The James Webb Space Telescope has delivered a spectacular scientific result. For the first time, carbon dioxide has been clearly detected in the atmosphere of an exoplanet. Teams from the universities of Geneva, Bern and the national research center PlanetS took part in the discovery.
This is exceptional, because until now, the components detected in the atmospheres of exoplanets have been limited. For the first time in history, CO2 has been detected and can be measured: “It is as important as the detection of water, methane or molecular oxygen”, explains Monika Lendl, co-author of the study, professor in the Department of Astronomy of the UNIGE and member of the NCCR PlanetS national research center.
This marks a new step in the search for life in the universe, as carbon dioxide plays a key role in regulating the climate; it is notably a central component of our Earth’s atmosphere.
Finding this gas so clearly is an essential step in the search for worlds that might harbor life: “To find life, it will be necessary to study smaller planets, because this one is too big, too gaseous, has too much pressure and is far too hot – it’s 1000 degrees there!”, remarks the researcher by telephone, to RTSinfo. “It’s not habitable at all, it’s hell”.
Fingerprints
The exoplanet WASP-39 b is a “hot Jupiter”, a burning gas giant that orbits around its star. The latter, similar to the Sun, is located 700 light years from Earth. When a planet passes right in front of its star – astronomers call this phenomenon a transit –, part of the light from the star passes through the atmosphere of the planet before reaching the telescope.
>> The light curve of the transit of WASP-39 b on July 10, 2022:
A series of light curves from NIRSpec, JWST’s near-infrared spectrograph, show the change in brightness of three different wavelengths (colors) of light from the WASP-39 star system over time as the planet transited in front of its star, on July 10, 2022. [Illustration: NASA, ESA, CSA, and L. Hustak (STScI) – Science: The JWST Transiting Exoplanet Community Early Release Science Team]
“The atmosphere then filters certain colors more than others, depending on the material that composes it, its thickness and the presence or not of clouds”, indicates Monika Lendl.
“By using the James Webb Telescope (JWST) to break light down into its colors, we can identify characteristic ‘fingerprints’ of different gases and determine the composition of the atmosphere,” she says. (read box). Using NIRSpec, JWST’s near-infrared spectrograph, the research team was able to detect the fingerprint of carbon dioxide in the light passing through WASP-39b’s atmosphere.
>> Transmission spectrum of the giant hot gas exoplanet WASP-39 b:
A transmission spectrum of the giant hot gas exoplanet WASP-39 b captured by NIRSpec, the near-infrared spectrograph at JWST, on July 10, 2022. It reveals the first clear evidence for the presence of carbon dioxide in the atmosphere from a planet outside the solar system. It is also the first detailed exoplanet transmission spectrum ever captured that covers wavelengths between 3 and 5.5 microns. [Illustration: NASA, ESA, CSA, and L. Hustak (STScI) – Science: The JWST Transiting Exoplanet Community Early Release Science Team]
Understanding formation and evolution
“As soon as we saw the data, it was clear that we were dealing with a spectacular discovery”, explains Dominique Petit dit de la Roche, researcher at UNIGE, co-author of the study and member of PlanetS.
Understanding the composition of a planet’s atmosphere helps to better understand the origin of the planet and its evolution. WASP-39 b orbits its star in a narrow orbit, which is one-eighth the distance between our Sun and Mercury; it only takes a little over four Earth days to complete one revolution.
This planet is subjected to intense radiation which heats it to a very high temperature: its atmosphere is very dilated. Its size is one-third larger than Jupiter, which is the largest gas giant in our solar system.
This discovery shows that, in the future, the Webb telescope may be able to detect and measure carbon dioxide in the thinner atmospheres of smaller rocky planets: “To infer the presence of life, the detection of CO2 will not be enough: it will take the combination of other tracers”, underlines Monika Lendl.
Stéphanie Jaquet and the ats
