NPCs can never take the captain role.
The captain role requires either a specified captain's berth on a spacecraft, or other types of berths which can also be reserved for the captain. A spacecraft must always have this berth, so berths are reserved as needed.
Captains have full command authority over a spacecraft. They are able to view, modify and delete the current mission, along with having full authority over all troops, crew, passengers and officers on the ship's roster through the Unit Orders (
Wormholes track who first explores them. The name given once a spacecraft travels through an unexplored wormhole is the name of the ship's current captain. Also, the avatar's "Wormholes Explored" count in the Bio (
F8) UI will be added to.
In addition, a number will be appended to the wormhole's name, that being which number of wormhole it was in the avatar's explored count.
If the ship is missing a captain, but contains NPC crew that are still commanded to travel through a wormhole through chain-of-command authority, the wormhole explorer will be listed as "Unknown". This also won't increase the avatar's exploration count.