Well, if nothing else, after the third time I've jumped my fleet into a system and lost ~150 ships before I realized what was going on, I'm now dedicated to being more careful about checking for these things before I attack a planet.
But what is the strategy for dealing with these things? They appear in such huge clumps that each wave neutralizes a major portion of your fleet, and often you have "lost" half your forces before you can ever get to the turrets if you are running into them early game. Worse yet, in the game I am currently running they are under a force field, which seems to affect their engine damage not at all but makes it even less likely I will be able to actually take them down.
Soo... anyone have any clever strategies for these things?