DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
Sectional map of our Galaxy, the Milky Way, drawn by William Herschel in 1785 for a paper entitled "On the Construction of the Heavens". He used two (false) assumptions to produce this diagram of the Galaxy; first, that its stars are uniformly distributed, and second, that his telescope was able to see to the very edge. He reasoned that he could infer the Galaxy's shape by comparing the number of stars seen in different directions; the more stars visible, the greater the distance to the edge. The bold asterisks in this diagram are hence in effect a plot of the number of stars visible in a particular direction, these numbers could then be translated into distances.
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