Ethan Siegel wrote a fascinating piece on Medium that uses our existing understanding of physics to extrapolate what the far (and I mean far) future of our solar system might look like:
“But neither the accelerated expansion of the Universe nor our impending great galactic smashup will, in all likelihood, affect our Solar System. (In fact, you know how many stars are likely to undergo a collision with another star due to the entire merger process between our local group’s two largest galaxies? Just six, out of around a trillion stars!) Instead, let’s focus on our little corner of space in the Solar System, and look at exactly when certain spectacular events are likely to occur!”
It's a slightly different perspective of the future than the one portrayed in one of my favorite book series, but I'll let it go this time.