Planetary Class
This is a system for classifying planets. It is sometimes also used for moons.
Class
Dwarf planetoids and the such like are not within this system's scope.
First Letter
The major distinction is between terrestrial and gas worlds. The first letter shows this-
R- Small terrestrial (less than 0.4 Earth masses)
T- Medium terrestrial (0.4-1.8 Earth masses)
S- Large terrestrial (1.8+ Earth masses)
F- Very small gas giant (>10 Earth masses)
P- Small gas giant (10-50 Earth masses)
B- Medium gas giant (50-150 Earth masses)
D- Large gas giant (150+ Earth masses, until brown dwarf)
Second Letter
For terrestrials (as planets and stars change, through their lives and positions, these can change. Worlds which drastically change should not be classified with these, like Mercury)-
A- Cryo worlds (Average surface temperature -270 to -200 degrees C)
B- Frozen worlds (Average temperature is -200 to -50 degrees C)
C- Icy worlds (Average temperature -50 to -20 degrees C)
D- Cold worlds (Average temperature -20 to 5 degrees C)
E- Cold garden (Average temperature 5 to 15 degrees C)
F- Garden (Average temperature 15-20 degrees C)
G- High garden (Average temperature 20-25 degrees C)
H- Tropical (Average temperature 25-35 degrees C)
I- Warm worlds (Average temperature 35-45 degrees C)
J- Sweltering worlds (Average temperature 45-125 degrees C)
K- Mild hothouse worlds (Average temperature 125-290 degrees C)
L- Hothouse worlds (Average temperature 290-360 degrees C)
M- Extreme hothouse worlds (Average temperature 360-430 degrees C)
O- Cthonian worlds (Average temperature 430+ degrees C)
Third Letter
This is useful when assessing habitability.
A- No seas or ice
B- Only ice
C- Hydrocarbon or ammonia seas
D- Lava seas
E- Less than 5% of the surface is liquid water
F- 5-20% of the surface is liquid water
G- 20-40% liquid water
H- 40-50% liquid water
I- 50-70% liquid water
J- 70-90% liquid water
K- 90%+ liquid water
