Habitable zone
Habitable Class (hClass) — Classifies habitable planets based on temperature: very cold (< −50 °C);  cold; mesoplanets (M) = medium-temperature (0–50 °C); thermoplanets = hot; very hot (> 100 °C). Mesoplanets would be ideal for complex life, whereas class hP or hT would only support extremophilic life. Non-habitable planets are simply given the class NH.