Dense mega-Earth GJ 523b challenges planetary norms with thin atmosphere

Astronomers have identified GJ 523b, a dense 'mega-Earth' about 2.5 times Earth in size and around 23 times as massive, with a surprisingly thin atmosphere. Discovered by NASA’s TESS and examined with the WIYN telescope and the James Webb Space Telescope, the planet’s high density and lack of a thick gaseous envelope defy simple formation models, leading researchers to speculate that extreme heat or a past planetary collision stripped away much of its atmosphere and to push for a clearer definition of the Mega-Earth category.