James Webb detects carbon dioxide in exoplanet atmosphere for first time
The James Webb Space Telescope has clearly detected carbon dioxide in the atmosphere of an exoplanet for the first time. The find marks a milestone for the telescope’s goal of analyzing distant planets, which could eventually help discover signs of extraterrestrial life.
One of James Webb’s key science goals is to study the composition of the atmosphere of exoplanets, with the hopes of ultimately finding ones that could host life. The main method the telescope uses to do this is transmission spectroscopy.
Essentially, every element will absorb and emit different wavelengths (or colors) of light to different degrees, resulting in a unique fingerprint. Webb can spot these fingerprints in the atmosphere of exoplanets as they pass in front of their host star, and do so with far more precision than previous telescopes. Webb first demonstrated this process in the initial data release in July, when it detected the signature of water in the atmosphere of the planet WASP-96b.
And now Webb has made a crucial detection of carbon dioxide in an atmosphere for the first time. The planet studied is WASP-39b, a gas giant abut 700 light-years away that orbits its star very closely, circling it once every four days. Though it has the mass of Saturn, it’s puffed up bigger than Jupiter, thanks to extremely high temperatures of around 900 °C (1,600 °F) that cause its atmosphere to expand.
All of these features together make WASP-39b a perfect candidate for studying the spectrum of an exoplanet atmosphere. Using Webb’s Near-Infrared Spectrograph (NIRSpec) to do so, the team detected a clear bump in the spectrum between wavelengths of 4.1 and 4.6 microns, a range that corresponds to carbon dioxide.
These new Webb observations capture the smallest differences in brightness for colors between 3 and 5.5 microns ever measured for an exoplanet. This range of the spectrum includes not just carbon dioxide but water and methane, all of which could inform the likelihood of a planet’s ability to support life. While WASP-39b isn’t likely to be a haven for life, on account of being a gas giant, the hope is that Webb’s powerful eyes could next be cast over rocky, Earth-like worlds, such as the nearby TRAPPIST-1 system.
“Detecting such a clear signal of carbon dioxide on WASP-39b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets,” said Natalie Batalha, lead scientist on the team.
The research has been accepted for publication in the journal Nature.