Buying solar systems | Space stage Spore Guide
Last update: 11 May 2016
If you are keeping good relationship with selected civilisation - you can start trading with them. It is the first step to buying the whole solar system where selected planet belongs to.
When the trade route is set - you would just have to wait till the selected civilisation would allow you to buy their planet. It works exactly the same way as buying the cities in the civilisation stage.