Our solar system is home to hundreds of moons, but a select few stand out for their sheer size. These largest satellites are not merely rocks in orbit; they are diverse, geologically active worlds that rival the size of some planets.
Astronomers working with JWST have found a jellyfish galaxy only about 5 billion years after the Big Bang. Jellyfish galaxies are so named because they trail streams of gas that look like jellyfish tentacles. They're created when a galaxy moves rapidly through a cluster, and the intracluster medium (ICM) strips gas from them, stretching it into long streams.

