Astronomers have finished analyzing known exoplanets and have found that land conditions in these potentially habitable worlds can be much rare than previously believed. Researchers in the project focused on the conditions required for oxygen-based photosynthesis to develop on the planet. The photosynthesis would allow a complex biosphere of the type that is located on Earth.
Scientists continue to discover more exoplanets, with the number of planets confirmed on the Milky Way, the galaxy, confirmed to be in the thousands. Astronomers say that the planets that are as much as the earth and in the living area of their host star are much less common. Currently, we are only aware of a handful of rocky and potentially habitable exoplanets in our galaxy. However, the new investigation indicates that none of those planets has the theoretical conditions to maintain a biosphere similar to the land that results from oxygenic photosynthesis.
Oxygenic photosynthesis is the mechanism that plants use to convert light and carbon dioxide into oxygen and nutrients here on Earth. The only exoplanet that approaches the reception of the stellar radiation required to hold a large biosphere is Kepler-442b. That planet is rocky, but approximately twice the dough of the earth and orbit a moderate host star. It is about 1200 light years from Earth.
Researchers in the study investigated in detail how much energy is received by a planet of their host star and if living organisms would produce nutrients and molecular oxygen efficiently, which are essential elements for complex life, since we know it. The team discovered that the stars around half the temperature of the sun can not hold the biospheres such as the earth because they do not have enough energy in the correct wavelength range.
However, oxygenic photosynthesis would still be possible on the planets orbiting those stars, but the planets could not sustain a rich biosphere. The planets that orbit a red dwarf star would not receive enough energy to support active photosynthesis. The hottest stars that the sun would emit up to 10 times more radiation than the range needed for effective photosynthesis, but does not live long enough for complex life to evolve. Since the red dwarf stars are, by far, the most common type in galaxy, the study indicates that terrestrial conditions on other planets may be much less common than previously believed.