Life on other planets might reveal itself through its waste. Biosignatures could give away the existence of plant-like beings on other worlds. But how would photosynthesis work under different stars? Chitnavis and colleagues model how different stars could shape this process. Their findings suggest that while Sun-like stars might support familiar plant structures, cooler stars could demand exotic adaptations.
Star type profoundly influences potential photosynthetic strategies. G and K stars, like our Sun, could support diverse plant life with small, modular light-harvesting systems. In contrast, cooler M-dwarf stars require large, specialised “funnel” structures to efficiently capture limited photosynthetically active radiation. For the coolest M-dwarfs, even these adaptations yield lower efficiency. These findings refine our understanding of possible alien plant adaptations and inform the search for potentially life-bearing exoplanets.
The researchers developed a mathematical model of photosynthetic systems, simulating light-harvesting under various star types. They analysed optimal antenna structures for capturing light, considering factors like pigment arrangement, energy transfer, and thermodynamic constraints. The model explored star temperatures from 2300K to 5800K, representing cool M-dwarfs to Sun-like stars. By varying antenna size and absorption peaks, they determined the most efficient configurations for each stellar environment.
This study builds on recent experiments showing some organisms can grow under simulated M-dwarf light. It provides a theoretical framework explaining why certain life forms might thrive or struggle in these conditions. By applying fundamental thermodynamic principles to light-harvesting, the research establishes concrete limits on feasible photosynthetic processes across different stellar environments.
That the irradiant flux from a G-star can support abundant oxygenic photosynthesis is not surprising, given that we already have a real example of this on Earth. The fact this is likely also true for the smaller, cooler, and very orange, K-type stars is more interesting and broadens our search criteria beyond Earth-like planets orbiting Sun-like stars.
Chitnavis, S., Gray, C., Rousouli, I., Gillen, E., Mullineaux, C. W., Haworth, T. J., & Duffy, C. D. P. (2024). Optimizing photosynthetic light‑harvesting under stars: simple and general antenna models. Photosynthesis Research. https://doi.org/10.1007/s11120-024-01118-1 (OA)
