The search for Pluto began as a triumph of mathematics and ended as one of the strangest coincidences in astronomy. After Neptune was found in the 1840s exactly where Urbain Le Verrier's equations pointed, astronomers became convinced lingering wobbles in Uranus's orbit meant another giant world lay beyond. Percival Lowell poured his fortune into hunting his Planet X, mathematician Elizabeth Williams ran the calculations by hand, and in 1930 a 23-year-old Kansas farm boy named Clyde Tombaugh spotted a moving dot with a blink comparator. It was right where the math said to look, and the math turned out to be completely wrong.

This episode follows Pluto's biography from its naming by 11-year-old Venetia Burney through the decades of shrinking mass estimates, the discovery of Charon in 1978 that revealed Pluto weighs just 0.2 percent of Earth, ...