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The transmission spectrum of the super-Earth exoplanet GJ 1214b is observed to be featureless at near-infrared wavelengths and its atmosphere must contain clouds to be consistent with the data.

The detection of thermal emission from the rocky exoplanet TRAPPIST-1 c using the Mid-Infrared Instrument on the James Webb Space Telescope reveals a dayside brightness temperature that disfavours a thick, CO₂-rich atmosphere.

A population study of near-infrared spectra of 19 hot giant planets shows a correlation between the strength of the 1.4 μm water band and temperature, which is broadly regulated by irradiation. However, the observed scatter around the mean is indicative of the effect of individual planetary formation pathways on the composition.

A giant planet candidate roughly the size of Jupiter but more than 14 times as massive is observed by TESS and other instruments to be transiting the white dwarf star WD 1856+534.

Analysis of the cool brown dwarf Gliese 229 B suggests that it is actually a close binary of two less massive brown dwarfs, explaining its low luminosity and settling the conflict between theoretical predictions and measurements.

Phase-resolved mid-infrared observations from JWST of the hot gas giant WASP-43b detect a day–night difference of 659 ± 19 K. Comparison with climate models shows that the observations are compatible with cloudy skies, at least on the nightside, and the lack of methane detection suggests the presence of disequilibrium chemistry.

The medium-resolution transmission spectrum of the exoplanet WASP-39b, described using observations from the Near Infrared Spectrograph G395H grating aboard JWST, shows significant absorption from CO₂ and H₂O and detection of SO₂.

The transmission spectrum of the exoplanet WASP-39b is obtained using observations from the Single-Object Slitless Spectroscopy mode of the Near Infrared Imager and Slitless Spectrograph instrument aboard the JWST.

The dayside thermal emission spectrum and brightness temperature map of the ultra-hot Jupiter WASP-18b obtained from the NIRISS instrument on the JWST showed water emission features, an atmosphere consistent with solar metallicity, as well as a steep and symmetrical decrease in temperature towards the nightside.

Observations from the JWST MIRI/LRS show the detection of SO₂ spectral features in the 5–12-μm transmission spectrum of the hot, Saturn-mass exoplanet WASP-39b, suggesting that photochemistry is a key process in high-temperature exoplanet atmospheres.

Time-series observations from the JWST of the transiting exoplanet WASP-39b show gaseous water in the planet’s atmosphere and place an upper limit on the abundance of methane.

The atmospheric terminator region of WASP-39 b, a hot gas giant exoplanet, is inhomogeneous, despite past assumptions, with the evening terminator being hotter and thus probably clearer, and the morning terminator probably being cloudy and consequently cooler.

A combined analysis of datasets across four JWST instrument modes provides a benchmark transmission spectrum for the Saturn-mass WASP-39 b. The broad wavelength range and high resolution constrain orbital and stellar parameters to below 1%.

A broad-wavelength 0.5–5.5 µm atmospheric transmission spectrum of WASP-39b, a 1,200 K, roughly Saturn-mass, Jupiter-radius exoplanet, demonstrates JWST’s sensitivity to a rich diversity of exoplanet compositions and chemical processes.

Observations from the JWST show the presence of a spectral absorption feature at 4.05 μm arising from SO₂ in the atmosphere of the gas giant exoplanet WASP-39b, which is produced by photochemical processes and verified by numerical models.

Transmission spectroscopy observations from the James Webb Space Telescope show the detection of carbon dioxide in the atmosphere of the gas giant exoplanet WASP-39b.

A detection of helium absorption at 10,833 Å on the exoplanet WASP-107b reveals that its atmosphere is extended and eroding, and demonstrates a new way to study upper exoplanetary atmospheres.

A two-year study of mercury deposition in the Arctic finds that the main source of mercury is gaseous elemental mercury, which is deposited throughout the year and leads to very high soil mercury levels.

The JWST has the potential to increase our understanding of terrestrial exoplanets and their atmospheres, but the various signal contaminations need to be isolated and quantified. Using JWST Cycle 1 observations of TRAPPIST-1 as a benchmark, this Perspective proposes a series of steps to use future JWST data efficiently for this purpose.