PLUTO + Percival Lowell
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IMO, the most important thing about Pluto isn't its "discovery" in 1930.
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In truth, I'm not much interested in whether Pluto is or isn't labeled or classified as a "planet"
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What does fascinate me is Percival Lowell. In 1914, this American polymath predicted that there must be an object in the location where Pluto was eventually found. He used mathematical calculations to "guess" the existence of something that was not otherwise observable using the technology of the early 20th century. -- see "February 18, 1930" https://www.history.com/this-day-in-history/pluto-discovered
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One sentence captures my imagination in the 1930 news story which reported the first photographic evidence of a previously unknown object in space. -- see "Ninth Planet is Found Far from Neptune" (AP). Hartford Courant. March 14, 1930. https://www.courant.com/courant-250/moments-in-history/hc-march-13-1930-pluto-discovered-20140305-htmlstory.html
"All observations indicate
the object to be the one
Lowell saw mathematically."
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I'm fascinated by the phrase "saw mathematically."
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Today Pluto is no longer considered a "planet;" however, the search for a ninth solar system planet is ongoing -- see "There’s probably another planet in our solar system," MIT Technology Review. March 5, 2019. https://www.technologyreview.com/s/613060/theres-probably-another-planet-in-our-solar-system/
@chikara The idea it should be there was from observations of small perturbations of the orbits of the nearest, much larger planets.
Very intricate work, as it required sharp observations and data collection, plus the analysis later.