The James Webb Space Telescope has for the first time detected the presence of CO2 in the atmosphere of an exoplanet, i.e. a planet outside our solar system, a discovery which demonstrates its immense capabilities and excites scientists for further observations.
The planet in question is a hot gas giant where life as we know it would be impossible, but this discovery lends support to the idea that such observations can also be made on rocky planets – with the ultimate goal of determining whether one of them shelters favorable conditions for life.
“For me, it’s a door that opens for future studies of super-Earths, even Earths,” Pierre-Olivier Lagage, astrophysicist at the Atomic Energy Commission (CEA), told AFP on Thursday. and one of the many co-authors of this work, to be published in the scientific journal Nature.
“My first reaction: wow, we really have a chance of detecting the atmospheres of Earth-sized planets,” astrophysics professor Natalie Batalha of the University of California, Santa Cruz, tweeted.
The detection of CO2 will also make it possible to learn more regarding the formation of this planet, named WASP-39 b and discovered in 2011, said NASA. Located 700 light-years away, it is regarding a quarter of the mass of Jupiter, and is very close to its sun.
It was chosen because several criteria make its observation easier, at a time when scientists are still evaluating the capabilities of the telescope, which revealed its first images less than two months ago.
WASP-39 b passes very regularly in front of its sun (it goes around it in four days), and its atmosphere is extended.
For his observations, James Webb uses the transit method: when the planet passes in front of its star, he captures the tiny variation in luminosity that results.
He then analyzed the light “filtered” through the planet’s atmosphere. The different molecules present in the atmosphere leave specific signatures, which make it possible to determine their composition.
The Hubble and Spitzer telescopes had already detected water vapour, sodium and potassium in the atmosphere of this planet, but James Webb was able to go further thanks to his extraordinary sensitivity in the infrared.
In the NASA press release, Zafar Rustamkulov, of Johns Hopkins University, recounted his feelings when the presence of CO2 became clear: “It was a special moment, the crossing of a milestone in the science of exoplanets.”