We are very lucky to have the Sun, but it won’t always be here. Far in the future, in about five billion years time, it will run out of atoms of hydrogen to make into helium in its natural nuclear explosions. At first, the Sun will swell up into a red giant, before throwing off its outer layers of gas. These outer layers will make a pretty nebula, but all that will be left of our dying Sun will be its hot core, which will become a white dwarf. When this happens, our descendents in the future will have to find somewhere else to live.

Sunspots can be much larger than the Earth!

Image: Dave Tyler