The sun isn't big enough to go nova, period. It will swell up in ~5 billion years when it runs out of hydrogen in the core and starts burning helium. Then the sun will start climbing the fusion chain up to iron and there the fusion reaction in the core will die out. When this occurs the outer shell will kind of just slough away leaving a planetary nebula and an extremely hot naked mostly iron core. This core is a white dwarf and will just continue to glow for a few tens of billions of years until it loses all its heat. No fusion is happening in this bad boy it just glows from the residual heat and the heat is so hot it takes longer than the current age of the universe for that heat to dissipate.

Back to the original point though is that the sun won't explode in a supernova because it lacks the mass to do that. You need a star that is at least 8 times as massive as the sun in order to get a supernova.