Cambridge: Astronomers have found an exoplanet more than twice the size of Earth which could be potentially habitable. This discovery might take us a step closer to search for life on planets significantly larger than Earth but smaller than Neptune.
A team from the University of Cambridge used the mass, radius and atmospheric data of the exoplanet K2-18b and determined that the planet can host liquid water at habitable conditions beneath its hydrogen-rich atmosphere. The results were reported in The Astrophysical Journal Letters.
The exoplanet K2-18b which is 124 light-years away is 2.6 times the radius and 8.6 times the mass of Earth and orbits its star within the habitable zone where temperatures could allow liquid water to exist.
The planet was the subject of significant media coverage in the autumn of 2019 as two different teams reported the detection of water vapour in its hydrogen-rich atmosphere. However, the extent of the atmosphere and the conditions of the interior underneath remained unknown.
"Water vapour has been detected in the atmospheres of several exoplanets, but even if the planet is in the habitable zone, that doesn't necessarily mean there are habitable conditions on the surface," said Dr. Nikku Madhusudhan from Cambridge's Institute of Astronomy who led the new research.
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"To establish the prospects for habitability, it is important to obtain a unified understanding of the interior and atmospheric conditions on the planet - in particular, whether liquid water can exist beneath the atmosphere," Madhusudhan added.
Given the large size of K2-18b, it has been suggested that it would be more like a smaller version of Neptune than a larger version of Earth. A 'mini-Neptune' is expected to have a significant hydrogen 'envelope' surrounding a layer of high-pressure water with an inner core of rock and iron.
If the hydrogen envelope is too thick, the temperature and pressure at the surface of the water layer beneath would be far too great to support life.