Researchers at the University of Wisconsin–Madison have identified an exoplanet, GJ 523b, that defies conventional models. About 2.5 times wider than Earth, it packs roughly 23 times our planet’s mass — resulting in an unusually high density. What’s striking is that despite its massive size, it appears to have very little gaseous atmosphere. Scientists now propose classifying such worlds as «mega-Earths» — a category for exceptionally dense, predominantly rocky planets. Two leading hypotheses: either the planet once had a thick atmosphere that was later stripped away due to proximity to its star, or it formed from a massive collision between two rocky planets, which blasted off much of the gaseous envelope.
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