Jupiter is the most massive planet in our solar system, and in composition it resembles a small star. In fact, if Jupiter had been between fifty and one hundred times more massive, it would have become a star rather than a planet. On January 7, 1610, while skygazing from his garden in Padua, Italy, astronomer Galileo Galilei was surprised to see four small “stars” near Jupiter. He had discovered Jupiter’s four largest moons, now called Io, Europa, Ganymede, and Callisto. In 2003 astronomers discovered 21 new moons orbiting the giant planet. Jupiter now officially has 67 moons. Jupiter has stripes that are dark belts and light zones created by strong east-west winds in Jupiter’s upper atmosphere. Within these belts and zones are storm systems that have raged for years. The southern hemisphere’s Great Red Spot has existed for at least 100 years, and perhaps longer, as Galileo reported seeing a similar feature nearly 400 years ago. Three Earths could fit across the Great Red Spot. Jupiter’s core is probably not solid but a dense, hot liquid with a consistency like thick soup.