An interesting thing about Dyson spheres and red dwarf stars, is that the surface temperature of some red dwarfs is less than the melting temperature of some re

An interesting thing about Dyson spheres and red dwarf stars, is that the surface temperature of some red dwarfs is less than the melting temperature of some refractory materials, like tungsten or diamond. In principle, one could build a Dyson sphere directly on the surface of such a star, and use buoyancy or the gas pressure of the star to keep the Dyson Sphere material 'afloat' on the star. Note that the surface gravity of even a dwarf star is very much higher than on a planet; however this is actually helpful if using a buoyant construction. It's too bad that most red dwarf stars are so low in carbon that extracting the carbon from the star itself to build the sphere may not be feasible. If it were feasible, it would answer the common Dyson Sphere engineering question of "where do you get the mass to build it?". Another interesting thing is that if you build a Dyson sphere with the intention of using it as a heat engine between the star's surface temperature and the cold of deep space, the Carnot efficiency is so high that the Dyson Sphere's blackbody emission temperature is significantly lower than the star's normal surface temperature. As long as you have an energy sink (such as performing nuclear or chemical reactions that store energy, and leaving it stored), the outer surface of the Dyson Sphere could be a relatively comfortable temperature.