This is a Core Guard Post and will only spawn on AI Homeworlds.
It must be destroyed before humans can damage the AI Command Station on this planet. If this is an AI Homeworld, all Core Shield Generators (if enabled) in the galaxy must be destroyed before this can be damaged.
It increases AI Progress by 1 when destroyed and, unless the Lazy AI option is enabled, also increases the AIP Floor by 10.
Also, this one is a Brutal Guard Post. They are considered much stronger and AI Homeworlds can only have a few of them. (The Brutal AI Type can also have one on each MkIV planet.)