James Webb Space Telescope finds water in super-hot exoplanet's atmosphere

Nov 19, 2021
At 2200°C, 3% of water molecules are disassociated.
At 3000°C, 50% are.
This planet is about 40% disassociated.
Plenty of water molecules to show up in the spectrometer.
This is a hot exoplanet :) ref - A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b, https://www.nature.com/articles/s41586-023-06230-1, 31-May-2023. "Abstract 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 and Spitzer Space Telescopes1–3. 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. .."

WASP-18 b was difficult to measure in past reports on the atmosphere, now better with JWST.

Exploring the Ability of HST WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres Through a Homogeneous Transmission Survey of 70 Gaseous Planets, https://arxiv.org/abs/2211.00649

My observation. 61-page PDF report attached. The report studies atmosphers of 70 gaseous exoplanets. WASP-18 b is referenced, http://exoplanet.eu/catalog/wasp-18_b/ From the paper, "5. DISCUSSION AND CONCLUSIONS The Hubble Space Telescope has been at the forefront of exoplanet atmospheric characterisation over the last two decades. While many different instruments on this facility have been used, WFC3 has perhaps been the mostly widely utilised due to its sensitivity to water. In this work we have presented a population study of atmospheres, each studied with the WFC3 G141 grism as the planet transits its host star. Of the 70 planets studied, we found strong evidence (>3 sigma) for atmospheric features on 37 of them, with some evidence (2-3 sigma) for spectral modulation on an additional 14 planets. We note that for several planets (e.g. WASP-18 b), the derived spectrum has error bars that are several scale heights in size, meaning no atmospheric constraints could be expected..."

JWST seems to do better :)
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