GJ 367b is an ultra-dense “super-Mercury” discovered in 2021 by TESS. It’s about 0.7 times Earth’s size but mostly iron, orbiting a red dwarf every 7.7 hours with molten dayside lava.
Stripped by radiation, it lost its outer layers—leaving a bare metal core with no atmosphere or life.
This iron cannonball planet teaches us how close-in worlds can be cooked down to their bones.