The James Webb Space Telescope Observations of WASP-39b: The First Detection of Carbon Dioxide on an Exoplanet
This world we know most about after the eight major planets of our Solar System is made up of the most detailed information ever produced on a exoplanet by the James Webb Space Telescope. Observations of the planet, called WASP-39b, reveal patchy clouds, an intriguing chemical reaction in its atmosphere, and provide hints about its formation.
What researchers have seen so far is preliminary and doesn’t yet indicate what sorts of atmospheres these planets might actually have. But if they have dense atmospheres with intriguing molecules such as carbon dioxide or methane, the US$10-billion telescope will be able to detect them in the coming months and years. It has been impossible to spot the atmospheres at other observatory.
The telescope looked at the planet for over 40 hours in July. Initial results showed carbon dioxide in the planet’s atmosphere. It was the first time that the gas had been seen on an exoplanet.
“These spectra are just exquisite in their detail, and reveal an additional way that the star affects the planet’s atmospheric composition, through photochemistry,” says Victoria Meadows, an astronomer at the University of Washington in Seattle.
Such inward migration of hot Jupiters is expected, to explain their proximity to their stars. Whether this is a slow process, over the course of tens of millions of years, or whether it’s a result of some kind of planet or star hitting it, remains to be seen. Knowing WASP-39b’s composition can help determine which scenario occurred.
The attraction between the two stars is so great that the planet is locked to its star, with the same face pointing towards it. And the observations show that it has incomplete cloud cover — something that astronomers have never observed before on an exoplanet. The planet is covered by only 60% of clouds at the boundary of night and day, according to Bean, possibly due to the way clouds evaporate when they reach the hotter side.
The First Look at TRAPPIST-1g: A Molecular Planet with a Dense Atmosphere? An Astronomer’s Perspective
The first results from the JWST were released on December 13th, but an astronomer at the University of Montreal said they are in business.
One of the observations taken last week that she hasn’t seen yet in the crush of JWST results is a TRAPPIST-1 planet. “It’s hectic,” she says.
Benneke was the one showing the first TRAPPIST studies. The telescope can make out that it probably doesn’t have a hydrogen-rich atmosphere because it is so large. It could be that the planet has a dense atmosphere composed of heavier molecule such as carbon dioxide or no atmosphere at all.
“We needed this first look to know what we’re dealing with,” says Knicole Colón, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in the work. Benneke declined to speak with reporters about the TRAPPIST-1g results, citing a paper under review at a scientific journal.
Exploring Planetary Formation with High-Energy Photons: Results from the Joint Wide-Field Telescope (JWST) Experiment
The limits of this habitability need to be explored. The finding is a small step towards understanding how photochemistry protects planets from high-energy irradiation. The parameters used in models of planetary formation can be tightened. Both advances pave the way to future observations of planets that are similar to Earth.
The three instruments used in the studies all have wavelength ranges that allow them to look for features of the key atmospheric molecule reported. But each instrument has different configurations that enable access to different wavelength ranges and spectral resolving powers. Rustamkulov et al., Alderson et al. Two configurations of an instrument called Near the IR were used by Ahrer et al. Ahrer et al.5 used a device known as the NearInfrared Camera, while also using a Slitless Spectrograph. Between them, the teams observed light with wavelengths spanning 0.5 to 5.5 micrometres (Fig. 1).
Data-processing techniques were used to move each instrument’s data to the final spectrum. And although these efforts returned mostly similar results, the diverse approaches show that there is no consensus yet on the optimal way to process JWST data — indeed, there is much still to learn. Some problems have already begun to be addressed in these initial studies, including how best to manage pixels that are saturated1 (giving unreliable signals), and what to do when mirror segments spontaneously tilt during observation2.
More discoveries are sure to come. Other research teams have been using JWST to study TRAPPIST-1b, as well as other planets in the system. That includes TRAPPIST-1b’s neighbor, TRAPPIST-1c, a planet that is close enough to its star for JWST to study its glow. Publications on these are about to be published.