By spotting these strong carbon dioxide features, we have shown there is a sizable fraction of heavier elements, like carbon, oxygen, and iron, in these planets’ atmospheres,” said William Balmer, of Johns Hopkins University in Baltimore.

In 2022, the Webb telescope detected unequivocal evidence of carbon dioxide in the atmosphere of a distant exoplanet called WASP-39b. But that detection was made indirectly, so the latest accomplishment newly validates the telescope’s ability to spot the gas in distant star systems.