This is a simple shader made using blender 2.80, with this shader you can make procedural planets. In the file you can find 4 node groups:
Planet - This node is reserved for the planet shape, using a noise map and some magic we can retrieve the result of a planet-like shape, this includes coloring based on the height, although i didn't spend much time to get it more precise interpreting the fractal types but I'm sure you can make it out.
Clouds - This node can be used to create a sorta of cloud shape
Atmosphere - This node can be used to add an atmosphere effect to a specific mesh
StarField - This one is an optional, StarField is a world node and can be used to create a fancy starfield for your render although it seems that the denoiser doesn't like much of the stars.
This shader is meant for cycles but can be used in other types of engines such as a game engine, of course baking the textures and making pbr ones out of it. Baking of the textures seems good but I've didn't test them on a game engine although this shader was meant to be used on my game that I'm currently developing.
Hope you like this one, i found it standing in the middle of my blender project files and so made me to share it somewhere. If you use it somewhere would be greatly appreciated to see your work, crediting isn't an obligation, since this shader was not made only by me but I received help and tried to improve it as much as possible.