Why is the sun hot?

The Sun is the star at the centre of our solar system. It’s millions of miles away but we can feel some of its warmth here on Earth. My 6-year-old wonders: why is the Sun so hot?


The Sun is mostly made up of hydrogen and helium. It also contains small amounts of oxygen, carbon, neon and iron.

Inside the Sun, a chemical reaction is happening: hydrogen atoms are squashed together until they turn into helium atoms. Scientists call this process ‘nuclear fusion‘ and it produces lots of energy, which is released as light and heat.

Inside the Sun, millions and millions of hydrogen atoms are fused together every second, releasing an enormous amount of heat energy. This makes the Sun really, really, really hot and very bright and explains why we can feel some of that heat and see its light from 93 million miles away, here on Earth!

Why not check out this webpage for more information about the temperature of the Sun, or have a listen to this song about why it is so hot? And, if you like, you can find out more about what kind of star our Sun is in my answer to why are stars white?.


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