The Week in SpaceJanuary 11-17, 2010
Make That FOUR Moons During the winter of 1609-10, Italian astronomer Galileo Galilei made a series of discoveries that forever changed our understanding of the universe. Using a small telescope that he built, Galileo observed three “stars” that seemed to move in orbits around Jupiter. A week later, he noticed a fourth. These four “Galilean” moons of Jupiter dramatically contradicted the centuries-old notion of an Earth-centered universe by proving that not everything orbits Earth: some things, like these new moons, orbit Jupiter. The first three moons Galileo discovered are called Io, Europa, and Callisto. The fourth, Ganymede, was discovered 400 years ago this week. In this approximately natural color Hubble Space Telescope image from 2007, Ganymede is just about to disappear behind Jupiter. Image credit: NASA, ESA, and E. Karkoschka (University of Arizona) Weekly CalendarJanuary 11-17, 2010Holidays - Sky Events - Space History
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