2025/05/09 by Amy Louca, Yamila Miguel, Louca, Amy +1 · 1 voice
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph.EP
paper · pdf · doi:10.48550/arxiv.2505.06013
openalex publication_date 2025/05/09 · arxiv published 2025/05/09 · arxiv updated 2025/05/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Planet formation impacts exoplanet atmospheres by accreting metals in solid form, leading to atmospheric C/O and S/N ratios that deviate from their host stars. Recent observations indicate differing metal abundances in planetary atmospheres compared to their stellar companions (e.g., Alderson et al. 2022; Bean et al. 2023). However, these observations are biased toward mature planets, raising questions about whether these abundances result from formation or evolved over time. Another way to alter an atmosphere is through the qescape of particles due to thermal heating. This study examines how billions of years of particle escape affect metal abundances. Using an adjusted stellar evolution code incorporating hydrodynamic escape, we model a warm (Teq ≈ 1000 K) super-Neptune-type planet (Mini = 26 M⊕) orbiting a solar-type star. Our results show increased metal-to-hydrogen abundances of ∼50-70x initial enrichment after 10 Gyr. We also see a 0.88x decrease in C/O abundance and a 1.27x increase in S/N abundance, which can affect the interpretation of planet formation parameters. We also simulate the evolving atmosphere using chemical kinetics and radiative transfer codes, finding substantial increases in SO2, CO2, and H2O abundances and a decrease in CH4 abundance. These changes are easily observable in the IR waveband transmission spectrum. Our findings demonstrate that extreme escape of lighter particles significantly influences the evolution of warm Neptunes and complicates the interpretation of their observational data. This highlights the need to consider long-term atmospheric evolution in understanding exoplanet compositions.