For the first time, NASA’s James Webb Space Telescope (JWST) has captured direct images of carbon dioxide in the atmosphere of planets outside our solar system.
This exciting discovery was made in a distant planetary system called HR 8799, located 130 light-years away.
The system, which includes four giant planets, has been a key target for scientists studying how planets form.
These new images give strong evidence that the HR 8799 planets formed in a similar way to Jupiter and Saturn—by slowly building solid cores and then pulling in gas.
Until now, scientists mainly used starlight measurements to guess what exoplanet atmospheres are made of.
Webb’s new ability to directly see atmospheric gases opens up big possibilities for learning about distant worlds.
“We saw clear signs of carbon dioxide, which shows that these planets have a lot of heavy elements like carbon, oxygen, and iron,” said William Balmer, the Johns Hopkins University astrophysicist who led the research. “This supports the idea that they formed slowly, just like the giant planets in our own solar system.”
The study, also involving a system called 51 Eridani located 96 light-years away, appears in The Astrophysical Journal.
HR 8799 is a young system—only about 30 million years old—compared to our 4.6-billion-year-old solar system. Because these young planets are still hot from their formation, they glow in infrared light, which helps scientists study them more easily.
There are two main theories for how giant planets form: either they slowly build up from solid material or they quickly collapse from a disk of gas around a young star. These findings suggest that the slower, bottom-up method may be common.
To make this discovery, scientists used a special tool on Webb called a coronagraph. It works like a mini-eclipse, blocking the bright light from stars so faint planets nearby can be seen more clearly. Using this, the team captured images at infrared wavelengths that show specific gases like carbon dioxide.
They also detected HR 8799 e—the innermost of the four planets—at a new wavelength, along with 51 Eridani b. These are the first observations of these planets in these specific light bands.
This research builds on earlier JWST findings, such as a 2022 discovery of carbon dioxide in another exoplanet, WASP-39 b, using a different technique.
“These results show Webb can do what we hoped—directly observe and study planets around other stars,” said researcher Laurent Pueyo. “It’s a major step in understanding how planetary systems like ours form.”
Knowing how these giant planets form helps scientists understand how smaller, Earth-like planets survive and whether they might support life in the future.
