/sci/ - Science & Math

I have a question for you space-loving roamers of /sci/. If we were to store a globe of pure water in space, how large could it get before bad things happened at the center from pressure? We could give it an atmosphere to hold in the water from boiling away, and let's say there are orbital magnetic field generators to protect the atmosphere, so we don't have a solid core. This could prove to be an actual human accomplishment, in some distant future, so let's theoretically beat them to it.