How does the Sun burn if there is no oxygen in space?
At first glance, the Sun’s surface might resemble the flames of a roaring fire, but that’s deceptive – our local star isn’t really burning in the same way things do on Earth. Confusingly, when astronomers talk about the Sun ‘burning’, they’re actually talking about a completely different process called nuclear fusion. This involves forcing together the tiny nuclei of hydrogen (the lightest element) to create atoms of helium (the next lightest) in the high temperatures and pressures of the core. The process releases energy in a much more efficient way than the combustion we’re familiar with in a fire – and it doesn’t need oxygen.
Asnwered by Giles Sparrow