Question: Why does the sun explode?

Lydia Bach answered on 21 Nov 2014:

Heya,

Do you mean when it becomes a red giant in about 5 billion years?
At the moment the sun is stable because the energy released outwards from nuclear fusion of hydrogen going on in its core balances gravity that pulls the mass inwards.

in about 5 billion years or so the sun will have burned its hydrogen stocks and start to contract because there won’t be enough energy released in the core. That contraction will heat up the core and the outer layers of the sun, where hydrogen is still not depleted and will continue to burn and to expand.

As the outer layers expand, the radius of the sun will increase and it will become a red giant – at this stage it will engulf earth.

Around the same time the core will become so hot from the gravitational pressure that helium begins to fuse into carbon. – Once the helium is burned up the core finally cools…