Class U planets represent the upper limits of planetary masses. Most exist within a star system's Cold Zone and are very similar to Class S and J planets. However, Class U planets occasionally form within a star system's Hot Zone. If they are sufficiently massive (13 times more massive than Jupiter), deuterium ignites nuclear fusion within the core, and the planet becomes a red dwarf star, creating a binary star system.
- Extreme attrition damage to units outside Pressure Domed facilities.
- Due to nature of surface, ground combat on surface is impossible (100% attrition to units forced to land on planet)
- No Water for Naval Units
- No Water for Fishery or Waterport
- Extreme Atmosphere, Air Units only 25% effective.
- Facilities can not function here unless they have the Repulsorlift Upgrade, immediately destroyed on surface.
- Facilities can not function here unless they have the Pressure Dome Upgrade, or suffer damage.
- Facilities can not be constructed here, they must be transported here.
- Mines do no produce anything.
- Gas Mine produce x2 Energy.
- Extreme Weather Events.
- Risk of becoming a Star.