Class C: Small Rocky Planetoid - Similar to Gothos

Class N: Extremely high surface temperature, and an atmosphere inhospitable to most life.

Class H: Uninhabitable desert world. Tau Cygna V is one such planet.

Class K: Planet that is barren and has no native life, but could be hospitable with terraforming or if buildings were constructed inside habitable domes. Mars is considered a Class K world.

Class S: Largest designation for gas giant. Ultra giant, not suitable for Iffens.