The aim of the WorldGen system is to generate random worlds which are diverse, interesting and also vaguely sensible. To aid in this, a broad range of planet types have been defined. This list is based on work done by John Dollan, and his far more complete version is at the ArcBuilder Site.
The original list, plus later versions, seem to have vanished from the web. There seems to be a partial copy available at https://archive.is/Okmio.
There is also a version adapted for the Eclipse Phase RPG available as PDF by James Mephit.
This version is based on a combination of these resources, plus some further modifications.
The list is split into Groups, Classes and Types. The top level groups are: