No Exoplanet known to Mankind suitable to sustain life as we know it on Earth: Study

The space is boundless and eternal. However, can other planets sustain life? A new study has revealed that none of the alien planets known to humans can support life. The scientists focused on understanding the conditions needed for oxygen-based photosynthesis which allows life to flourish. Even though 1000s of planets have been discovered in our own milky way, the planets that are earth-like and in the habitable zone are much less common.

The study

At the moment, only a handful of habitable exoplanets are known to humans. The study published in Monthly Notices of the Royal Astronomical Society revealed that one exoplanet in the studied sample, Kepler-442b came close to receiving stellar radiation needed to sustain life. Kepler-442b is a super-Earth, an exoplanet, orbiting within the habitable zone of K dwarf Kepler-442, around 1,206 light-years from Earth. 

What is needed to sustain life?

To sustain life, a planet needs an Earth-like biosphere by means of oxygenic photosynthesis which plants use to convert light and carbon dioxide into oxygen and nutrients.

The study evaluated the energy these Earth-like planets acquired from their host star and if it was enough for residing organisms to  “efficiently produce nutrients and molecular oxygen” that are critical for complex life.

The researchers, by calculating the amount of photosynthetically active radiation (PAR) that a planet receives from the host star, discovered that stars that have around half the temperature of our Sun cannot encourage Earth-like biospheres. "Oxygenic photosynthesis would still be possible, but such planets could not sustain a rich biosphere", the study revealed.

Maximum stars in the galaxy are red dwarfs, which are too cool to activate photosynthesis activity on the planets, the study revealed.

"Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope," Professor Giovanni Covone of the University of Naples, lead creator of the study, said in a statement. 

"This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the "sweet spot" for hosting a rich Earth-like biosphere is not so wide," he added.