Sixteen small worlds just broke the neat rules.

Mini Neptunes should have been the easy middle children of exoplanets, bigger than Earth, smaller than Neptune, predictable in bulk and behavior. Then a set of sixteen worlds started misbehaving. Their spectra refused to line up, their densities hinted at hidden interiors, and their atmospheres looked less like thick blankets and more like scraps. Astronomers using new space based tools can now see what older telescopes blurred. The unsettling part is what these patterns imply about planet birth across space.



