An electronic device that projects an ever-widening conical wave of energy that, at full capacity, will surround an entire planet, protecting it from hostile invaders. In many cases, the shield itself is a sphere of electromagnetic energy, though in other instances, a physical structure may also be required. These sort of planetary defense systems are similar in function to Dyson spheres. The planet Euphorix in the Vega star system had such a planetary shield, and it is the only thing that kept them safe from the conquering Citadel empire.
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