PLANET
CLASS N: NEPTUNIAN
TYPE
Ice giant
CORE
Iron, silicate rock, ices
MANTLE
Water, ammonia, methane ices
ATMOSPHERE
Hydrogen, helium, ices
LIFE
None
Class N planets are large, cold worlds that linger on the outermost edges of a star system. Though they tend to look similar to the more traditional gas giants, they are structurally very different. While a gas giant might be composed of 90% hydrogen and helium, an ice giant is only about 20% hydrogen and helium, with the remainder of that mass in the form of frozen volatiles such as water, ammonia, and methane.
CLASS N1: BANDED
Though very cold, these worlds tend to produce enough internal heat to support violent storms, which take shape in banded layers of clouds in the upper atmosphere. Winds may approach 2,200 kph in the most violent storms.
CLASS N2: CLOUDLESS
Cloudless worlds tend to receive very little warmth from the sun. Additionally, they generate very little heat from within... while large storms are not uncommon on these worlds, there is simply not enough internal heat for visible convection boundaries to develop.
SUBCLASS ND: DWARF
Not all ice giants are... giant. Smaller than average planets are deemed dwarfs.
SUBCLASS NM: MOON
In very rare instances, a Neptunian world can form as a moon around another much larger planet... probably a giant.
SUBCLASS NR: ROGUE
A planet that has been ejected from its star system and is adrift in interstellar space.
SUBCLASS NS: SUPER GIANT
A planet that is significantly larger than average. They tend to stay in the outermost regions of a star system and act as a "shield" to the inner planets, as their powerful gravitational fields tend to divert comets and asteroids away from the interior of a star system.
SUBCLASS NX: IRRADIATED
A planet that is heavily irradiated by its parent star.