This is not good news for the Earth. Closer planets like Mercury will be completely engulfed by the swelling Sun. Earth will be entirely vaporised and all life on our planet will end. But there's no reason for alarm – we have a few billion years to plan our escape!
 Find out about the future of space exploration
Over the following billion years, the Sun will gradually die. As a star's core crashes inwards, it eventually becomes hot enough to ignite another of its constituent atoms, helium.
Helium atoms fuse together to form carbon. When the helium supply runs out, the centre collapses again and the atmosphere inflates.
The Sun isn't massive enough to fully re-ignite its core for a third time. So it goes on expanding, shedding its atmosphere in a series of bursts.
White dwarf
The dying core eventually forms a white dwarf – a spherical diamond the size of the Earth, made of carbon and oxygen. From this point on the Sun will gradually fade away, becoming dimmer and dimmer until its light is finally snuffed out.
Supernovae explosions
When a star a few times larger than the Sun runs out of fuel, its end is far more spectacular. A massive shock wave radiates throughout the whole star, which heats up to around 1 billion°C.
Then it explodes as a supernova. This flash is as bright as a whole galaxy and leaves behind a rapidly spinning neutron star.
Read our guide to star types
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