NASA’s Webb Space Telescope has clearly detected carbon dioxide in the atmosphere of an exoplanet outside the Solar System for the first time. CO2 was found in a gas giant planet orbiting a star 700 light-years from Earth.

The planet WASP-39 b is 1.3 times larger than Jupiter, but has a quarter less mass. The hot giant has a temperature of 900°C, which is not surprising since the planet is located very close to its star. It completes a full revolution, which takes a year on Earth, in just 4 days.

The planet was discovered in 2011 when it was observed partially obscuring the star’s light as it passed between it and Earth. Other NASA telescopes have proven that the atmosphere of the giant contains water vapor, sodium, and potassium. However, only the extreme sensitivity to infrared light of the Webb telescope helped to detect carbon dioxide.

Exploring the atmosphere of a planet is possible when it is in front of a star. Part of the starlight is completely obscured by the planet, and part passes through its atmosphere. Because different gases absorb different combinations of colors, researchers can analyze small differences in the brightness of the light and determine what the atmosphere is made of.

Using the NIRSpec instrument, scientists have for the first time clearly demonstrated the presence of carbon dioxide outside the solar system. No observatory has yet measured such subtle differences in the brightness of individual colors. Access to this part of the spectrum will help determine the content of gases such as methane and water vapor, as well as carbon dioxide. It is believed that they are part of the atmosphere of exoplanets of various types.

“Detecting such a clear signal of carbon dioxide on WASP-39 b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets,” says the scientist from of the University of California, who heads a group of researchers.

Understanding the composition of the atmosphere can reveal details of the planet’s origin and evolution. Scientists will be able to find out how much solid and gaseous material was involved in the formation of the planet. In the next 10 years, such studies are planned to be carried out for many other planets in order to understand how they arose.