Each galaxy consists of some fixed number of solar systems (usually 400).
Each solar system contains 17 „positions“, mostly for planets but also for special functions like expeditions and trade.
When traveling within a single galaxy, the distance from a planet in one system to a planet in another system does not depend on the planets' positions, only on how far apart the systems are within their shared galaxy.1)
Each solar system reserves positions 1-15 for planets, but these are often vacant.
New players receive a Main Planet in a random system at a random vacant position 4-12.
Vacant positions (i.e. not inhabited by any player) can be permanently claimed via colonization, spawning a new planet with randomized properties.
Lower numbered positions will be hotter, as they are closer to their star, influencing resource production (namely deuterium) and the energy collected by Solar Satellites.
Planets towards either edge of a solar system (i.e. near 1 or 15) will tend to be smaller and consequently have fewer fields available for buildings.
Some universes provide bonuses to resource production (namely crystal) at specific positions.
Position 16 represents the „deep galaxy“, a frontier for discovery.
Sending a fleet to position 16 initiates an expedition.
Position 17 represents the „trading zone“ or marketplace.
Fleets travel to position 17 of their respective solar systems to place or accept marketplace trade offers.2)