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The cool sub-Neptune LP 791-18 c, with an equilibrium temperature of 355 K, was found to host a hazy atmosphere, distinct from any other temperate sub-Neptune studied so far. The discovery demonstrates the intrinsic diversity of these worlds.

JWST observations of the ultra hot Jupiter WASP 121 b reveal helium escaping for most of its orbit, forming two giant tails moving in opposite directions. The results show how stellar radiation modifies planetary atmospheres.

JWST observed helium and water in the atmosphere of the giant planet WASP-107 b, revealing a vast outflow of gas and evidence for recent inward migration. The findings shed light on how giant planets lose mass and evolve over time.

The authors report on a temperate Earth-sized planet orbiting the cool M6 dwarf LP 791-18 with a radius of 1.03 ± 0.04 R_⊕ and an equilibrium temperature of 300–400 K, with the permanent night side plausibly allowing for water condensation.

JWST data show that the exoplanet WASP-18b has thermally distinct regions of its dayside. The authors mapped the sizes of these regions, measured their temperatures and potentially identify water destruction in the hottest region.

A complete revolution of exo-Neptune LTT 9779 b was observed with the NIRISS/SOSS instrument onboard the JWST. The resulting full phase curve is indicative of an equatorial jet that transports heat from the dayside to the colder nightside, resulting in an asymmetric distribution of clouds on the planet.

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%.

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 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.

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.

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 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.

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.

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.

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.

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.

A comprehensive study of the Kepler-138 system reveals the twin nature of Kepler-138 c and d and the presence of a fourth planet. Remarkably, the warm-temperate planet Kepler-138 d is probably composed of 50% volatiles by volume, indicative of a water world, rather than a rocky world, despite its small ~1.5 R_⊕ size.

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 longitudinal thermal brightness map of the super-Earth exoplanet 55 Cancri e reveals strong day–night temperature contrast, indicating inefficient heat redistribution consistent with 55 Cancri e either being devoid of atmosphere or having an optically thick atmosphere with heat recirculation confined to the planetary dayside.

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.