On January 7, 1610, the Italian astronomer Galileo discovered three of Jupiter's moons: Callisto, Europa and Io.
When he looked at Jupiter through his telescope, he saw what he thought were three tiny stars in the background, and he sketched their locations. The next day, he looked again and saw the three stars were not where he thought they'd be. Instead of being "fixed" in the background like other stars, they moved along with the planet, and Galileo realized that Jupiter had moons. Besides Earth's moon, these were the first natural satellites anyone had ever seen in the solar system.
When he looked at Jupiter through his telescope, he saw what he thought were three tiny stars in the background, and he sketched their locations. The next day, he looked again and saw the three stars were not where he thought they'd be. Instead of being "fixed" in the background like other stars, they moved along with the planet, and Galileo realized that Jupiter had moons. Besides Earth's moon, these were the first natural satellites anyone had ever seen in the solar system.
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00:00 On this day in space.
00:04 On January 7th, 1610, the Italian astronomer Galileo discovered
00:08 three of Jupiter's moons, Callisto, Europa, and Io.
00:12 When he looked at Jupiter through his telescope, he saw what he thought were three tiny stars in the
00:16 background, and he sketched their locations. The next day, he looked again
00:20 and saw that the three stars were not where he thought they'd be. Instead of being fixed
00:24 in the background like other stars, they moved along with the planet, and Galileo realized
00:28 that Jupiter had moons. Besides Earth's moon, these were the first natural
00:32 satellites anyone had ever seen in the solar system. And that's what happened
00:36 on this day in space.
00:40 (music)