Protection
From Planetarion Wiki
When a planet is first created, it is protected for 24 ticks after it signed up. During protection the planet name will show on the galaxy screen with square brackets around it, signifying that it cannot be attacked. It is not possible to launch fleets (not even defence fleets), perform covert operations or donating to the galaxy fund while under protection. Similarly, planets under protection cannot be attacked by ships or covert operations and for all intents and purposes are safe from outside interference.
Prior to Round 34, protection lasted for 72 ticks.