Celestial Agent Beacon Site

This is an entry in the Type column of the Overview Panel.
Its icon in the IC column is the beacon designation (an upside down triangle with a tail on top), colored yellow.
To make these appear in your Overview Panel, go to the Overview settings-->Filters tab-->Types subtab-->Celestial section. Place an X in the checkbox entitled Beacon. These sites contain celestial agents. The agents can be for epic arcs, cosmos, etc. They are not combat sites per se, but a few do have NPC pirates that can aggress.