Hot sub-Neptune Archives

Envelope composition in the H–He–C–N–O–Si chemical system of TOI-421b (𝑅MEB = 1.65𝑅⊕, 𝑅𝑃 = 2.64𝑅⊕, 𝑀𝑃 = 6.7𝑀⊕, 𝑇MEB = 3000 K) as a function of H mass fraction. Elemental budgets, reactions, gas solubility laws, and real gas equations are described in Sect. 2. MEB partial pressures of the considered gases for (a) 1× solar metallicity and 100% mantle melt (IW–6.2 to IW–5.7), (b) 100× solar metallicity and 100% mantle melt (IW–5.5 to IW–5.2), (c) 1× solar metallicity and 1% mantle melt (IW–3.4 to IW–3.1), and (d) 100× solar metallicity and 1% mantle melt (IW–2.3 to IW–1.6). Full range of MEB partial pressures is shown in Fig. A2. The corresponding partitioning of volatile elements in magma and real gas fugacity coefficients are given in Fig. B1 and Fig. B2, respectively. -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Imaging & Spectroscopy, Lava / magma ocean / Volcanic Worlds, Press Release

Silane-Methane Competition in Sub-Neptune Atmospheres As A Diagnostic Of Metallicity And Magma Oceans

by Keith CowingSeptember 1, 2025September 1, 2025

The James Webb Space Telescope is characterising the atmospheres of sub-Neptunes. The presence of magma oceans on sub-Neptunes is expected to strongly alter the chemistry of their envelopes (100 bar-100 […]

Astrochemistry, Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Hot sub-Neptune Exoplanet TOI-421 b NIRISS/NIRSpec Transmission Spectrum

by Keith CowingMay 6, 2025

This is a transmission spectrum captured by the NASA/ESA/CSA James Webb Space Telescope that reveals the presence of water (H2O) and the possible presence of sulfur dioxide (SO2) and carbon […]