Jupiter is currently visible in our night sky as a steady, golden point of light that outshines almost every star around it. To the naked eye, it looks calm and unchanging. But aim a simple pair of binoculars at it, and something remarkable happens. Four tiny pinpricks of light appear alongside the planet. These are Jupiter’s four largest moons, Io, Europa, Ganymede and Callisto. They shift position from night to night, quietly orbiting their giant host in a celestial dance, first noticed by Galileo over 400 years ago.