INSIDE STARS

Over millions of years since the Big Bang, stars have created all the chemical elements in the Universe.

But after the Big Bang, only simple elements like hydrogen and helium floated about in the Universe. So where did other elements like carbon and oxygen come from?

Apart from the hydrogen and helium that originated in the Big Bang, everything else in the Universe has been manufactured inside stars by a process called 'nucleosynthesis'.

Star factories

After they are born, stars become huge nuclear processing plants. Unlike nuclear plants on Earth, stars don't produce energy by splitting the atom - known as 'nuclear fission'. They join atoms together in 'nuclear fusion'.

Find out how stars are born

Currently, scientists are hoping to harness this power source to generate energy on Earth. They're trying to generate the massive temperatures of around 100 millionºC required to kick start this process.

Step-by-step chemistry

Newly born stars begin by fusing their lightest atom, hydrogen. In the core of the star, these hydrogen atoms fuse to form the next heaviest element, helium.

Then when the hydrogen runs out, the helium atoms fuse together to form carbon. Then when the helium runs out, the carbon atoms fuse to form oxygen.

This manufacture of heavier and heavier elements continues until the star finally dies. The Sun will halt during the carbon-oxygen stage of fusion.

Stars a few times bigger than the Sun will eventually have cores made entirely of iron. This is as far as nuclear fusion reactions can go inside stars. All the elements heavier than iron are created in huge supernova explosions. These are the death throes of massive stars.

Discover what happens when stars die