Class N Planet

Class N Reducing planets range in age from 3 to 10 billion years old. Their diameters range in size from 10,000 to 15,000 km. They are usually located in the ecozone region of a star's solar system. Class N worlds are barren and rocky. Their surfaces temperatures are usually high due to an intense greenhouse effect. Water exists, but only as vapor. They have extremely dense atmospheres containing carbon dioxide and sulfides. Life forms, if any, would have to be adapted to such an extremely harsh environment. There may be single-celled organisms living in the upper layers of atmosphere. Venus was an example of such a planet.
Many worlds in the Tholian Assembly are N-class planets.

Type

Planet

Source: https://stexpanded.fandom.com/wiki/Class_N_planet