Jupiter and Three Moons

Firing off a string of action snapshots like a sports photographer at a NASCAR race, NASA's Hubble Space Telescope captured the rare occurrence of three of Jupiter's largest moons racing across the banded face of the gas-giant planet: Europa, Callisto, and Io. These so-called Galilean moons, named after the 17th century scientist Galileo Galilei, who discovered them with a telescope, complete orbits around Jupiter with durations ranging from 2 days to 17 days. They can commonly be seen transiting the face of Jupiter and casting shadows onto its cloud tops. However, seeing three moons transiting the face of Jupiter at the same time is rare, occurring only once or twice a decade.