NanoFX atmospheres are suns placed inside the planet, so this could be result due to an error.
I have the same idea. I played another game and warped to SB12, noticed the sun wasn't there. I looked around and realized it was back inside the planet like it was supposed to be. Then I docked and the planet core was back to where it is in the screen shot. Obviously docking has something to do with it.
Thanks for the reply's guys. The error isn't something critical just curious as to what it was.