Search

Detection of molecules using infrared spectroscopy probes the conditions and compositions of exoplanet atmospheres. Water ([H.sub.2]O), methane (C[H.sub.4]), carbon dioxide (C[O.sub.2]), and carbon monoxide (CO) have been detected (1-5) in two hot Jupiters. These previous results relied on space-based telescopes that do not provide spectroscopic capability in the 2.4-5.2 µm spectral region. Here we report ground-based observations of the dayside emission spectrum for HD 189733b between 2.0-2.4 µm and 3.1-4.1 µm, where we find a bright emission feature. Where overlap with space-based instruments exists, our results are in excellent agreement with previous measurements (2,6). A feature at ~3.25 um is unexpected and difficult to explain with models that assume local thermodynamic equilibrium (LTE) conditions at the 1 bar to 1 x [10.sup.-6] bar pressures typically sampled by infrared measurements. The most likely explanation for this feature is that it arises from non-LTE emission from C[H.sub.4], similar to what is seen in the atmospheres of planets in our own Solar System (7-9). These results suggest that non-LTE effects may need to be considered when interpreting measurements of strongly irradiated exoplanets., Spectroscopic detection of molecules in exoplanet atmospheres is a relatively recent development. High-precision spectroscopy data in combination with spectral retrieval techniques enables the determination of the atmospheric temperature profile and [...]

WASP-107b is a warm (approximately 740 K) transiting planet with a Neptune-like mass of roughly 30.5 M ⊕ and Jupiter-like radius of about 0.94 R J (refs.  1,2 ), whose extended atmosphere is eroding 3 . Previous observations showed evidence for water vapour and a thick, high-altitude condensate layer in the atmosphere of WASP-107b (refs.  4,5 ). Recently, photochemically produced sulfur dioxide (SO 2 ) was detected in the atmosphere of a hot (about 1,200 K) Saturn-mass planet from transmission spectroscopy near 4.05 μm (refs.  6,7 ), but for temperatures below about 1,000 K, sulfur is predicted to preferably form sulfur allotropes instead of SO 2 (refs.  8-10 ). Here we report the 9σ detection of two fundamental vibration bands of SO 2 , at 7.35 μm and 8.69 μm, in the transmission spectrum of WASP-107b using the Mid-Infrared Instrument (MIRI) of JWST. This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from about 1,200 K down to about 740 K. Furthermore, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (around 7σ) over simpler cloud set-ups. Furthermore, water is detected (around 12σ) but methane is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Brown dwarfs serve as ideal laboratories for studying the atmospheres of giant exoplanets on wide orbits, as the governing physical and chemical processes within them are nearly identical 1,2 . Understanding the formation of gas-giant planets is challenging, often involving the endeavour to link atmospheric abundance ratios, such as the carbon-to-oxygen (C/O) ratio, to formation scenarios 3 . However, the complexity of planet formation requires further tracers, as the unambiguous interpretation of the measured C/O ratio is fraught with complexity 4 . Isotope ratios, such as deuterium to hydrogen and 14 N/ 15 N, offer a promising avenue to gain further insight into this formation process, mirroring their use within the Solar System 5-7 . For exoplanets, only a handful of constraints on 12 C/ 13 C exist, pointing to the accretion of 13 C-rich ice from beyond the CO iceline of the disks 8,9 . Here we report on the mid-infrared detection of the 14 NH 3 and 15 NH 3 isotopologues in the atmosphere of a cool brown dwarf with an effective temperature of 380 K in a spectrum taken with the Mid-Infrared Instrument (MIRI) of JWST. As expected, our results reveal a 14 N/ 15 N value consistent with star-like formation by gravitational collapse, demonstrating that this ratio can be accurately constrained. Because young stars and their planets should be more strongly enriched in the 15 N isotope 10 , we expect that 15 NH 3 will be detectable in several cold, wide-separation exoplanets., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)