Human-space forms a rough sphere centred on Sol, with a radius of 250 parsecs. (See the Atlas.) Within this volume are some 40 million stars. About 50% have planetary systems and 10% of systems have one or more worlds suitable for hydrocarbon life. Therefore there are an estimated two million systems capable of sustaining some sort of life within human-space. Most of these are however unsuitable or uncomfortable for humans; only about 3% (around 65,000 worlds) can sustain humans. Human-space represents only some ten-thousandth of the volume of the Galaxy.
Humans have colonised approximately 560 worlds, mostly within 100 parsecs of Earth. Some human worlds are much further away, as colonists expanded into regions unoccupied by other sentient species. The remainder of human-space consists of human populations on worlds originally colonised or inhabited by other species.
