The James Webb Space Telescope (JWST) has achieved a groundbreaking feat by directly observing carbon dioxide (CO2) in the atmospheres of exoplanets for the very first time. Announced by NASA on March 17, 2025, this achievement comes from a series of observations made in the HR 8799 system, located 130 light years away from Earth.
New Method of Observation
What makes this discovery particularly significant is the method used to detect CO2—direct imaging. Typically, astronomers detect exoplanets when they pass in front of their host stars, causing a temporary dimming of the star’s light.
This “transit method” has already allowed Webb to indirectly detect CO2 on exoplanets, such as the gas giant WASP-39 in 2022. However, in the case of the HR 8799 system, Webb’s coronagraph instruments allowed scientists to block out the light from the bright stars and directly observe the emitted light from the planets themselves.
This method represents a huge leap forward in exoplanetary research. Lead study author William Balmer, an astrophysicist at Johns Hopkins University, compared it to using a flashlight to spot fireflies near a lighthouse : “It’s like putting your thumb up in front of the sun when you’re looking up at the sky.”
Yet, Webb‘s ability to directly detect the light from these exoplanets has provided a wealth of new data, including the key chemical signature of CO2 in the planets’ atmospheres.
Are Moons the Key?
While the gas giants in the HR 8799 system are unlikely to support life due to their extreme environments, the discovery of CO2 has significant implications for understanding planetary formation.
According to the study published in The Astrophysical Journal, the new data suggests that these planets might have formed in a similar way to Jupiter and Saturn, through a “bottom-up” process where icy particles come together to form a solid core.
Scientists believe that the moons orbiting these gas giants could be more promising candidates for hosting life. Just as some moons of Jupiter, like Europa, are thought to harbor vast oceans beneath icy surfaces, moons around these exoplanets might also possess the conditions necessary for life to exist.
Current missions investigating the potential for life on Europa and other moons are a step in this direction, raising hope that life could exist elsewhere in the universe—albeit in ways very different from what we know on Earth.
What’s Next for Exoplanet Exploration?
This new discovery is a huge step in exoplanetary research, but it is just the beginning. Researchers are eager to study smaller, Earth-like planets, as these are more likely to support life.
Webb’s findings in the HR 8799 system will likely pave the way for future missions focused on these smaller planets. In 2027, NASA’s Nancy Grace Roman Space Telescope will launch, equipped with a coronagraph to study these Earth-sized worlds in more detail.
