Of course your laws of physics work well enough when applied to the situation they were designed to describe. They didn't start out that way, as the flat earth
theories that held sway in the past clearly demonstrate. People were assumed to have developed disease due to demons casting spells, and the demonstrated
relationship between passing germs from the dirty hands of a physician from one patient to another was resisted by the establishment just as dropping the flat earth
theory was resisted. Comfortable theories are clung to, for no other reason than change, being open to change, requires a momentary discomfort. The theories you
smugly pronounce are correct were not the theories you smuggly pronounced as correct yesterday, but that doesn't stop you from making such pronouncements.
Your theory about brown dwarfs exists based on those dwarfs you have observed, wherein they had to be large in order to be observed. Is it not possible for there to be something out there that you have not observed? A composition of a planet not quite in the mix you find in your Solar System, as you know it to be? You operate a slow burn in your nuclear power plants, which otherwise would be the fast burn of a nuclear explosion that occurs when no braking mechanism is in place. Is it entirely impossible for suns to have mixed composition? For a slow burn to be in place? For a planet to have some of the composition of a sun as well as a composition of a solid planet? This is simply not possible, and because you have not observed it, then it does not exist?
Please spare us your current theories about what makes sun's burn, as you have no more proof of that than you do what the composition of the core of your very own planet or a proper description of the workings of the atoms you yourself are composed of. Your current theories are a work in process, and if you are honest you will admit that.