Question: will the sun ever blow up?

Ian Cade answered on 17 Nov 2014:

Yes

At the moment the pressure exerted by radiation being produced by fusion reactions in the core of the sun, balances the gravitational force trying to compress the sun smaller. (this is the case for the following reason: if there was ‘too much radiation’ the sun would expand and the rate of fusion would decrease… reducing the amount of radiation. If there was too little the sun would contract, speeding up the fusion reactions, thereby increasing the radiation produced).

A very summarised account of the end of the sun’s life follows (according to current understanding there are many phases/sub phases of this process):

For most of the sun’s life (including now) it ‘burns’ hydrogen. At some point there won’t be enough hydrogen in the core to fuse together and the rate of fusion will drop (the radiation being emitted will also drop) so the sun will contract until the core gets hot enough to ‘burn’ helium. When this happens there will be a sudden increase in the radiation being produced… which will push on the outer layers of the sun causing them to expand (‘explode’ to the size of the orbit of the Earth).

For our sun, this process will continue until it needs to start fusing carbon nuclei… at which point the sun will stop (it simply isn’t massive enough to compress carbon nuclei enough to cause them to fuse.)… and cool down slowly.