Researchers at the Astrobiology Center of the National Institutes of Natural Sciences of Japan and their colleagues believe that the red absorption limit can be observed on exoplanets orbiting red dwarfs of spectral type M, at the same wavelengths as in the case of Earth.
Red dwarfs of spectral type M are small (0.5-1 solar masses) and cold (~ 3000 Kelvin) stars that are widespread in our Universe. Due to the large number of these stars, their planetary systems have recently been of great scientific interest in the search for potentially habitable planets.
One of the most important signs of life on an exoplanet is a distinctive pattern of light bouncing off the planet's surface, exhibiting the so-called "red-edge" associated with vegetation such as forests and grasslands. In the case of the Earth, a red absorption edge is observed between the red edge of the visible range and the IR range, since red light is absorbed for photosynthesis, while infrared radiation is reflected. In previous studies, predictions were made that the position of the red absorption limit on exoplanets is determined by the emission spectrum of the parent star, and on planets orbiting red dwarfs of spectral type M, the red absorption limit will be shifted towards longer waves.because potential organisms on exoplanets make extensive use of infrared radiation for photosynthesis.
In a new study, the authors show that the first oxygenic phototrophs most likely evolved underwater, adapting to the use of visible light, similar to what happened in the primary ocean on Earth. The authors studied the mechanisms of light assimilation by phototrophs using, respectively, visible and infrared radiation for photosynthesis, and showed that phototrophs using infrared radiation in their life are unable to adapt to changing light conditions at the water-land border.
Research published in Scientific Reports; lead author Kenji Takizawa.