Water discovered in the atmosphere of an exoplanet located in the habitable zone of its star


For the first time, astronomers have detected water vapor in the atmosphere of a planet, K2-18b, located in the "habitable zone" of its star, a new stage in the search for signs of life beyond the solar system.

"The observations of the Hubble space telescope (conducted between 2016 and 2017, ed) have allowed us to discover that the planet has an atmosphere and that this last contains water vapor: two good news if we are interested in liveability of the planet ", explains Giovanna Tinetti, co-author of the study published Wednesday, at the AFP Nature astronomy.

"Is the Earth unique?"

"Finding water in a potentially habitable world – different from Earth – is incredibly exciting (…) and brings us closer to the answer to the fundamental question: is the Earth unique?", Welcomes Angelos Tsiaras, of the University College of London e co-author of the study.

From the data entered by Hubble in 2016 and 2017, the researchers developed algorithms to analyze the light filtered by the atmosphere of the planet. The results revealed the molecular signature of water vapor, says a statement from the University College of London.

"We cannot infer that there is liquid water on the surface of the exoplanet, but I think it is highly possible," says Giovanna Tinetti.

Furthermore, the planet is in the "habitable zone" of its star, meaning neither too close nor too far from its heat source, but precisely where the temperature allows water to exist in the liquid state and where life , as we know it, it could develop. A temperature quite similar to that of the Earth.

Located over one million billion kilometers from Earth

The adventure with K2-18b is nothing but over: now it remains to discover how much water vapor is present in the atmosphere, if there are traces of organic chemistry, oxygen and ozone .. .

Of this rare pearl, "super interesting", astronomers still know little. But what they have discovered is very promising and pushes this very distant exoplanet, located more than a million billion kilometers from the Earth, to the rank of "best candidate" for the search for signs of extraterrestrial life.

"For now the only planet we know that hosts life is the Earth, but this does not mean that to be habitable, a planet must necessarily be exactly like this," says Giovanna Tinetti. We must not put an obstacle but learn to know these worlds and "see if anyone stands out".


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