Ask a grown-up: what will happen to the planets when the sun blows up?
Dr Lucie Green, doctor of solar physics and Royal Society University Research Fellow at UCL's Mullard space science laboratory, replies: As the sun starts to run out of fuel, the first thing that will happen is that it will swell up and become extremely large. It will also look redder in colour and become a type of star that we call a red giant. The nearest planets will be swallowed by the sun. This includes Mercury and Venus and probably Earth, too.
Then the sun will blow off its outer layers so only the material at the very centre remains. What's left will shrink and become a type of star we call a white dwarf.
The change in the sun's mass will affect the planets held in its orbit. The pull of gravity that the planets feel depends on how much mass the sun has. When the sun sheds its outer layers, the planets will start to move further out into the solar system.
The sun is about halfway through its life now though – so, don't worry, all of this is a long way off.
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