Photosynthesis changed Earth in powerful ways. When photosynthetic organisms appeared, it led to the Great Oxygenation Event. That allowed multicellular life to evolve and resulted in the ozone layer. Life could venture onto land, protected from the sun's intense ultraviolet radiation.
But Earth's photosynthetic organisms evolved under the sun's specific illumination. How would plants do under other stars?
Our sun is a G-type star, sometimes called a yellow dwarf. It seems like a normal star to us, but yellow dwarfs aren't that common. Only about 7% to 8% of stars in the Milky Way are G-type stars. When it comes to understanding habitability on exoplanets, we need to understand the more plentiful types of stars.
Some scientists propose that K-dwarf stars are the most optimal host stars for habitable exoplanets. They're between about 50% and 80% as massive as G-type stars, are more abundant and have stable luminosities for billions of years longer than sun-like stars.
The sun will be stable on the main sequence for about 10 billion years, while K-type stars can be stable for up to 70 billion years. Despite this, much exoplanet habitability research focuses on M-dwarfs, or red dwarfs, which may actually be far more inhospitable to life because of flaring and tidal locking.
In a new study, a trio of researchers simulated the light output from a K-dwarf star and grew two photosynthetic organisms in those conditions to see how they responded. The research article is "Observation of significant photosynthesis in garden cress and cyanobacteria under simulated illumination from a K dwarf star." It's published in the International Journal of Astrobiology, and the lead author is Iva Vilović, a Ph.D. student in the Astrobiology Research Group at the Technical University of Berlin.
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