Don't even start with science stuff when it comes to Star Wars. Absolutely EVERYTHING is wrong in these movies in that regard, so it's no use talking about it.

Anyway, because I'm in the mood, I'll answer your question. I didn't see the movie and don't know how exactly that blocking should take place. But in any case, you won't kill a solar system with that. Not even a single planet. Imagine the sund would be blocked, earth would be fine for several years. By "fine" I mean that a lot of the population would die, but anyway. Earth wouldn't be TOTALLY fucked. The planet produces heat itself, which is enough for life in certain regions. On top of that, you can't block gamma rays, so the earth would still get energy in some form. But even if the sun simply disappeared, earth wouldn't go down instantly. The heat would go down with time without a sun, but we're talking about centuries at this point at the very least. So the question is, do they block the sun for good? Or just for a limited time? Say they are blocking the sun for a whole year. The planet would get dark as fuck, sure, but other than that, not too much would happen. If they block the sun for good, yeah, the planet is fucked - in about 10,000 years. 

Blowing up a planet is it's own beast. There's no turning back if you do something like that, that's it. Aaaaaaanyway, it's as good as impossible. To literally blow up a planet like earth with a weapon that turns mass perfectly fine into energy (a nuclear reactor has an efficiency of about 1 %, so yeah...) you would need the masses of 10 jupiters - at the very least. It just ain't happening. It would be better to just change the course of a big ass asteroids, of which are plenty in pretty much every solar system, using a gravity tractor.

edit: Oh, and screw both solar power and windmills. Way too inefficient. Nuclear power is the way to go, it's best for humans and nature. We should use our reactors from today until we got nuclear fusion figured out, if you ask me. 

I watch VSauce all the time.
 And I work at plant Vogtle (soon to be the biggest nuclear power plant in America). I was just being cheeky.

That was such a good counterargument, by God you should be a politician. You can't just say "No he's a Sith because I say so" when being a Sith requires a very specific set of circumstances in the Canon. But keep believing what you want, because you will no matter what reasoning others use. Good day.

Yeah, that was my one big disappointment as well. I kind of feel like John Williams was phoning it in on this soundtrack. It wasn't bad by any means, but none of the new tracks were particularly catchy or memorable.

Call me crazy but.... wouldn't blacking out an entire sun be worse than blowing up some planets. They killed a solar system every time they charged it!!

And the explosion wasn't that big. Just goes to show, solar power isn't the way to go. Power that bad boy with windmills!

Yes, I agree. But does he leaves just because Kylo falls? Movie strongly suggest Kylo did something terrible to Luke's foundation, which can be seen in Rey's flashback of Kylo standing (with what seems to be another group of people) next to a lot of bodies; which again means Kylo is no pushover when it comes to getting his hands into a fight.