I wanted to make a Solar system in Blender. Everything on the scene is made pitch black (including World), except planets and Sun. I want that planets cast shadows so I added an Emission node to the Sun, but planets are still fully visible. All planets just have Image Texture nodes like this. And this is Node Tree of the Sun. My render engine is Cycles.
You need to disable Ambient Occlusion in the world properties.
If you use the shader of the sun itself to light the scene, your texture will be overwhelmed by the emission part and any detail will be lost.
You can emulate the light from the sun by using a point light centered on the sun itself. Remember to set its size to a high enough number so that it is bigger than the sun object or else light won't get through to your planets. You can then set the emission strength of the sun to a low enough value that it still appears to be glowing but you still see all the details of your texture.
Details on the point light (Adjust these settings depending on your scene) :