I am interested in a character or race of humanoids similar to the green man in the tent in Wolfe's Book of the New Sun.
What qualities would the Sun need to have in order to support a race of human-like beings that rely mostly on photosynthesis for energy? Let's say they eat some sugar, some minerals, but subsist mostly on water and sunlight. They still move around (although could do so at a much slower pace if need be), manipulate things with their hands, and communicate with others in some way. Maybe they're slightly smaller than a modern human...call a 5'6" man tall for the species.
For our sun specifically, is there a stage in its life such that it would output enough energy for this to be possible? I remember a little bit of photosynthesis from school...plants get NADH from it or something. Is there a plausible way for photosynthesis to generate ATP? What would this sun mean for the environment and mammalian forms of life?
I guess this is a question about both the sun and photosynthesis.