Clyde Tombaugh hesitated, his knuckles at his boss’ door, his heart knocking against his chest. He had reason to be nervous. He was about to expand the solar system. He, an uneducated farm boy, was going to tell an astronomer with a name like a comic book villain – Dr. Vesto Slipher – that he had found Planet X.
The discovery of Planet X, aka Pluto, is a story of the underdog: a farmer, a little girl and the little planet that could (and then couldn’t). It is a story of obsession. And it’s a story of mistakes.
If those mistakes hadn’t been made, 2015 would not have been declared The Year of Pluto. NASA’s New Horizons spacecraft would not be making humanity’s first close encounter with the dwarf planet this July 14. And the place where it all began, Flagstaff’s Lowell Observatory, wouldn’t even exist.
In scientific circles, observatory founder Percival Lowell is a cautionary tale. The wealthy Bostonian spent the 1880s traveling through Asia, serving as foreign secretary in Korea and writing about his exotic experiences. But the Far East wasn’t his obsession. It wasn’t far enough away.
Lowell had read astronomer Giovanni Schiaparelli’s description of lines on the surface of Mars he called canali. The word, which means “channels” in Italian, got mistranslated in English as “canals.” To paraphrase Mark Twain, the difference between the right word and the almost-right word is the difference between lightning and a lightning-bug.
“Channels” implies natural phenomena. “Canals” implies Martian gondoliers.
Lowell became convinced the canals were a hydraulic engineering system that delivered water from the poles to a civilization dying of thirst. He popularized the idea so convincingly that canals later ran through the plots of Ray Bradbury’s The Martian Chronicles and Edgar Rice Burroughs’ A Princess of Mars.
Lowell had to investigate the waterways. So in 1894 he founded the first observatory built in a remote, high-altitude location to take advantage of dark skies. (In 2001, thanks to the observatory, Flagstaff became the world’s first International Dark Sky City.)
There was only one problem. Those lines crisscrossing Mars? They don’t exist. They’re an optical illusion created by the eye’s tendency to connect dots and the imagination’s desire for cosmic companions. But Lowell maintained their existence despite scientists’ mounting skepticism.
Fortunately, a new obsession gripped him. Astronomers were puzzling over Uranus’ and Neptune’s physics-defying orbits. Lowell hypothesized a more distant planet’s gravity was tugging at the ice giants. He calculated where “Planet X” might be and spent the last eight years of his life looking for it – in vain.
Only after Voyager 2’s 1989 flyby did astronomers discover there were no orbital irregularities; they’d overestimated Neptune’s mass. “The end result was that there was no reason ever to look for Pluto,” Lowell Observatory educator Jim Cole says. “If they had estimated the mass right, the search would have stopped there.”
Fortunately for one farm boy, science did not yet know its mistake.
In 1922, high schooler Clyde Tombaugh’s family moved from Illinois to a farm in Kansas. Soon after, a hailstorm destroyed their crops and Tombaugh’s hopes of affording college.
But he self-educated. After memorizing every country on Earth, he became intrigued by other planets’ geographies. He built telescopes from farm machinery. At 22, he made drawings of Mars and Jupiter and sent them to Lowell Observatory. Director Vesto Slipher was so impressed he invited Tombaugh to work at Lowell – as a groundskeeper.
Arriving at the frontier observatory, “I was rather unnerved by it all,” Tombaugh wrote in a scientific journal. But he couldn’t afford a train ticket back. Slipher, too, was under financial pressure. After Lowell’s death, his widow, the ironically named Constance, spent a decade trying to take the money earmarked for the observatory’s operating costs. Slipher used most of the remaining funds to purchase an expensive telescope to find Planet X. He needed results, fast. So he gave the task to Tombaugh.
Every night, Tombaugh pointed the telescope at specific coordinates and used a rope to heave open the dome’s shutters. In winter, he’d first climb to the dome and slip across the icy, sloped roof to knock snow off the shutters. Back down, he put a photographic glass plate in the astrograph and turned on a motor that swivels the telescope to compensate for the Earth’s rotation. Then he waited for the hour-long exposure, checking the telescope’s aim every five minutes. In the solitary darkness, the only sounds were his teeth chattering and the occasional BOOM of a glass plate shattering in the freezing cold. Sometimes he did four one-hour exposures.
Afterward, he developed the plates in his apartment, snatched a few hours of sleep, then started his groundskeeper duties. In between shoveling snow and coal, he shoehorned in several hours to examine the plates. He put them in a “blink comparator,” scrutinizing tiny sections – back and forth – looking for a moving dot among up to 400,000 stars.
“I was a perfectionist,” Tombaugh wrote in his book, Out of the Darkness. “When I planted the kafir corn and milo maize, the rows across the field had to be straight as an arrow or I was unhappy. Later, every planet-suspect, no matter how faint, had to be checked out [by inspecting] a third plate – either yes or no, not maybe.”
In February 1930, after 10 months of searching, Tombaugh found the dot, becoming the third person in recorded history to discover a planet. The world’s most prestigious universities offered him scholarships. But he turned them down to stay at Lowell and earn his master’s degree in astronomy via correspondence courses with the University of Kansas.
Meanwhile, telegrams flooded in suggesting names for Planet X. Appropriately, the winner came from an underdog: Venetia Burney, an 11-year-old girl from Oxford, England. She thought Pluto – the Roman god of the underworld – would be a good name for a darkness-dweller. Tombaugh liked it because the first two letters recall the man who started it all: Percival Lowell.
Pluto was still a planet when Tombaugh died in 1997 – and when New Horizons launched in January 2006. Seven months later, it was controversially demoted to “dwarf planet.” But by then, the spacecraft was already speeding toward Pluto at 36,000 mph, carrying the ashes of Clyde Tombaugh.
Lowell Observatory’s exhibit celebrating the 85th anniversary of Pluto’s discovery runs through the end of 2015.
1400 W. Mars Hill Rd., Flagstaff, 928-774-3358, lowell.edu
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