More than a one-hit wonder. Falk, Dan Astronomy. Feb2006, Vol. 34 Issue 2, p40-45 Famous for discovering Pluto, Clyde Tombaugh reached far beyond the planets Clyde Tombaugh's life instantly changed when he discovered Pluto in 1930. Just 24 years old, and with only a high-school diploma, Tombaugh spotted the missing "Planet X." Shortly thereafter, he was awarded a scholarship for his scientific work and returned to school to earn bachelor's and master's degrees in astronomy. Now, 100 years after his birth, both amateur and professional astronomers celebrate this astronomy great. The day he discovered Pluto began like any other during the previous few months. Tombaugh had not been able to observe the night before because of the Moon's glare. So on February 18, 1930, he "blinked" two photographic plates from January 23 and 29. He would work for a half hour, then rest his eyes and brain for the same time, and return to blinking. The task required intense concentration. And at about 4 o'clock in the afternoon on a cold, wintry day in Flagstaff, Arizona, he found it. For 45 minutes, he checked his plates and examined another from January 21. Once Tombaugh was 100-percent positive he had found it, he reported the news to his boss. Twenty- five years of astronomers' searching was over. Finding a path Clyde William Tombaugh (1906-1997) was born in Streator, Illinois, and moved to Kansas at the age of 16 when his parents began farming in the small town of Burdett. Tombaugh would have been the quintessential American farm boy were it not for his fascination -- one might say, obsession -- with astronomy. At the age of 14, he had his first look through a telescope -- a 2 5/16-inch refractor shared by his father and an uncle. He was so interested in the night sky that, in preparing for an evening of stargazing, he once stayed in a closet for an hour to reach the proper level of dark adaption. In the following years, he learned how to grind and polish mirrors; at the age of 21, Tombaugh began building a 9-inch Newtonian reflector. One year later, the telescope was complete, and he was busy scrutinizing the planets. Tombaugh sent drawings he had made of the planets using his homebuilt telescope to the Lowell Observatory in Flagstaff, Arizona. After a few weeks of correspondence, the observatory's director, Vesto Slipher, hired Tombaugh to head one of Lowell's most urgent projects: a photographic search for a new planet believed to lurk in the solar system's outer reaches, beyond Neptune. Things could have happened quite differently. At about the same time Lowell Observatory invited Tombaugh to join its project, he received a job offer from a telescope manufacturer in Wichita, Kansas. Years later, in conversation with his biographer and friend, astronomer David Levy, he recalled his choice: "I went west instead of east. It makes me shudder how my life hung in the balance at that time. If I had gone to Wichita, I would have been an obscure telescope-maker and no one would have heard of me." But in 1929, with no college education, Tombaugh headed west and took up his new post at Lowell. The eighth planet, Neptune, had been discovered in 1846 because of its gravitational influence on Uranus. Yet Neptune, by itself, did not exert enough of a tug to explain Uranus' motion fully. And so, for decades, astronomers had speculated about the existence of a ninth planet -- the infamous "Planet X." Patience is a virtue The machine Tombaugh would come to know intimately during the next 14 years was a 13-inch telescope capable of revealing objects as faint as magnitude 17.5. (This telescope, then called the Lawrence Lowell Telescope, is now named in honor of Tombaugh's discovery as the Pluto Telescope.) The search would involve much more than just peering through this device. After all, the ninth planet -- if it existed -- would be a point of light no different from the thousands of faint stars populating every square degree of the sky. The key to discovering the missing planet would rest in its motion against the backdrop of fixed stars. That motion is too small to detect in "real time" by a human observer -- but photographs taken weeks apart would record an object's slight shift in position. Tombaugh's task, then, was twofold: He had to photograph the night sky using the 13-inch scope and then compare the images on the resulting photographic plates, two at a time. The machine specially devised for this second task is called a blink comparator. It allows the viewer to alternate quickly between two plates, each of them aligned so the star images remain in the same apparent position. The task was, to say the least, daunting. Each plate -- even those from star fields far from the Milky Way -- had at least 40,000 star images. Even the least-heavily populated photos required 3 days of solid "blinking." The plates from Sagittarius, near the heart of our galaxy, recorded more than a million stars. Each pair of images from these rich fields could take a month to study. In all, Tombaugh spent roughly 7,000 hours during a period of 14 years blinking plates as part of a survey that covered two-thirds of the sky. If anyone can sympathize with Tombaugh's quest, it is Brian Skiff, a research assistant who has worked at Lowell since the early 1980s. Skiff spent many years using the 13-inch scope and a machine that projected the images onto small square plates (to lessen eye strain) in an extensive asteroid search. In all, he has probably logged as many hours exposing and blinking plates as Tombaugh did. "There's a certain amount of Zen-like patience involved," Skiff concedes, referring to the intense mental focus such a project requires. "As a pop-psychologist today would put it, you really need to be able to 'get into the zone,' and think about nothing else," he says. "It's all-consuming." "I think what [Tombaugh] did was a heroic task," says planetary scientist Alan Stern, the principal investigator for NASA's New Horizons mission to Pluto, scheduled to launch January 2006. Tombaugh's decade-and-a-half planet quest, Stern says, was unprecedented in its scope and the effort it demanded. "No one would stand for it today," he says. Indeed, modern searches are almost fully automated, with computers and imaging software taking over most of the mundane aspects of such work. In the 1930s, of course, the first computer was still more than a decade away. Stern says he is amazed not only "that a boy off the farm did what the professional astronomers couldn't accomplish in almost 30 years of searching," but also that Tombaugh "never once came to his boss with a false alarm -- he came to his boss precisely once." That was in mid-February 1930, after blinking a plate taken January 23 and another taken January 29, both from a region of the northern winter sky near the star Delta (δ) Geminorum. "And he had it," says Stern. "I think that's pretty amazing. He looked at thousands of plates, each one with thousands of stars, and many asteroids -- it's just mind-numbing what he did." The discovery's public announcement brought fame and accolades from around the world; the story was covered extensively in newspapers worldwide. Clyde Tombaugh would remain a celebrity in astronomical circles for the rest of his life. A genuine hero The news was especially welcome in Burdett, Kansas, where Tombaugh was celebrated as a local hero. The high-school principal, Charles Dilley, arranged a scholarship for Tombaugh so he could enroll at the University of Kansas, where he would eventually earn a master's degree in 1939. And it was also in Kansas that a young woman named Patricia Edson (Patsy, to her friends) first saw a photograph of her future husband. Patsy was also immersed in celestial matters, largely due to her brother James, an astronomy student who would be a classmate of Clyde's. "I lived in Kansas City, Missouri, and my brother, James, was going into astronomy," recalls Mrs. Tombaugh, now 92. "We were all going up to K.U. to get our college education." Newspaper headlines of Tombaugh's accomplishment grabbed everyone's attention. "My brother brought the picture of Clyde from the Kansas City Star and said 'You're going to meet that fella, because we're going to be classmates,'" she says. "So that's how I met Clyde." Patsy's own interests leaned toward art and philosophy, but with her brother and a small circle of friends -- including Clyde there were endless conversations about astronomy, space exploration, and life beyond Earth. "But we didn't talk to other people about it," she recalls, or they would have "thought you were out of your mind." They formed a club called, appropriately enough, the Syzygy Club (named for a term referring to the alignment of three astronomical bodies). Tombaugh's research took up enormous amounts of time, and being a celebrity planet-finder only added to the demands on him. But, says Patsy, none of this changed her husband's personality. "Clyde was a very down-to-earth kind of person," she says. "He didn't get egotistic about any of his accomplishments. He never changed his attitude toward people or life or anything. He was just Clyde." Pieces of a life Pluto's discovery triggered a search that would continue for over a decade.