- The Death Star Mk 3 made no sense, it felt like an executive just kept saying "We need a Death Star on steroids!" It would have made more sense if its destructive power was to cause a star to explode, thus wiping out the entire system. Surely draining the power out of a sun would cause everyone to freeze to death anyway? :/
i think astrophysics should be more or less ignored here.
Even blowing up ONE planet like Alderaan would screw up the gravitational balance of a system to a degree that any class M planet would be rendered inhabitable.
I think the "draining the sun" part was also chosen for stylistic reasons. "We have until sundown to blow this thing up", as well as to have a surface battle at daytime, yet lightsaber battles at night.