When I approach planets, moons, asteroids, and comets, they all appear WAY too bright. They're so bright, that they're just white until you get close to the surface. Even Earth looks like this. When I try to render brightness, it makes everything else go dark, and the planet is still slightly too bright.
If you're using 0.9.7.2, the game will default to an expose setting of "Normal." Go into the Graphics Settings, and either the "None" or "Simple" settings will yields planets' true brightness.
I too thought this was a bug when I encountered it. Luckily, this was changed in 0.9.7.3 and later.