Suppose you could turn off gravity... what would happen to the solar system?

Would the planets immediately smear themselves into expanding dirt/gas clouds?

Would the sun go out? Explode?

What would be the biggest thing left cohesive enough to hold itself together?

Planets and stars will indeed explode and scatter. The galaxy itself will disintegrate and scatter. All remaining forces come in pairs - positive and negative. So they cancel each other over long distances. Large asteroids and fragments of planets will survive, but that’s about it.

Shouldn’t this be in GQ?