Galileo Galilei spent February of 1610 scrutinizing Jupiter through his 30x magnification telescope. By the end of March, he had announced the discovery of four Galilean moons: Io, Europa, Callisto, and Ganymede. The moons were important both scientifically and philosophically; they proved that the universe was home to a plurality of worlds, and reiterated that Earth was decidedly not the pivot point around which they all revolved.
Advertisement
Just a little over four centuries later, the Hubble Telescope has captured gorgeous images and timelapses of three of the moons transiting in front of Jupiter (Ganymede was a no show).Though the individual transits of these moons are common, triple transits are fairly rare, occurring about once every ten years. (North American skywatchers won't get treated to another one until 2032.)Hubble capitalized on the event by documenting the transits, which lasted for a total of 42 minutes, on the telescope's Wide Field 3 visible light camera. The fact that Galileo himself was hard at work discovering them at around this time of year in 1610 gives the whole thing an extra coat of cool.