Broke Boy From Kansas Finds Planet X  |  This Week In Space History

by michael shinabery

Editor’s note: This is part one of a two-part story.

Secrecy prevented Clyde Tombaugh from even telling his parents he’d made one of the early 20th century’s biggest scientific discoveries. They only heard “when the editor of their county newspaper called,” Mark Littman wrote in “Planets Beyond: Discovering the Outer Solar System” (Wiley Science Editions/1988).

On Feb. 18, 1930, Tombaugh photographed Planet X, after more than a year of work at the Lowell Observatory, Flagstaff, Arizona. Percival Lowell, who in 1894 opened the observatory, first postulated in the late 1800s about a ninth planet in the solar system, even though “many astronomers were pessimistic,” Tombaugh said in the March 1960 Sky and Telescope.

Tombaugh was born in Illinois, but when he was 16 his family rented a farm in Burdett, Kan. They weren’t very successful at living off the land. In high school, Tombaugh even dropped out a year to work the farm. After graduation he yearned to go to college, but there was just no money.

His father and uncle, however, nurtured his interest in astronomy, and at age 20 Tombaugh built his first telescope. Littman said the tube was made from pine boards, and the mount from discarded farm machinery; the mirror he ground from a ship’s porthole glass. Tombaugh made successively larger scopes, scrounging parts and even using a cream separator, a May 12, 1980 “People” article cited. He was 22 when he drew “meticulous sketches” of Jupiter, Saturn and Mars. Wanting a professional appraisal, in 1929 he mailed them to the Lowell Observatory.

“Interest in the planet Mars first brought me to Lowell,” Tombaugh wrote in Sky and Telescope.

The director, Vesto Slipher, offered him a job. According to Tombaugh, “Slipher’s invitation also mentioned photographic observing, and (he) asked, ‘Are you in good physical health?’ ”

Tombaugh had enough cash for a seat on the 28-hour train ride. Littman wrote he “didn’t have enough money to sleep in a Pullman berth,” and if he failed he had no funds “to return home.” On Jan. 15, 1929, Tombaugh stepped off the train, so broke he couldn’t even rent a room. So, he slept in the observatory.

“Photography obviously provided the only efficient search technique,” Tombaugh wrote in Sky and Telescope. “But at the beginning of the 20th century, photographic emulsions were less sensitive and less reliable than they are today.”

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The observatory first used photography in an “intensive search from 1905 to 1907,” with no success, he said. Exacerbating the low-quality of film was “Pluto itself was many degrees from the ecliptic, and thus outside the belt covered by the plates.”

In 1914, the “hunt” resumed for two years, until “Lowell’s untimely death.” Ironically, inspection of the plates years later revealed they “actually contained weak images of the planet.” Three years later, “in 1919 at Harvard Observatory, W. H. Pickering concluded a theoretical study of the motion of Neptune, from which he also predicted the existence of a planet beyond it.”

Another decade would pass before the search earnestly resumed. Tombaugh described the tedious technical process in Sky and Telescope. An undated document in the New Mexico Museum of Space History Archives said he made photographs on 8-by-10 glass plates using “a technique whereby he could take two pictures of the same small part (of the sky) on two different days. Each of them would have from 50,000 to 400,000 stars on it. If the two plates were focused on a given spot on a screen in rapid alternation, none of the stars should seem to move. If one of the ‘stars’ were really a planet, however, one that had moved against the starry background during the interval between the photographs, it would shift position, and as the photos are alternately thrown upon the screen, the one star would seem to dart back and forth.”

Rapidly comparing the two plates was called “blinking” on a device known as the “Blink Comparator.” The document stated: “Some of the plates of the Milky Way were so crammed full of stars that three to four weeks of intensive work were required to blink a single pair of plates.” On Feb.18, 1930, after 7,000 hours of photographing and comparing, “Tombaugh found a ‘star’ in the constellation Gemini that flickered.”

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“I suddenly spied a 15th-magnitude object popping in and out of the background. Just 3-1/2 millimeters away another 15th-magnitude image was doing the same thing,” Tombaugh wrote. “ ‘That’s it!’ I exclaimed to myself.”

Until the discovery could be confirmed, Slipher ordered secrecy.

“Tombaugh didn’t even tell his parents,” Littman said.

“It was decided to announce the discovery on March 13, 1930, which was the 75th anniversary of Percival Lowell’s birth, and the date of Uranus’ discovery 149 years earlier,” Tombaugh wrote. “The next day the news spread out over the world. Soon newspaper and magazine reporters arrived in Flagstaff and swarmed over the observatory on Mars Hill. Letters and telegrams poured in, containing congratulations and suggesting names for the new planet. Around the observatory all other work was disrupted.”

Tombaugh was now famous, and college was a reality. At 26, he entered the University of Kansas on a scholarship to study astronomy. The department head promptly refused him entrance into the beginning class, pronouncing, (Littman quoted): “For a planet discoverer to enroll in a course of introductory astronomy is unthinkable.”

Michael Shinabery is an education specialist and Humanities Scholar at the New Mexico Museum of Space History.

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