Just a physics/astronomy question from a simpleton. But a curious simpleton nonetheless.
The general rule of thumb seems to be that larger objects, on an astronomical scale, will have less and less mass/density. AFAIK it is our own puny little planet which is the largest rock solid object we know of. The big planets in our solar system are all gas giants, and the even larger ones we've found in other solar systems always have less mass than Jupiter.
Is there some kind of threshold where rocky/solid objects just can't get bigger? I am excluding black holes since at that point they just don't give a shit and live by their own rules.