The planet with their giant super important simulation was being eaten by it (and might still be eating it, we only decoupled it from the sun)
I'm kind of surprised they haven't telaported onto it and tried shutting it down or converting it into something to nullify the sun like in the future that they attempted to make, and you gotta admit it'd make an interesting strike :p
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They really didn't have to, they figured we would or one of their biggest threats can be taken care of without doing anything. It's a win-win for them, plus their main concern for them was their forces in Nessus especially with the arrival of Calus.