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Transmission spectroscopy has been a workhorse technique used over the past two decades to constrain the physical and chemical properties of exoplanet atmospheres1–5. One of its classical key assumptions is that the portion of the atmosphere it probes—the terminator region—is homogeneous. Several works from the past decade, however, have put this into question for highly irradiated, hot (Teq ≳ 1,000 K) gas giant exoplanets, both empirically6–10 and through three-dimensional modelling11–17. While models have predicted clear differences between the evening (day-to-night) and morning (night-to-day) terminators, direct morning and evening transmission spectra in a wide wavelength range have not been reported for an exoplanet so far. Under the assumption of precise and accurate orbital parameters for the exoplanet WASP-39 b, here we report the detection of inhomogeneous terminators on WASP-39 b, which has allowed us to retrieve its morning and evening transmission spectra in the near-infrared (2–5 μm) using the James Webb Space Telescope. We have observed larger transit depths in the evening, which are, on average, 405 ± 88 ppm larger than the morning ones, and also have qualitatively larger features than the morning spectrum. The spectra are best explained by models in which the evening terminator is hotter than the morning terminator by 17 7 − 57 + 65 K, with both terminators having C/O ratios consistent with solar. General circulation models predict temperature differences broadly consistent with the above value and point towards a cloudy morning terminator and a clearer evening terminator.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. [ABSTRACT FROM AUTHOR]

As the closest transiting hot Jupiter to Earth, HD 189733b has been the benchmark planet for atmospheric characterization1–3. It has also been the anchor point for much of our theoretical understanding of exoplanet atmospheres from composition4, chemistry5,6, aerosols7 to atmospheric dynamics8, escape9 and modelling techniques10,11. Previous studies of HD 189733b have detected carbon and oxygen-bearing molecules H2O and CO (refs. 12,13) in the atmosphere. The presence of CO2 and CH4 has been claimed14,15 but later disputed12,16,17. The inferred metallicity based on these measurements, a key parameter in tracing planet formation locations18, varies from depletion19,20 to enhancement21,22, hindered by limited wavelength coverage and precision of the observations. Here we report detections of H2O (13.4σ), CO2 (11.2σ), CO (5σ) and H2S (4.5σ) in the transmission spectrum (2.4–5.0 μm) of HD 189733b. With an equilibrium temperature of about 1,200 K, H2O, CO and H2S are the main reservoirs for oxygen, carbon and sulfur. Based on the measured abundances of these three main volatile elements, we infer an atmospheric metallicity of three to five times stellar. The upper limit on the methane abundance at 5σ is 0.1 ppm, which indicates a low carbon-to-oxygen ratio (<0.2), suggesting formation through the accretion of water-rich icy planetesimals. The low oxygen-to-sulfur and carbon-to-sulfur ratios also support the planetesimal accretion formation pathway23.The exoplanet HD 189733b has a metal-enriched atmosphere with the possible presence of H2O (13.4σ), CO2 (11.2σ), CO (5σ) and H2S (4.5σ). [ABSTRACT FROM AUTHOR]

Close-in giant exoplanets with temperatures greater than 2,000 K (‘ultra-hot Jupiters’) have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from the Hubble Space Telescope (HST) and Spitzer Space Telescope1–3. However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information content of the data resulted in high sensitivity to the varying assumptions made in the treatment of instrument systematics and the atmospheric retrieval analysis3–12. Here we present a dayside thermal emission spectrum of the ultra-hot Jupiter WASP-18b obtained with the NIRISS13 instrument on the JWST. The data span 0.85 to 2.85 μm in wavelength at an average resolving power of 400 and exhibit minimal systematics. The spectrum shows three water emission features (at >6σ confidence) and evidence for optical opacity, possibly attributable to H−, TiO and VO (combined significance of 3.8σ). Models that fit the data require a thermal inversion, molecular dissociation as predicted by chemical equilibrium, a solar heavy-element abundance (‘metallicity’, M/H = 1.0 3 − 0.51 + 1.11 times solar) and a carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside brightness temperature map, which shows a peak in temperature near the substellar point that decreases steeply and symmetrically with longitude towards the terminators.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. [ABSTRACT FROM AUTHOR]

There are no planets intermediate in size between Earth and Neptune in our Solar System, yet these objects are found around a substantial fraction of other stars1. Population statistics show that close-in planets in this size range bifurcate into two classes on the basis of their radii2,3. It is proposed that the group with larger radii (referred to as ‘sub-Neptunes’) is distinguished by having hydrogen-dominated atmospheres that are a few percent of the total mass of the planets4. GJ 1214b is an archetype sub-Neptune that has been observed extensively using transmission spectroscopy to test this hypothesis5–14. However, the measured spectra are featureless, and thus inconclusive, due to the presence of high-altitude aerosols in the planet’s atmosphere. Here we report a spectroscopic thermal phase curve of GJ 1214b obtained with the James Webb Space Telescope (JWST) in the mid-infrared. The dayside and nightside spectra (average brightness temperatures of 553 ± 9 and 437 ± 19 K, respectively) each show more than 3σ evidence of absorption features, with H2O as the most likely cause in both. The measured global thermal emission implies that GJ 1214b’s Bond albedo is 0.51 ± 0.06. Comparison between the spectroscopic phase curve data and three-dimensional models of GJ 1214b reveal a planet with a high metallicity atmosphere blanketed by a thick and highly reflective layer of clouds or haze.A spectroscopic thermal phase curve of GJ 1214b obtained with the JWST in the mid-infrared is reported and a planet with a high metallicity atmosphere blanketed by thick and reflective clouds or haze is found. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called ‘metallicity’)1–3, and thus the formation processes of the primary atmospheres of hot gas giants4–6. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets7–9. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification10–12. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme13,14. The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these 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. [ABSTRACT FROM AUTHOR]

Measurements of the atmospheric carbon (C) and oxygen (O) relative to hydrogen (H) in hot Jupiters (relative to their host stars) provide insight into their formation location and subsequent orbital migration1,2. Hot Jupiters that form beyond the major volatile (H2O/CO/CO2) ice lines and subsequently migrate post disk-dissipation are predicted have atmospheric carbon-to-oxygen ratios (C/O) near 1 and subsolar metallicities2, whereas planets that migrate through the disk before dissipation are predicted to be heavily polluted by infalling O-rich icy planetesimals, resulting in C/O < 0.5 and super-solar metallicities1,2. Previous observations of hot Jupiters have been able to provide bounded constraints on either H2O (refs. 3–5) or CO (refs. 6,7), but not both for the same planet, leaving uncertain4 the true elemental C and O inventory and subsequent C/O and metallicity determinations. Here we report spectroscopic observations of a typical transiting hot Jupiter, WASP-77Ab. From these, we determine the atmospheric gas volume mixing ratio constraints on both H2O and CO (9.5 × 10−5–1.5 × 10−4 and 1.2 × 10−4–2.6 × 10−4, respectively). From these bounded constraints, we are able to derive the atmospheric C/H ( 0.35 − 0.10 + 0.17 × solar) and O/H ( 0.32 − 0.08 + 0.12 × solar) abundances and the corresponding atmospheric carbon-to-oxygen ratio (C/O = 0.59 ± 0.08; the solar value is 0.55). The sub-solar (C+O)/H ( 0.33 − 0.09 + 0.13 × solar) is suggestive of a metal-depleted atmosphere relative to what is expected for Jovian-like planets1 while the near solar value of C/O rules out the disk-free migration/C-rich2 atmosphere scenario.The C/O ratio of the transiting hot Jupiter WASP-77Ab is measured here and found to be approximately solar, though the (C+O)/H ratio is subsolar. [ABSTRACT FROM AUTHOR]

The article discusses signs of water have been seen in the atmosphere of a Neptune-sized exoplanet, thus paving the way towards the search for water on smaller Earth-like planets. Topics include atmospheric molecules in the exoplanets, ubiquitous and concealing clouds in the solar system, transmission of starlight, gaseous composition of an exoplanet atmosphere, strength of the water-vapour absorption, use of Hubble Space Telescope, and absorption spectral features

The article focuses on the effect of star evolution, such as becoming a red-giant star, on its close-in planets. It states that Mercury, Venus, and Earth are expected to die a fiery death during the Sun's expansion of forming a red-giant star, wherein the atmosphere of the sun will extend on the orbits of the inner planets of the Solar System. Furthermore, it mentions the study of S. Charpinet and colleagues regarding on two planets orbiting around a star that undergone the red-giant phase.

Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5 μm to 12 μm with the JWST's Mid-Infrared Instrument. The spectra reveal a large day-night temperature contrast (with average brightness temperatures of 1,524 ± 35 K and 863 ± 23 K, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase-curve shape and emission spectra strongly suggest the presence of nightside clouds that become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2 σ upper limit of 1-6 ppm, depending on model assumptions). Our results provide strong evidence that the atmosphere of WASP-43b is shaped by disequilibrium processes and provide new insights into the properties of the planet's nightside clouds. However, the remaining discrepancies between our observations and our predictive atmospheric models emphasize the importance of further exploring the effects of clouds and disequilibrium chemistry in numerical models., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2024.)