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Try to imagine what must have gone through Galileo Galilei's mind one January evening in 1610 when he first realized that the four points of light he saw through his new telescope were, in fact, worlds circling Jupiter. The thrill of discovery would have been magnified by the simultaneous realization that an unshakable truth that all worlds revolved around the Earth had just collapsed. Although viewing these same moons might not shake up your own worldview, you can at least relive some of Galileo’s excitement by discovering them for yourself with nothing more than binoculars or a small telescope.
Knowing in advance where the moons will be makes finding and identifying them much easier, but keep in mind that each one becomes temporarily invisible when passing in front of or behind Jupiter, or when passing through its shadow. Don’t be surprised if you see only two or three moons most of the time. The easiest to catch are Ganymede and Callisto. They orbit farthest from their host and spend days at a time beyond Jupiter’s glare. By contrast, Io and Europa never venture far from the planet's disk.