Clyde Tombaugh discovered Pluto - 84 years after star-spotters first began their hunt for a ninth planet in our solar system, the elusive ‘Planet X’ on 18th February 1930.

The 24-year-old made the groundbreaking discovery at the Lowell Observatory, Arizona, just one week into a task that had mired other researchers for decades. That said, it was later realised that Pluto had been spotted on previous occasions, yet astronomers had mistakenly overlooked its significance.

In this episode, The Retrospectors reveal how the ‘planet’ came to be named by an 11-year-old British girl; explain why it is no longer a planet at all, but has been downgraded to ‘dwarf planet’; and consider Walt Disney’s influence on its place in the public affections…

Further Reading:

‘Clyde Tombaugh: the astronomer who discovered Pluto’ (BBC Sky at Night Magazine, 2020): https://www.skyatnightmagazine.com/space-science/clyde-tombaugh-astronomer-discovered-pluto

‘Obituary: Clyde W. Tombaugh, 90, Discoverer of Pluto’ (The New York Times, 1997): https://www.nytimes.com/1997/01/20/us/clyde-w-tombaugh-90-discoverer-of-pluto.html?smid=nytcore-ios-share&referringSource=articleShare

‘How Clyde Tombaugh Discovered Pluto’ (Smithsonian National Air and Space Museum, 2023): https://www.youtube.com/watch?v=i_UPCOOuNg8

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The Retrospectors are Olly Mann, Rebecca Messina & Arion McNicoll, with Matt Hill.

Theme Music: Pass The Peas. Announcer: Bob Ravelli. Graphic Design: Terry Saunders. Edit Producer: Ollie Peart.

Copyright: Rethink Audio / Olly Mann 2025.

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