Unlike Jedi and sith, there doesn't seem to be any morality difference between photon and graviton based powers. Any solarion can attune with either force from round to round and there doesn't seem to be any issue with a good solarion using gravity or a evil solarion using energy.
Actually it seems NONE of the new classes have any alignment restrictions whatsoever. Wonder why that is? ;)
Because Alignment apparently doesn't mean anything in Starfinder. I'm actually kinda curious why they even bothered keeping it.