Dense Mega-Earth GJ 523b Defies Conventional Planet Formation

Astronomers confirm GJ 523b, a rock-dominated mega-Earth about 23 Earth masses and 2.5 Earth radii in a 170-million-year-old system, orbiting its star every 17.75 days. Its extreme density and thin atmosphere challenge standard models that would normally push such a core to become a gas giant, prompting theories like atmospheric stripping from stellar heat or a head-on collision of rocky protoplanets. This discovery provides a rare glimpse into how ultra-dense worlds form and evolve.