Earlier this year, WASP-39b was the subject of the first-ever detection of carbon dioxide in the atmosphere of a planet outside the solar system.
Now, in-depth analysis of data from the James Webb Space Telescope (JWST) has given us an absolute gold mine of information: the most detailed look at an exoplanet’s atmosphere to date.
The findings include information about WASP-39b’s clouds, the first-ever direct detection of photochemistry in an exoplanet’s atmosphere, and a near-complete inventory of the chemical contents of the atmosphere that reveals tantalizing hints of the exoplanet’s formation history.
These epic discoveries have been published in five papers natureand paves the way for the final disclosure of the chemical signatures of life outside the solar system.
“These early observations are a harbinger of even more amazing science to come with JWST,” says astrophysicist Laura Kreidberg, director of the Max Planck Institute for Astronomy in Germany.
“We put the telescope through its paces for performance testing, and it was almost flawless—even better than we could have hoped.”
Since the discovery of the first exoplanets in the early 1990s, we’ve sought to learn more about these worlds orbiting alien stars.
But the challenges were severe. Exoplanets can be very small and very far away. We’ve never seen most of them: we only know of their existence based on their influence on their host stars.
One such effect occurs when an exoplanet passes between us and the star, an event known as a transit. This dims the starlight slightly; Periodic darkening events indicate the presence of an object in orbit. We can even work out the size of this orbiting object, based on the dimming and gravitational effects on the star.
And one more thing we can say, based on the transfer data. When starlight passes through the atmosphere of a passing exoplanet, it changes. Some wavelengths on the spectrum are dimmer or bright, depending on how molecules in the atmosphere absorb and re-emit the light.
The signal is weak, but with a powerful enough telescope, and a set of transits, the changing absorption and emission characteristics on the spectrum can be decoded to determine the atmospheric contents of an exoplanet.
JWST is the most powerful space telescope ever launched. With three of its four instruments, it obtained detailed infrared spectra of the star WASP-39. Then the scientists began analyzing the color codes.
First was a list of particles in WASP-39b’s atmosphere. In addition to the aforementioned carbon dioxide, the researchers detected water vapor, sodium and carbon monoxide. No methane was detected, which means that WASP-39b’s metallicity is higher than that found on Earth.
It also reveals the abundance of these elements. In particular, the ratio of carbon to oxygen indicates that the exoplanet formed farther from its host star than its current close location, occupying a four-day orbit. And modeling and observational data indicate that the exoplanet’s skies are populated by fractured clouds – not of water, but of silicates and sulfates.
Finally, the observations revealed the presence of a compound called sulfur dioxide. Here in the solar system, on rocky worlds like Venus and Jovian Moon Io, sulfur dioxide is the result of volcanic activity. But in the gas worlds, sulfur dioxide has a different origin story: it is produced when hydrogen sulfide is broken down by light into its component parts, and the resulting sulfur is oxidized.
Photon-induced chemical reactions are known as photochemistry, and have implications for habitability, atmospheric stability, and aerosol composition.
To be clear, WASP-39b is unlikely to be habitable for life as we know it for a whole host of reasons, including but not limited to its scorching temperature and gaseous composition, but the discovery of photochemistry has implications for studies of the atmospheres of other worlds, and understanding the evolution of WASP-39b itself.
Planetary scientists have been preparing for years to get insights into the atmospheres JWST was expected to provide. With the first detailed analysis of the atmosphere outside the solar system, it looks like the space telescope will deliver on its promise.
In addition, the teams involved in this research are preparing documentation so that other scientists can apply their techniques to future JWST exoplanet observations.
We may not detect the signatures of life in an exoplanet’s atmosphere with JWST—perhaps a more powerful telescope would be needed to render this level of fine detail—but with WASP-39b analyzed, that discovery feels even more exciting at hand. .
“Data like this is a game-changer,” says astronomer Natalie Batalha of the University of California Santa Cruz.
The search will be published nature It can be read in the introductory prints here, here, here, here, here and here.