Astrobiology Center (ABC), National Institutes of Natural Sciences (NINS)
National Astronomical Observatory of Japan (NAOJ) | 2017 Sep 12
New prediction of a detection wavelength for searching phototrophs on exoplanetsM-dwarfs or red dwarfs are small (0.5-0.1 solar-masses) and cool ( ~3000 Kelvin) stars, and are abundant in universe. The Sun-like stars have been attracting most attention as a plausible target for searching habitable exoplanets. However, nearby M-dwarfs are becoming the most extensive targets for habitable planet searches because they are the most abundant nearby stars and thus could be the first candidate for detecting any biosignatures on exoplanets via transit or direct imaging observations in near future.
- Artists impressions of a habitable planet around M-dwarfs (left) and primordial Earth (right). The surface of M-dwarf planet is illuminated by visible light. On the other hand, similar light conditions are expected underwater, since only blue-green light can penetrate meters of water. (Copyright: Astrobiology Center, NINS)
One of the most important exoplanetary biosignatures is a specific reflection pattern on the land surface named ‘red-edge’, which is caused by vegetation such as forests and grasslands. On the Earth, red-edge appears between red and infrared (IR) wavelengths, since red-light is absorbed for photosynthesis while IR radiation is reflected. In previous studies, it was predicted that red-edge position on exoplanets should be decided by the radiation spectrum by nearby stars. Around M-dwarfs, red-edge was expected to be shifted to a longer wavelength, since planets on the exoplanets use abundant IR radiation for photosynthesis. ...
Red-Edge Position of Habitable Exoplanets Around M-Dwarfs - Kenji Takizawa et al