Photosynthesis on a Planet Orbiting an M Dwarf: Enhanced Effectiveness during Flares
Photosynthesis on a Planet Orbiting an M Dwarf: Enhanced Effectiveness during Flares
复制标题
绕 M 型矮星运行的行星上的光合作用：耀斑期间的效率增强
作者：
D. Mullan;H. Bais
在M矮星附近的行星上，氧光合作用（PS）的有效性取决于波长在400到700纳米之间的可见光子的供应。在本文中，我们量化了与M矮星相关的两种情况下PS的有效性。首先，利用静止（非耀斑）状态下的M矮星的光子，我们发现在其母恒星的宜居带（HZ）的M矮行星上，对于具有中M光谱型的耀斑恒星，PS的有效性比地球上低10倍。对于具有晚m光谱型的耀斑恒星，PS效率（PSE）比地球上的要小100倍或更多。其次，利用在耀斑期间入射到HZ行星上的光子，我们发现PSE可以比静止值增加5-20倍。对于中m光谱型的耀斑恒星，我们发现耀斑期间的PSE值可以增加到地球上的50%-60%。然而，对于m晚期的耀斑恒星，即使在耀斑期间，PSE仍然比地球小一个数量级。我们建议，对于M矮行星上的生物过程，恒星活动周期可能取代轨道周期作为“年”。
On planets near M dwarfs, oxygenic photosynthesis (PS) will occur with an effectiveness that depends on the supply of visible photons with wavelengths between 400 and 700 nm. In this paper, we quantify the effectiveness of PS in two contexts that are relevant for M dwarfs. First, using photons from an M dwarf in its quiescent (nonflaring) state, we find that PS on an M dwarf planet in the habitable zone (HZ) of its parent star is less effective than on Earth by a factor of 10 for a flare star with mid-M spectral type. For a flare star with late-M spectral type, PS effectiveness (PSE) is smaller than on Earth by a factor of 100 or more. Second, using photons that are incident on the HZ planet during flares, we find that PSE can increase by factors of 5–20 above the quiescent values. In the case of a flare star with mid-M spectral type, we find that the PSE during a flare can increase up to as much as 50%–60% of the values on Earth. However, for a late-M flare star, even during flares, the PSE remains almost one order of magnitude smaller than on Earth. We suggest that for biological processes on M dwarf planets, the stellar activity cycle may replace the orbital period as the “year.”