Overview
- Webb’s NIRSpec measured the planet’s dayside near 1,800°C, far below the ~2,700°C expected for bare rock, signaling a substantial gaseous envelope.
- The results, published in The Astrophysical Journal Letters, come from GO-3860 observations that continuously monitored the system for over 37 hours across nearly four orbits.
- TOI-561 b is about 1.4 Earth radii, completes an orbit in under 11 hours, and is likely tidally locked with a permanent dayside and nightside.
- The atmosphere helps account for the planet’s unusually low bulk density and its context around an old, iron-poor thick-disk star suggests formation in a different chemical environment.
- Researchers propose a magma–atmosphere equilibrium that replenishes and reabsorbs volatiles, and they are now analyzing the full dataset to map temperatures and identify key gases.