With WASP-39b, the James Webb Telescope is paving the way for archaeologists in the Universe

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The first observation of an exoplanet’s atmosphere by the James Webb Space Telescope, published on Thursday, revealed the presence of CO2 around WASP-39b. This first detection of this chemical compound outside our solar system confirms that the telescope will make it possible to understand the formation of the most distant planets.

Mankind so far has not noticed anything outside of our solar system. At least not in a way. The observations of the James Webb space super-telescope (JWST) brought, Thursday, August 25, the definitive proof. For the first time, carbon dioxide has been detected in the atmosphere of an exoplanet (ie outside the solar system).

The giant eye of the new telescope, launched on December 25, 2021, looks around our galaxy to look for traces of CO.2. He found some around the planet WASP-39b which is “only” about 700 light years from Earth. It is only a few blocks of stardust away from us compared, for example, to the CEERS-93316 galaxy detected by the James Webb instrument in early August more than 13 billion light-years from Earth.

The first device capable of “seeing” CO2 is in the air

“We doubt we will find the CO2but it is always good to have confirmation that JWST actually allows us to identify this important molecule in the atmosphere of an exoplanet”, said Hannah Wakeford, astrophysicist at the University of Bristol, member of the international research team that wrote of the results from the WASP-39b sighting, which will be published in the journal Nature on August 29.

The Hubble telescope, followed by James Webb, has already observed in 2008 what CO looks like.2 in the atmosphere of an exoplanet, but “it is only a sign that suggests the presence of carbon dioxide”, says Jérémy Leconte, astrophysicist at the University of Bordeaux who is also a member of the team that made the observations of WASP-39b . “There, when we saw the readings transmitted by JWST, there was no possible doubt,” he added.

“Until now, we don’t have the tools to know for sure the presence of CO2“, explains Hannah Wakeford. The JWST is, in fact, the first space observation instrument capable of detecting some infrared wave frequencies. a different way, which gives it a particular signature of telescope readings”, details Jérémy Leconte.

And this is not the first time that the CO2 found in the atmosphere of an exoplanet. This is also the first confirmation of the presence of this molecule in a WASP-39b type planet, that is, a gas giant similar to Jupiter, all galaxies combined… including our solar system. This, in fact, never proved that there was anything on Jupiter or Saturn.

Co2a “bad sign of the presence of life in space”

Seen from Earth, this discovery of carbon dioxide in WASP-39b can easily give rise to fantasies of the presence of life. This is because of our planet, CO emissions2 in the atmosphere mostly from living organisms. This can be done during the decomposition of organic matter or from animal respiration.

But the extra-terrestrial hunters set their nets on the little green people. “The presence of CO2 in the atmosphere of a planet is, in fact, a bad sign of the presence of life”, affirms Hannah Wakeford. The atmosphere of Venus, for example, is full of carbon dioxide while it is about a planet that is particularly hostile to all forms of life, if only because of the very high surface temperature (over 400°C).

WASP-39b also experiences extreme temperatures, reaching 900°C, in its atmosphere. Where does CO come from?2 ? “This is the result of a chemical reaction when carbon, hydrogen and helium are mixed – all the elements present in the atmosphere of this exoplanet – at very high temperatures”, explains Jérémy The tale.

The holy grail for space archaeologists

Detecting CO2 is important to astrophysicists because “it’s a very good indicator for understanding the history of a planet”, says Hannah Wakeford. The presence of this molecule gives, first of all, “a serious indication that the planet has an atmosphere”, which is far from the situation of all the planets in the Universe (in our own solar system, Mercury does not have an atmosphere). And the atmosphere stores the chemical traces of all the planet’s history.

Thus, the data transmitted by JWST on the atmosphere of WASP-39b – and in particular the concentration of CO2 – We are now allowed to make a first observation: this planet is from somewhere else. In fact, it is currently very close to its star – similar to our sun, according to the experts interviewed – and “it is physically impossible that by staying there it could accumulate a lot of CO.2 and oxygen in its atmosphere”, assures Hannah Wakeford. For her, there are not 1001 possibilities: WASP-39b has “recovered elements of CO2 and oxygen while moving from its place of formation to its present position”.

These first JWST observations of the atmosphere of an exoplanet made it possible to confirm “that it is really possible to do this kind of analysis and search for molecules like CO.2“, enthuses Jérémy Leconte. In this respect, this device is indeed, for Hannah Wakeford, the long-awaited Holy Grail of space archeology. With a “terra-centric” approach, because the goal is to JWST to reproduce the sites of tens of hundreds of exoplanets to understand their formations and, finally, to know how unique our Earth is in the Universe.

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