English Across the Curriculum

The Solar System

The Sun - Centre of the Solar System

The sun is a star at the centre of our solar system. It is a huge spinning ball of hot gas that lights up the Earth and provides us with heat. Our sun is a medium-sized yellow star that is about 150 million km away from the Earth.

Here are some important facts about our sun:

  • The sun is one of more than 200 billion stars in our galaxy, the Milky Way.
  • The Milky Way is one of billions of galaxies in our universe. There are as many galaxies, as there are stars in the Milky Way
  • The sun is 30,000 light years away from the centre of the Milky Way.
  • The sun is made up of over 70 % hydrogen, 27 % helium and other elements.
  • On the surface, the sun has a temperature of over 5,000 °C and in its core a temperature of a few million degrees.
  • Even though there are billions of stars, only about 6000 are visible to us.
  • Even if the sun dies today, it can send light to Earth for years to come

The sun was formed about 4.5 billion years ago. As a star of the second generation, it doesn't only burn hydrogen but also other elements, like helium and metals. They were formed when a big explosion took place, which formed our solar system.

At the sun's centre, nuclear fusion produces great amounts of energy. This energy turns into heat and light, which warms up the solar system and makes it brighter. The sun has enough energy for about 5 billion years. Then it will explode and a cloud of gas will destroy all the planets of the solar system.

The sun's diameter is about 1.4 million km. It is 10 times larger than the planet Jupiter and over 100 times larger than the Earth. About 1.3 million Earths could fit into the sun. But it is not a big star compared to others in our universe.

The sun

The sun - centre of the solar system
Image: NASA, Public domain,
via Wikimedia Commons

The core is the inner part of the sun. It is the place where the star converts hydrogen to helium. The energy travels to the outer parts of the sun as radiation. The photosphere is the surface of the sun. The chromosphere is the lower atmosphere with temperatures of up to 7000° C. The corona is the upper atmosphere. You can only see it during an eclipse. It is one of the hottest parts of the sun with temperatures as high as a million degrees C.

A solar flare happens when the sun's magnetic fields crash into each other. It causes gas to shoot out of the sun. Sometimes these flares shoot up as high as 100,000 km and can last for hours. Solar flares are not really dangerous to us but they can interfere with radio signals on earth.


Solar flare

A solar flare
Image : NASA Goddard Space Flight Center
[CC BY 2.0], via Wikimedia Commons


The eclipse of the sun is one of nature's most spectacular special effects. It happens when the earth passes through the moon's shadow. The moon always has a shadow and if the sun, the earth and the moon are in the right line, the moon's shadow passes over the earth. When this happens the sun is blocked from your view and it gets as dark as night, but only for a few minutes. This shadow might only be a few hundred kilometres wide and people from all over the world come and see it.

Solar eclipse

Solar eclipse
Image : I, Luc Viatour [CC BY-SA 3.0], via Wikimedia Commons


The sun gives us heat, light, our food and the air that we breathe. It powers the atmosphere to give us winds and rain. Even coal and oil come from plants and animals that lived millions of years ago and depended on the sun for life. The sun heats the land, the oceans and our air. Green plants use the sun's rays to turn carbon dioxide into the oxygen that we breathe.