Imagine a rocky world where the surface is a churning ocean of lava, heated not by volcanic forces but by the searing proximity of its star. Astronomers believe such a planet exists, and NASA's James Webb Space Telescope has now peered into its atmosphere.
The target is 55 Cancri e (55 Cnc e), a super-Earth about 41 light-years from Earth. It measures roughly 1.88 times Earth's radius and about 8 times Earth's mass, yet circles its Sun-like star in only about 0.7 days — for comparison, Mercury takes 88 days to orbit our Sun. Because it sits so close, scientists believe its surface stays hot enough to remain molten.
Findings submitted for publication in Nature Astronomy could sharpen our understanding of how lava exoplanets form and evolve. A centerpiece result: Webb detected a hydrogen-rich atmosphere around the planet. That is notable because such a close-in world experiences intense stellar radiation that might be expected to strip away light gases — yet a substantial atmosphere appears to survive.
The discovery helps astronomers test competing models of these extreme planets. Some theories held that 55 Cnc e had lost any atmosphere long ago; the hydrogen-rich envelope suggests instead that it may retain or continuously replenish gases, possibly vented from the molten interior. Either way, the planet is a natural laboratory for studying rocky worlds under conditions nothing on Earth experiences.
Knowledge takeaway: Webb observed the super-Earth 55 Cancri e — a molten "lava world" 41 light-years away that orbits in 0.7 days — and detected a hydrogen-rich atmosphere, challenging assumptions that close-in rocky planets lose their atmospheres and offering a testbed for how extreme rocky worlds form and survive.