Just because a planet is in its star’s Goldilocks zone doesn’t mean it’ll be capable of supporting an Earth-like biosphere. A new study focuses on the amount of radiation in the wavelengths usable by photosynthetic plants; “the team discovered that stars around half the temperature of our Sun cannot sustain Earth-like biospheres because they do not provide enough energy in the correct wavelength range. Oxygenic photosynthesis would still be possible, but such planets could not sustain a rich biosphere.” Red dwarfs—where many exoplanets have been discovered—have only a third the Sun’s temperature; stars that are brighter and hotter than the Sun have lifespans too short for life to have a chance to evolve. In other words, the Sun is in a very narrow sweet spot. [Universe Today]