CLASS D
Class D worlds are the most common planetary bodies and exist in almost every stellar system. They are all relatively small, airless moons and asteroids that are essentially barren balls of rock. Earth's moon, Luna, is a typical example of such worlds.
Almost all fo these worlds are lifeless, although a few are home to vacuum-dwelling life or life-forms that live in subsurface cavern complexes. While typically useless for any purpose except mining, some of the larger Class D worlds, like the Andorian world of Weytahn, can be terraformed.
AVERAGE GRAVITY
Negligible to 1G; most are between 0.05 and 0.5 G.DANGERS
Deadly atmosphere (vacuum), hazardous, hostile, or deadly temperatures; hazardous or hostile radiationCLASS H
These are hot, dry terrestrial planets, which have little surface water or ice and are, at best, marginally habitable by humanoids. Although some Class H worlds have oxygen-argon atmospheres, many have atmospheres that are mildly poisonous, making long-term survival impossible. Humanoid colonies have been established on Class H worlds, but they rarely thrive.
AVERAGE GRAVITY
0.5 to 1.5 Gs.DANGERS
Hazardous or hostile temperatures, possibly hazardous atmospheres.CLASS J
Class J worlds are the most common gas giant planets found. These are large worlds that are typically between 3 and 15 times Earth's diameter that have enormous and dense atmospheres primarily composed of either methane ( on smaller Class J planets) or hydrogen (on larger Class J planets), and their surface is almost impossible to reach due to the size and density of their atmospheres.
No Class J planet is habitable by humanoids, and they are impossible to terraform. However, some have their own entirely airborne alien ecosystems and may even be home to exceptionally alien and intelligent creatures.
Class J planets can be found anywhere in a star system, from intensely hot worlds close to their primary star to distant frozen worlds. Some Class M planets orbit Class J worlds as moons.
AVERAGE GRAVITY
0.8 to 3 Gs.DANGERS
Deadly atmosphere; hostile or deadly temparatures; possibly hazardous, hostile, or deadly radiation.CLASS K