A planet that orbits its star inside the habitable belt and that presents water vapor in the atmosphere has been analyzed by two teams of astronomers, a team from the Center for Space Exochemistry Data of University College London who used the telescope data space Hubble collected from 2016 to 2017, and another team led by Björn Benneke of the Institute for Research on Exoplanets at the Université de Montréal.
It is a super-earth: its dimensions, mass and consequently gravity are larger than terrestrial ones (the mass of at least eight times). However, there is the probability, as astronomers themselves point out, that the radiation it receives from its star may prove hostile to life.
K2-18b, orbiting a red dwarf located about 110 light-years away from us, has captured the interest of scientists and astronomers since its discovery. The reason is easy to say: it is a planet located in the habitable belt of its star. Now that researchers have discovered chemical signatures of water vapor in the atmosphere of this planet, interest is growing exponentially.
The water vapor in the atmosphere can in fact mean that the planet could potentially present expanses of liquid water on its surface, also formed by rain, which, combined with the fact that it is located in the habitable zone, makes it a prominent candidate for the first analyzes that will be carried out with the next James Webb space telescope.
This information suggests that on this planet there could be a water cycle similar to that of Earth, a cycle that allows water itself to condense, to form clouds and to make rain of liquid water fall.
K2-18b is the only planet, naturally among those discovered so far, to present water in the atmosphere and temperatures that can allow water to exist in liquid form on the surface. It was discovered thanks to data from NASA’s Kepler space telescope in 2015. The same data suggests that helium and hydrogen may also be present in the atmosphere.
The planet should receive roughly the same total amount of energy from its star as that which Earth receives from the Sun (the star is a small red dwarf but the planet is closer).
To date, there are hundreds of “Super-Earths” identified thanks to NASA’s two space telescopes, Kepler and TESS, and hundreds more will probably be discovered in the coming years also with the help of the James Webb space telescope which could be used in particular to analyze atmospheres of exoplanets.
The atmosphere of this planet has been the subject of two separate studies, one by a team from the University College of London published in Nature Astronomy, another by a team from the Institute for Research on Exoplanets of the University of Montreal published in the Astronomical Journal.
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