Carbon dioxide has been conclusively detected in the atmosphere of an exoplanet for the first time—and at the first time of asking.
The gas—an important component of Earth’s atmosphere—was discovered on July 10, 2022 by the James Webb Space Telescope (JWST) in the atmosphere of WASP-39b, a hot gas-giant orbiting a Sun-like star about 700 light-years from Earth.
WASP-39b was the first exoplanet JWST made an official observation of.
It adds another wonderful discovery to add to JWST’s already incredible achievements, which include imaging the most distant star known thanks to a ripple in space-time, showing Jupiter like never before and revealing previously unseen gas and dust in spectacular spiral galaxies.
“From the first glance at the data it was already clear that we were dealing with a spectacular discovery,” says Dominique Petit dit de la Roche, researcher at the University of Geneva, co-author of a study published today in Nature and member of the National Centre of Competence in Research (NCCR) PlanetS. “For the first time, carbon dioxide has been clearly detected on a planet outside the solar system.”
The discovery indicates that the Webb space telescope can spot key molecules like carbon dioxide in a wide variety of exoplanets, which will give scientists new insights into the composition, formation and evolution of planets across the galaxy.
However, this bloated planet is not like Earth. WASP-39b orbits much closer to its star than Mercury does to the Sun and it’s about a third larger than Jupiter, according to the authors. It also heats up to around 900°C.
So why is this discovery so important?
Largely overlooked in JWST’s “first light” images in July 2022 was data showing the existence of water, along with evidence for clouds and haze, in the atmosphere of an exoplanet called WASP-96 b, which orbits a Sun-like star. It was found using JWST’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument. This new discovery of carbon dioxide at WASP-39 is yet more proof that this cutting-edge science instrument works perfectly.
“Detecting such a clear signal of carbon dioxide on WASP-39b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets as well as for measuring abundances of other gases like water and methane,” said Natalie Batalha of the University of California at Santa Cruz, leader of the international research team that carried out the observations.
NIRISS only works when an exoplanet passes directly in front of its host star. When that happens some of the star’s light passes through the planetary atmosphere before it reaches the telescope. “The atmosphere filters out some colors of this light more efficiently than others, depending on factors such as its composition, its thickness and its cloud content,” said Monika Lendl, study co-author, astronomy professor at the University of Geneva and member NCCR PlanetS.
Researchers can then break down light into its colours to identify characteristic “fingerprints” of different gases and chemicals present in a planet’s atmosphere-such as carbon dioxide.
Understanding the composition of a planet’s atmosphere also allows insights into the origin of the planet and its evolution. “Carbon dioxide molecules are sensitive tracers of the story of planet formation,” said Elspeth Lee, co-author of the study, Ambizione fellow at the University of Bern and member of the NCCR PlanetS. “The clear detection of carbon dioxide in WASP-39b gives us information about the inventory of carbon and oxygen molecules in the atmosphere.”
Webb is the most ambitious and complex space science telescope ever constructed, with a massive 6.5-meter primary mirror that will be able to detect the faint light of far-away stars and galaxies. It’s designed solely to detect infrared light emitted by distant stars, planets and clouds of gas and dust.
It’s initial 10-year mission Webb will study the solar system, directly image exoplanets, photograph the first galaxies and explore the mysteries of the origins of the Universe.
Wishing you clear skies and wide eyes.