ok I have a space ship that was built using an asteroid so part of its bulk is the original rock but with a nose and engines etc sticking out of it. It's dead, reasons don't matter but it's been floating out near Neptune. Would it freeze? Would that create ice either on the rock areas or the metal? Any help gratefully received!
Pretty sure it would be at a temperature below the freezing point of water. But no ice crystals on the outside. you need water to form ice crystals - where would it come from? ice sublimates in a vacuum. Without a gravitational field at least equivalent in strength to a moon, it's going to sublimate off into space, never to return. Now, inside the space ship, if there are sealed (or relatively sealed) areas, there can be ice.
Wait! Neptune? I've will not sublimate that far out, in astrophysics there is an term for the line in space around a star where ice can form: the frost line. Inside of that line, ice sublimates because the energy from the sun provides enough energy to overcome the electromagnetic attraction water molecules have to each other. Beyond that line though, the temperature is low enough that the electromagnetic attraction between water molecules actually overcomes the heat energy between them. Remember that matter does wonky things in extreme energies. Out by Neptune you'd probably be somewhere around 50 kelvin. That line is just inside of Jupiter.
Sometimes my jaw drops down, looking at the lengths authors consider to be necessary for their work. I understand it from “make your setting shine” perspective, but find it hard to assume, that majority of readers will have grasp over astrophysics. “Stars Wars” with its Death Star is an interesting concept, yet a complete failure from logic’s standpoint. Do you have a specific auditory?
When I see reviews praising a scifi novel for getting the science right, I'm more likely to buy it even though I know I'll have zero idea what the science is about. As long as the author can make the actual science interesting to read, it's worth my wallet.