Year: 2026
Type: article
Abstract: An open question in exoplanet science is whether rocky exoplanets extremely close in to their host stars, “lava worlds,” can retain significant atmospheres. Thermal emission observations via secondary eclipse can be used to determine whether a rocky exoplanet possesses an atmosphere. It is expected that an atmosphere could increase the planet’s albedo and/or redistribute heat away from the dayside, reducing the secondary eclipse depth measured. Recent eclipse observations of lava planets, rocky planets hot enough to have liquid magma surfaces, have suggested the presence of atmospheres. Here, we present a single JWST MIRI/LRS partial secondary eclipse of the lava planet TOI-431b. We measure an eclipse depth of 81 ± 16 ppm, which corresponds to a brightness temperature of 196 7 − 253 + 237 K and a brightness temperature ratio R = 0.81 ± 0.10, being 1.2 σ higher than the value reported by Spitzer. The observed brightness temperature ratio is 1.8 σ below that of a zero-albedo, zero heat redistribution bare rock ( R = 1). Given that magma pools are expected to have low albedos, we find that our results are best explained by the presence of an atmosphere. Future work to measure the exact composition of TOI-431b’s atmosphere and improve models of lava planet atmospheres would better constrain the nature and evolution of lava planets.
Source: The Astronomical Journal
Institutions: University of Maryland, College Park, University of Chicago, Consejo Superior de Investigaciones Científicas, Instituto de Astrofísica de Andalucía, University of Birmingham, Carnegie Institution for Science, Space Telescope Science Institute, Peking University, The University of Texas at Austin, Universidad de La Laguna, Instituto de Astrofísica de Canarias
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Aeronautics and Space Administration, Space Telescope Science Institute, UK Research and Innovation, European Commission, National Natural Science Foundation of China, Ministerio de Ciencia e Innovación, Graduate School, University of Maryland, Science and Technology Facilities Council, European Regional Development Fund, Agencia Estatal de Investigación
Awards: G103270039, G1129048233, G1175115578, G121809054, G1381791653, G1426358987, G1610079134, G1622782223, G1855990336, G210041235, G2262748287, G2262804166, G2309174360, G256731684, G2601397997, G2650114919, G2660406951, G279363373, G300979063, G34346518, G3452655474, G3480869486, G3518538256, G3681454997, G3696727022, G3817602061, G387506447, G4042783231, G410571670, G425668148, G430777504, G451917667, G4526231891, G463062595, G5080475149, G5180915604, G5195188938, G5421974903, G5539308778, G5560776957, G5662792045, G5881647929, G5894067328, G5967599077, G6115201310, G6687049611, G6877667232, G7084143925, G7434936867, G7518687652, G897484643, G929308097, G99296377
OpenAlex ID: W7208705829