2026/07/07 by Viviane Kuss, Robin Wordsworth, Collin Cherubim +1
Physics and Astronomy · #astro-ph.EP
paper · pdf · doi:10.3847/2041-8213/ae8dc5
arxiv created 2026/07/07 · arxiv updated 2026/08/06
We present radiative-convective modeling of rocky exoplanets with He-dominated atmospheres and low envelope mass fractions. Helium has a steeper adiabatic temperature profile than N2 and H2 as it has fewer degrees of freedom. Line broadening differences are small, collision-induced absorption (CIA) is not important in He-dominated atmospheres, and Rayleigh scattering by He is weak. The combined impact of these effects is that He-dominated atmospheres provide more warming than N2-dominated atmospheres but less than H2-dominated atmospheres, for the same surface pressure. For surface pressures in the range 1-20 bar, the habitable zone for rocky planets around M dwarfs with He-dominated atmospheres is narrower than for H2-dominated atmospheres. Nonetheless, due to their large scale height compared to N2 or CO2-dominated atmospheres, temperate He-dominated atmospheres are favorable targets for characterization via transit spectroscopy with JWST.