Overview
- A Nature Astronomy study details four sub-Neptunes orbiting a roughly 210‑million‑year‑old K‑dwarf, captured in a rare transitional phase.
- The planets sit near, but not in, mean‑motion resonances, pointing to a once tighter orbital chain that is now slowly spreading.
- Despite similar rocky core masses, the innermost world is stripped of hydrogen‑helium while the outer three retain thin envelopes of about 1%, 5%, and 5% by mass.
- Researchers combined NASA TESS photometry with ground‑based transit‑timing and radial‑velocity data to pin down sizes, masses, and orbits.
- Computer simulations reproduce the observed architecture, tie resonance breaking to mass loss, and place the bulk of atmospheric escape within the first ~100 million years, with authors now extending the approach to other young systems.