Atmosphere

An atmosphere was a collection of gases that surrounded a celestial body with sufficient mass, and therefore enough gravity to hold it. Examples included planets, moons, and large asteroids. Almost all species in the galaxy needed some form of atmosphere to breathe. Humans, as well as most other species, naturally breathed oxygen.

Most planets, like Cordelia Prime, had a Type I atmosphere. On worlds with a Type II atmosphere and above, oxygen-breathing species were advised to wear breath masks.

The moon Dereth had a Type II atmosphere and external breathing masks or pressurized helmets were required to breathe on the planet for more than a few hours.

The planet Zulmitune had a thick atmosphere that trapped in sunlight and heat, creating a perpetual humid and tropical climate.