Alien Communications Hub
These medium sized structures have recently been found on the edge of human explored space and they're believed to be of alien origins as the design does not match anything in our database. A very powerful shield prevents any type of scans to be conducted on this satellite and as such all attempts to gather any intel on it have failed but after studying it's exterior design some scientists have reached the conclusion that this must be a communication satellite of sort. The structure also seems to be fitted with an array of defensive devices that make capturing it or disabling it next to impossible. So far this structure is still a mystery and it may remain so until such time that we'll make first contact with its creators.