James Webb detects carbon dioxide directly on exoplanets for the first time

The James Webb Space Telescope (JWST) has for the first time directly detected carbon dioxide on four planets outside our solar system. The observations indicate that they were formed similarly to the gaseous planets in our solar system.

The planets orbit the star HR 8799, which is around 130 light years away from Earth. Like many of the exoplanets discovered so far, these are also comparatively young – young celestial bodies are still hot and therefore emit a clearly visible infrared signature. The HR 8799 system is just 30 million years old – For comparison: our solar system was formed 4.6 billion years ago.

The planets are gas giants like Saturn and Jupiter. However, they are significantly more massive: the smallest has seven times the mass of Jupiter, the largest ten times. In addition, they orbit their star at a much greater distance: 15 to 70 times the distance between Jupiter and the sun.

Analyzing the chemistry of planetary atmospheres

JWST observed the system in the infrared spectrum. Not only were images of the planets taken, but the chemistry of their atmospheres was also analyzed. Among other things, the researchers found carbon dioxide in greater quantities than expected.

“With the discovery of these strong carbon dioxide features, we have shown that there is a significant amount of heavier elements such as carbon, oxygen, and iron in the atmospheres of these planets,” said William Balmer, an astrophysicist at Johns Hopkins University. “Given what we know about the star they orbit, this probably suggests that they were formed by core accretion, which is an exciting conclusion for planets we can see directly.”

Gas planets form quickly or slowly

Gas giants can form in two ways: quickly, by the collapse of a gas cloud, or slowly, by the formation of a core of rock and metal that gravitationally attracts gas. The large quantities of heavy elements discovered on the planets indicate slow formation — as with the gaseous planets from our solar system.

“Our hope in this kind of research is to understand our own solar system, life and ourselves compared to other systems with exoplanets, so we can put our existence in context,” Balmer said. “We want to take images of other solar systems and compare whether they are similar to or different from our system. From that, we can try to get a sense of how weird our solar system really is — or how normal.”

The team has published its findings in The Astronomical Journal.

(wpl)