2024/10/11 by Yao Tang, Jonathan J. Fortney, Tang, Yao +3 · 5 citations
Engineering · Physics and Astronomy · #Astro and Planetary Science #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Planetary Science and Exploration #Spacecraft and Cryogenic Technologies
paper · pdf · doi:10.48550/arxiv.2410.08577
openalex publication_date 2024/10/11 · openalex created_date 2024/10/16 · openalex updated_date 2026/07/28
We develop a python-based state-of-the-art sub-Neptune evolution model that incorporates both the post-formation boil-off at young ages ≤ 1 Myr and long-lived core-powered mass loss (∼ Gyrs) from interior cooling. We investigate the roles of initial H/He entropy, core luminosity, energy advection, radiative atmospheric structure, and the transition to an XUV-driven mass-loss phase, with an eye on relevant timescales for planetary mass loss and thermal evolution. With particular attention to the re-equilibration process of the H/He envelope, including the energy sources that fuel the hydrodynamic wind, and energy transport timescales, we find boil-off and core-powered escape are primarily driven by stellar bolometric radiation. We further find that both boil-off and core-powered escape are decoupled from the thermal evolution. We show that, with a boil-off phase that accounts for the initial H/He mass fraction and initial entropy, post-boil-off core-powered escape has an insignificant influence on the demographics of small planets, as it is only able to remove at most 0.1% of the H/He mass fraction. Our numerical results are directly compared to previous work on analytical core-powered mass loss modeling for individual evolutionary trajectories and populations of small planets. We examine a number of assumptions made in previous studies that cause significant differences compared to our findings. We find that boil-off, though able to completely strip the gaseous envelope from a highly irradiated (F ≥ 100 F_⊕) planet that has a low-mass core (Mc ≤ 4M_⊕), cannot by itself form a pronounced radius gap as is seen in the observed population.