Man.. that second shot is... well.. to put it bluntly, the lighting sucks man... Its tooo bright.
I would expect some blue light from the vortex, and maybe some very dim green light from the nebula. Unless of course you have a sun on the other side of the thing. Even then, the light is a bit harsh. Try using shadow maps. I pretty much swear by these things now. Unless you're doing a scene that would call for really harsh lighting, like a laboratory or something, I would use shadow maps.
The lighting in the first one is pretty good though. Shadows are a bit sharp, but thats just my preference.