Scientists have identified 29 exoplanets that are perfectly positioned that could possibly host life aside from Earth. However, a new study suggests that planets with Earth-like biosphere in the Milky Way could be rarer than previously thought.

The study, entitled "Efficiency of the oxygenic photosynthesis on Earth-like planets in the habitable zone" published in Monthly Notices of the Royal Astronomical Society, found that only Kepler-442b receives enough sunlight from its star to form a biosphere with "oxygenic photosynthesis," a crucial process to support life.

According to MailOnline, researchers believe that all known exoplanets, except for Kepler-442b, are well below the threshold. Hence, photon flux in these exoplanets would probably fail to host an atmosphere that is similar to Earth's.

 Exoplanets with Earth-Like Biosphere Are Fewer Than Previously Thought, Study Suggests
(Photo : Wikimedia Commons)
Size comparison Kepler-442b and Earth

Testing for Oxygenic Photosynthesis in Exoplanets

According to ScienceAlert, researchers from the University of Naples Federico II and INAF Capodimonte Astronomical Observatory in Italy studied the levels of sunlight that ten exoplanets receive from their star. Unfortunately, they failed to find a single planet that has an atmosphere that matches Earth's.

Growing a simple garden on Earth demands ample sunlight for plants to thrive. It takes the oxygenic photosynthesis process to generate reactions that could help them grow.

Researchers wanted to test whether their assumption that oxygenic photosynthesis is crucial in determining if a planet could host life. They measured the light falling across different exoplanets and the spread of wavelengths that make up the radiation. They also calculated the level of "exergy, the amount of energy that could be harvested out of the sunshine.

But most of the stars of these exoplanets are red dwarfs, which can release furious solar winds that could quickly strip a planet's atmosphere. Due to that, researchers found that Earth-like planets may be much less common than scientists have hoped.

On the other hand, a star as bright as the Sun could encourage photosynthesis, which makes a living biosphere possible. among the exoplanets identified in the study, none of them are capable of fueling enough photosynthesis like Earth, except for one.

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What Exoplanets Can Support Life?

Out of the exoplanets studied in the new research, the team found that only the Keppler-442b receives enough sunshine from its star to form a biosphere with oxygenic photosynthesis.

According to NASA, Kepler-442b is considered a "Super-Earth", having a radius of 1.34 times that of Earth and more than twice its mass. This rocky planet was discovered in 2015, which takes roughly 112.3 days to complete one revolution and is 0.409 AU (astronomical units) away from its star. Kepler-442b is approximately 1,200 light-years away from Earth in the constellation Lyra, located in the habitable zone known as the Goldilocks zone.

Kepler-442b orbits a star that is 60% the mass of the Sun. Its rotation allows it to shed heat, which makes it look like a potential paradise that could possibly host life.

As the knowledge on Earth-like planets grows, scientists are hoping to uncover better exoplanets that have atmospheres like the Earth.


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