Definition
An Asteria-class planet is a rocky body without an atmosphere, directly exposed to the radiation of its star. They are often found in close orbits and experience extreme temperatures and high meteoritic activity due to their unprotected surface.
Structure
These planets are mainly composed of silicates and contain a significant amount of metals such as iron and nickel in their crust and core. The absence of an atmosphere prevents aeolian or hydric erosion processes, preserving impact craters, faults, and solidified plains for very long periods.
Surface Conditions
Surface temperatures vary greatly between the exposed side and the unlit side. Under direct radiation, some areas reach very high temperatures, while the opposite side cools rapidly. This thermal alternation causes the progressive cracking of rocks.
Albedo and Appearance
Albedo depends on mineralogy. Some planets reflect little light due to low albedo, while others, rich in bright minerals or metallic layers, reflect more light.
Sound and Impacts
In the absence of an atmosphere, no sound can propagate. Meteoritic impacts are the main factor in surface modification, reshaping the terrain over time without attenuation by a gaseous layer.
Exploration
Exploration of these planets is hindered by extreme conditions and the lack of air. Without an atmosphere, combustion is impossible and special devices are required to regulate temperature and protect against radiation. These bodies provide direct data on the early stages of formation and evolution of stellar systems.