It won't be accurate.. Planet composition will not be accurate. Geophysics says that with acceptable gravity turns planets into formidable stellar bodies ( if that's the right word). Earth for example would be nigh indestructible in the physical sense. Everything on the surface would die in a catastrophe. But in real life what can you think of that would effectively destroy earth? Excluding out of system things. Supernova. Gamma ray pulses, etc. the core is a spinning magnetic crystal of molten iron. A nuclear weapon wouldn't do anything to that.. But again I'm distracted.. Sentinels are sentinels.. And this isn't really a fight of how but of how many. Sentinels are the very literal word of exponential. Every one of their strengths increase exponentially.. It would be a matter of how much your Death Star could take. And this is one thing out of the halo universe.