STAR SYSTEMS / STELLAR CLASSES
Spectral classes and colonization
A star's spectral class describes its color and temperature. It also sets the environmental engineering required before an empire can found a colony in that system.
COLONIZATION RULE
Begin in the temperate band
Every empire can colonize class G yellow stars and class K orange stars immediately. The other five classes require specific technologies in the Expansion and Terraforming path. Research is checked both when a colonization order is issued and when the colony ship arrives.
Class OBlue · > 30,000 K
- Base habitability
- 15%
- Colonization
- Regional Climate Control
Class BBlue-white · 10,000–30,000 K
- Base habitability
- 25%
- Colonization
- Planetary Heat Exchange
Class AWhite · 7,500–10,000 K
- Base habitability
- 50%
- Colonization
- Ocean and Aquifer Management
Class FYellow-white · 6,000–7,500 K
- Base habitability
- 70%
- Colonization
- Closed-Cycle Habitats
Class GYellow · 5,200–6,000 K
- Base habitability
- 85%
- Colonization
- Available at game start
Class KOrange · 3,700–5,200 K
- Base habitability
- 65%
- Colonization
- Available at game start
Class MRed · 2,400–3,700 K
- Base habitability
- 40%
- Colonization
- Atmospheric Recomposition
TERRAFORMING PROGRESSION
Open new stellar environments in stages
StartG + K→
Tier 1F→
Tier 2O→
Tier 3A→
Tier 4B→
Tier 5M
The stellar-class gate determines whether a colony may be founded. Terraforming projects then improve habitability on colonies you already own, helping their population grow and allowing demanding construction to progress more readily.
RESEARCH CONNECTIONS