Why Red Dwarfs Have Fewer Chances for Photosynthesis ⚡ экспресс
A thermodynamic model has been developed to determine the maximum useful work of stellar radiation for photosynthesis. For Earth-like planets in the habitable zone, the reserves of photons capable of driving water oxidation are about five times greater for solar-type stars (FGK) than for red dwarfs with temperatures around 3000 K. The reason is that cold stars emit less short-wavelength radiation and fewer photons with energy above the water-splitting threshold. Moreover, the exergy fraction (energy available for work) in their spectrum is lower, which imposes strict limits on oxygenic photosynthesis. It’s like trying to power a complex mechanism with a dim light bulb — there’s plenty of energy, but most of it just heats things up rather than doing chemical work.
Oxygenic photosynthesis requires splitting water. It's kind of like a water wheel: to make it spin, you need a strong current. Light acts as the current, and light particles are the streams. For red dwarfs, the most common stars, the light is "cool" and weak — the streams barely move the wheel.
But even on Earth, with its bright Sun, the wheel uses only a drop of the available energy. The theoretical maximum oxygen output is thousands of times higher than what's actually produced. So complex life might be hiding unnoticed — and we should search for it around stars similar to ours.
🎯 The upper theoretical limit for oxygen production on Earth is thousands of times higher than what plants actually produce.