Class N - Reducing
Age: 3-10 billion years
Diameter: 10,000 - 15,000 km
Surface: High surface temperature due to greenhouse effect; water exists only as vapor
Atmosphere: Extremely dense, carbon dioxide and sulfides
Class N planets typically are found in a star's habitable zone. Similar to Earth in size, they range from 10 to 15 thousand kilometers in diameter. Due to the "greenhouse effect" caused by their dense atmospheres, they have high surface temperatures. Water on Class N planets is in vapor form, which prohibits the presence of many life forms.
The planet Venus in Earth's star system is a Class N planet.