Nuclear fusion is generally presented as the sci-fi energy source of the future, providing unlimited, clean energy, but, while listening to the audiobook version Atomic Adventures by James Mahaffey, I was reminded that the astronomical output of the sun comes from its astronomical mass:
At the center of the Sun, fusion power is estimated by models to be about 276.5 watts/m3. Despite its intense temperature, the peak power generating density of the core overall is similar to an active compost heap, and is lower than the power density produced by the metabolism of an adult human. The Sun is much hotter than a compost heap due to the Sun’s enormous volume and limited thermal conductivity.