This was one of the first posts that made me sign up for Reddit some 10+ years ago. Now I've been on Lemmy for a week and I see it again for the first time since.
It actually won't explode, just implode. The process of becoming a red giant is quite gradual even by cosmological standards, taking about a billion years.
I'd always kind of assumed the sun would hit some point of not having enough fuel to sustain the fusion reactions and everything going to hell pretty quickly, but I suppose it does make sense that it's a slow process.
The sun will never explode. In a few billion years it will puff up to a red giant with a circumference somewhere around the orbit of earth or mars when it starts burning helium. After the helium runs out it will lose the outer layers and become a stellar remnant called a white dwarf. It’ll stay that way til it fades to darkness in a few hundred billion years. At no point will it explode as it doesn’t have enough mass to explode.