If you were asked to name the greatest visual observer of all time, whom would you choose? There are many worthy candidates, but my vote would have to go to the 18th-century astronomer William Herschel. He had quite a track record, including the discovery of the planet Uranus as well as thousands of deep-sky objects. That’s a pretty good run.
Herschel did more than just look at the sky, however. He also tried to understand what he was looking at. Based on his studies of how stars appear distributed along the hazy band of the Milky Way, Herschel concluded that the Milky Way is shaped like a flattened disk. We know today that he was exactly right.
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