It’s not certain just what led to the ‘naked’ jovian world, but there are two theories. TOI-849b is so close to its star that it completes an orbit in 18 hours, raising the possibility that tidal disruptions or a planetary collision stripped it of gas. Evaporation due to starlight is a possibility, but wouldn’t account for all the lost gas. This could also be a failed gas giant where a gap in the formative dust disc, or a late formation, robbed the planet of gas.
More observations will be necessary to determine just what materials are part of the core. Even so, this is notable simply for showing that these kinds of planets can exist. Like other recent findings, it’s illustrating how complex the cosmos can be.