Lifesize Planet Shading, Is It Possible?

Let me preface this by saying I’m new to game engines, so sorry if this question sounds dumb. Despite my efforts, I cannot seem to find an answer.

I’m setting up a scene for an environment, and would like to have a planet (and some moons) as a prop in the background. I’m starting by trying to do one to scale, since that seems like the most straightforward approach to make it look correct. Everything looks fine before I build lighting, but after not so much (see photos). The sphere sits at about 3k polys so nothing really crazy there. It’s size is 140,000 km (140,000,000,000 unreal units), and sits about 140 billion unreal units from the camera. I have a light mass importance volume set up that is the size of the landscape (100m x 100m x ~20m) centered at the menquinn. So, is it possible?