Astronomers discover potentially habitable exoplanet twice the size of Earth

Astronomers have discovered an exoplanet which is significantly larger than Earth but smaller than Neptune and is potentially habitable. According to the research published on the official website on February 27, a team-based at University of Cambridge used the mass, radius, and atmospheric data of the exoplanet, 'K2-18b', and determined that there is a possibility for it to host liquid water and habitable conditions beneath its hydrogen-rich atmosphere. 

The newfound exoplanet is 124 light-years away, 2.6 times of the radius and 8.6 times the mass of the Earth and it orbits its star within the habitable zone, meaning, the temperatures could allow liquid water to exist. Back in the autumn of 2019, the same planet was a matter of media coverage but the extent of the atmosphere underneath remained unknown. However, Dr Nikku Madhusudhan who led the new research at Cambridge's Institute of Astronomy said that water vapours have been detected in the atmospheres of several exoplanets but that does not imply that there are habitable conditions on the surface. 

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Madhusudhan further elaborated that, in order to establish the prospects of habitability, it is important to obtain a unified understanding of whether liquid can exist beneath the atmosphere. Furthermore, according to the size of K2-18b, the researchers have also suggested it would be like a smaller version of Neptune than a larger version of earth and referred to it as “mini-Neptune”. This exoplanet is expected to have a significant hydrogen 'envelope' surrounding the layer of high-pressure water with an inner core of rock and iron.

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Thickness of hydrogen envelope

However, the main concern of the astronomers was if the hydrogen envelope around mini-Neptune was too-thick or thin enough to support life. But, now Madhusudhan and his team have confirmed that the atmosphere instead, is thin, therefore the water layer could have the right conditions to support life. Using detailed numerical models and satistical methods to explain the data, the researchers have determined the composition and structure of both exterior and interior. They have also found chemicals like methane and ammonia are at a lower level than expected for its atmosphere. This study has now opened the search for habitable conditions and bio-signatures outside the solar system to exoplanets. 

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