A colony may be abandoned to allow for a free colony slot within your empire. Many players will give up planets of less than 100 fields immediately and try for a bigger planet as small planets do not have enough fields for the long-term expansion of an empire. An abandoned colony will appear as a destroyed planet in the Galaxy View. This position cannot be re-colonized immediately as an asteroid field forms when you give the planet up (The planet blows up). It may take longer than 48 hours after a colony is destroyed until the asteroid field clears and the position may again be colonized.