German astrobiologists from the Technical University of Berlin have proven that planets orbiting K-class stars may support plant and microbial life similar to that on Earth. The study was published in the scientific journal International Journal of Astrobiology (IJA).
K-class stars, or orange dwarfs, are a transitional type of star between red (M) and yellow (G) dwarfs. Our Sun belongs to the latter category. Orange dwarfs typically have 50% to 80% of the solar mass and are about twice as common as G-class stars.
Astronomers say orange dwarfs are of great interest in the search for habitable worlds because they remain stable seven times longer than solar-type stars and can shine for up to 70 billion years. They also don't typically have the powerful outbursts that red dwarfs do.
In a new experiment, scientists simulated the light of a K-class star in the lab and grew two photosynthetic organisms under it: watercress and cyanobacteria.
Watercress is a common edible green, while the cyanobacterium Chroococcidiopsis is an extremophile known for being able to lie dormant for 13 million years and remain viable.
A week later, the researchers examined the organisms and found that the watercress grew even better under the orange dwarf's radiation than under the sun's rays. The plant developed faster, its stems lengthened, and the area of its leaves increased relative to the bushes that were in standard terrestrial conditions.
Cyanobacteria showed similar behavior, showing a slightly higher integrated density compared to the solar sample.
The researchers say their discovery could speed up the search for habitable worlds in space.
