The idea of finding other Earth-like planets or a planet outside our solar system teeming with alien life has always excited the astronomers.
And the same curiosity led to the discovery of the first exoplanet in the 1990s. From then, thisvnumber has exploded to more than 4,000 confirmations, with thousands of other "candidates” awaiting confirmation.
Previous year a paper claimed that there may be 300 million planets in our galaxy that are potentially habitable. While, the new research published in the Monthly Notices of the Royal Astronomical Society staggers that view.
This analysis of known exoplanets focuses on photosynthesis and suggests that the Earth-like conditions on potentially habitable planets may be much rarer than previously thought.
Over four thousand exoplanets have been discovered thus far by astronomers, but only few or handfuls are considered to be potentially habitable. Photosynthesis is the process in which plants uses sunlight, water and carbon dioxide to create food and release oxygen and energy into the atmosphere.
Photosynthesis is critical in enabling complex biospheres of the type found on Earth. Therefore for an exoplanet to be potentially habitable, it will develop an oxygen-based atmosphere. Later this year, the launch of the James Webb Space Telescope (JWST) which will be able to study the atmospheres of exoplanets as they revolve around their stars.
And, the light that comes through their atmosphere will reveal what gases the exoplanets contain. Although photosynthesis requires liquid water but only those have the right temperature which not too hot or too cold can host such a thing on their surface.
The research also studies the amount of sunshine each promising exoplanet receives from its star. This reveals that only one planet that comes close to receiving enough sunshine to sustain a large biosphere that could be detected by JWST is Kepler−442b.
Kepler-442b is a rocky planet which is about twice the mass of the Earth which orbits around a moderately hot orange dwarf star, around 1,120 light years away in the constellation of Lyra.
Kepler-442b also called KOI-4742.01 existence was announced in 2015 having been discovered by the Kepler Space Telescope which stopped working in 2018.
This exoplanet is about half the distance from its star that the Earth is from the Sun and takes 112 days to orbit the star. The analysis concludes that stars around half the temperature of the Sun cannot sustain Earth-like biospheres as they don't provide enough energy in the correct wavelength range.
To which, this doesn’t mean that photosynthesis would be impossible but there won’t be enough plant life on the planet to sustain an Earth-like biosphere.