Title: An Adolescent and Near-Resonant Planetary System near the End of Photoevaporation

Speaker: Mutian Wang（Nanjing University）

Time: 15:00pm, April 2, 2026

Location: 3-402, PMO Xianlin Campus

Abstract: Young exoplanets provide vital insights into the early dynamical evolution of planetary systems. Many multi-planet systems younger than 100 Myr exhibit mean-motion resonances, but the resonant structures dissolve on timescale of 0.1-1 Gyr timescale, mirroring the Nice model proposed for the Solar System. In this talk, I will report detailed characterization of the ~200-Myr-old TOI-2076 in a near-resonant system, which contains four sub-Neptune planets. We demonstrate that its planets are near to but not locked in mean-motion resonances, making the system dynamically fragile. The four planets have comparable core masses but display a monotonic increase in hydrogen and helium (H/He) envelope mass fractions (from stripped to 1%, 5% and 5%) with decreasing stellar insolation. This trend is consistent with atmospheric mass loss due to photoevaporation. It remains an open question whether the atmospheric loss and the near-resonance have causal links to each other. Our finding provides direct observational evidence that the dynamical and atmospheric reshaping of compact planetary systems begins early and offers an empirical anchor for models of their long-term evolution.