"Habitable" can have two separate meanings, and both meanings can be true at the same time.
Habitable Orbit Zone
Worlds in the habitable orbit zone are commonly referred to as "habitable worlds". This does not however mean that those worlds always support life. Worlds in the habitable orbit zone are just much more likely to support life than worlds in other orbit zones. In addition, worlds in the habitable orbit zone are the only ones that can naturally support sentient life.
For more information, see the Orbit_Zone page.
The environment of a world can be habitable, which means it naturally supports plant and animal life without additional life support.
Note: This can be the case even when the world isn't in the habitable orbit zone.
An environment is habitable if all these conditions are true:
- The world is in the inner, habitable, or outer orbit zone
- The world's atmosphere density is between 15 and 85 percent
- The world's atmosphere type is standard or tainted
The system map will show the world's atmosphere as "Breathable" if the environment is habitable. If it isn't, it'll be listed as "Toxic".
For more information, see the Atmosphere page.
If a world is both in the habitable orbit zone and has a habitable environment, it will be able to naturally support sentient life, which will mean it can have an indigenous population and be able to spawn one officer. This is in addition to standard wildlife.
Semi-habitable worlds are sometimes referred to as frontier worlds.
Worlds in the inferno or frigid orbit zones cannot support life in any way. Some uninhabitable environments can however support plant life.
Buildings on these harsh worlds will require life support and armor. Alternatively, buildings without necessary life support can be built in a biodome.
For more information, see the Harsh_Environment_City page.