I had this strange situation happen in my current game:
I colonised a planet that was not optimal for my race
I forgot to start terraforming it
I built the government building, then other buildings and a starbase
The population remained tiny - just a few thousand
An enemy attacked the planet. Most of the attacking ships bombed/fired on the planet first and not my ships
I destroyed all of the attacking ships after a few rounds, but all of my population was killed off
The next turn the sitrep reports the colony has been destroyed.
I send a colony ship and resettle the planet: THE STARBASE WAS STILL IN ORBIT
If another civ had colonised the planet, would they have got my starbase
I wonder if I killed off the population on an enemy planet but left the starbase/shipyard/stargate in place and let the turns go to 50 if I could use this to my advantage?