55 Cancri e
55 Cancri e (55 Cnc e) is a tidally locked super-Earth lava planet orbiting a sun-like star at ~41 light-years. Its extreme orbital proximity (0.7-day period, far closer than Mercury’s 88-day orbit) keeps the dayside surface molten; the planet is tidally locked, producing a permanent hot hemisphere.
Properties
- Radius: ~1.88 R⊕
- Mass: ~8 M⊕
- Orbital period: 0.7 days
- Host star: 55 Cancri A, sun-like (G8V), ~41 ly
- Surface: global magma ocean on the dayside
2026 JWST atmospheric detection
In 2026, ignas-snellen et al. used jwst to observe five eclipse events, detecting — contrary to prior carbon-oxide lava-planet models — a hydrogen- and CO-rich atmosphere with minor CO₂. Variable eclipse depths across the five observations are interpreted as active outgassing or transient clouds driven by outgassing from a low-oxygen-fugacity interior. This secondary-atmosphere composition contrasts with the sulphur-rich atmosphere of sibling lava planet l-98-59-d, demonstrating that interior redox state (oxygen fugacity) governs secondary-atmosphere diversity across the magma-ocean-world class. Underlying paper: arXiv 2606.11866 (submitted to Nature Astronomy).