Annabella Meech

The young star TOI-451 wobbles slightly as three planets circle it. Each wobble is like the tremor of a spiderweb when a tiny spider crawls across it. Astronomers caught this tremor to learn how heavy the planets are. They watched the star for several months using telescopes on Earth. The planets kept passing in front of the star, briefly dimming its light.

A balloon someone forgot to tie off deflates before your eyes. That is roughly how GJ 3090b behaves: its hydrogen-helium envelope is leaking into space at a rate that surprised astronomers. The planet is only twice the size of Earth, yet it is shedding gas as if it wanted to get rid of everything superfluous as fast as possible.