Dense Mega-Earth Gliese 523b Defies Planet Formation Theories with Polar Orbit
Astronomers confirm Gliese 523b—a dense meg-eath about 2.55 Earth radii and 23.5 Earth masses (density ~7.8 g/cm3) orbiting the young, ~169‑million‑year‑old star Gliese 523 every 17.75 days on a highly inclined, near-polar orbit (inclination ≥71°). With little or no atmosphere, it challenges standard formation models. The planetary nature was established using NEID radial‑velocity data and TESS transits. Its enigmatic characteristics have scientists exploring scenarios such as atmospheric stripping, warped protoplanetary disks, undetected outer companions, or giant impacts that prevented thick atmosphere formation.