Scientists studying the planet HIP 67522b with the James Webb Space Telescope (JWST) found that it may be an entirely different planet, with an extensive atmosphere full of water vapor and carbon dioxide.

JWST observations showed that by further analyzing the thickness of the atmosphere, astronomers suggest that HIP 67522b weighs 14 times the mass of Earth despite its Jupiter-like size. That makes it one of the lightest giants ever discovered – and more like a sub-Neptune than Jupiter.

But unfortunately for HIP 67522b, its low mass dooms it to this harsh fate, according to the studies here. Today we see it as a giant, bloated planet, but its close proximity to its star and inability to hold onto its gas tightly means it would lose much of the gas we currently see around it. Its atmosphere is already boiling, and it will probably lose it in the next billion years. Only the shrunken core remains.

This detailed study shows (among many other things) how powerful JWST can be for measuring the masses of young exoplanets.