Alien worlds are less rich in water than expected

Planets outside the Solar System are less rich in water than expected. This is indicated by the analysis of the atmosphere of 19 alien worlds, from which a very different and above all unexpected chemical composition emerges. Published in the Astrophysical Journal Letters, the result is due to the group of the British university of Cambridge coordinated by Nikku Madhusudhan.

"It is incredible to see such a low quantity of water in the atmospheres of these planets, in orbit around very different stars," observes Madhusudhan, who in 2014 had measured for the first time the quantity of water vapor in a planet outside the System Solar. "We are seeing - he adds - how the worlds outside the Solar System can be different in terms of chemical composition".

The planets analyzed in the study have very different dimensions: they go from the "mini-Neptune" with a mass almost 10 times that of the Earth to the "super-Jupiter", from the masses 600 times that of the Earth. Even their temperatures are very different and range from 20 degrees to over 2000 degrees.

The researchers identified water vapor in 14 planets and abundance of sodium and potassium in six of the 19 planets observed using space telescope data, such as NASA Hubble and European Space Agency (ESA) and NASA Spitzer, and those of land-based telescopes such as the Very Large Telescope of the Southern European Observatory (ESO) in Chile and the Canarias Grand Telescope of the Canary Islands Astrophysics Institute.

The amount of water vapor measured is surprisingly lower than expected; even the oxygen he is present in less than expected, while other chemical elements, such as sodium and potassium, are in line with expectations. Like the giant planets in our Solar System, the atmospheres of these planets are also very rich in hydrogen