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Clyde Tombaugh

Photograph of Clyde Tombaugh with telescope

Discoverer of the planet Pluto. Born: February 4, 1906, Streator, Illinois.  Died: January 17, 1997, Las Cruces, New Mexico.

Fifty miles west of Great Bend, down K-156 highway, is the small farm community of Burdett. In the shadow of the water tower is a roadside park with a large metal historical marker devoted to Clyde W. Tombaugh, the discoverer of Pluto.

Clyde W. Tombaugh was born in 1906 in Streator, Illinois. In 1922 his family moved to a farm near Burdett. As a youngster, his interest in astronomy was encouraged by his father and uncle. Tombaugh was a self-taught amateur astronomer who made his own telescopes from hand ground mirrors and parts of farm equipment. He graduated from Burdett High School in 1925. In 1928 Tombaugh made a nine-inch telescope that enabled him to make very accurate and detailed sketches of Jupiter and Mars. Seeking advice from professional astronomers, he sent his sketches to the Lowell Observatory in Flagstaff, Arizona. As coincidence would have it, the Lowell staff was looking for an amateur astronomer capable of operating their new photographic telescope. They were sufficiently impressed with his work to offer Tombaugh the position on a trial basis.

Like many farm folk of that time, Tombaugh had never traveled very far from his home. In early January 1929 he boarded a train for Flagstaff. Tombaugh wrote:

After spending 28 hours in a chair car on the Santa Fe, I arrived at Flagstaff in the early afternoon of 15 January, 1929. Dr. Slipher met me at the depot and drove me up Mars Hill. The yellow pine forest was in stark contrast to the treeless plains of Western Kansas. I was rather unnerved by it all, everybody were strangers, 1,000 miles from home, and not enough money in my wallet for a return ticket home . . .

Little did he know that the three-month trial period would turn into 13 years at the Lowell Observatory.

Prior to 1781 everyone knew that the solar system was composed of six planets. In March of that year William Herschel became the first person in recorded history to discover a planet. The discovery of Uranus was a glorious achievement for astronomy, however, there was a small problem. Uranus did not seem to want to conform to the laws of Newtonian physics. The planet's behavior defied predictability, and no one seemed to be able to explain this erratic behavior. In 1824 Friedrich Bessel of Germany suggested that another planet beyond Uranus would explain the problem. By 1830 it had become generally accepted that another, yet undiscovered, planet existed. Finally, on September 23, 1846, the planet Neptune was discovered by Johann Galle at the Berlin Observatory.

Neptune helped to explain the difficulties in predicting the orbit of Uranus and vindicated Newton's laws — in part. There still existed a couple of minor problems, but this time almost everyone agreed that there must be another planet beyond Neptune, which would explain the difficulties. Unfortunately, it was too distant, too dim, and probably impossible to find.

Enter Percival Lowell. Lowell was born into a wealthy Boston family and attended Harvard. He became a very successful businessman and traveled extensively. He eventually turned to a serious pursuit of astronomy and in 1894 he built the Lowell Observatory at Flagstaff, so he could study the planet Mars. In 1905 Lowell began his search for the ninth planet, which he labeled "Planet X." By 1908 another American, William Pickering, was also engaged in the quest to find the mysterious planet. Pickering had helped Lowell establish his observatory but had distanced himself after Lowell became convinced that intelligent life existed on Mars. Sadly, Percival Lowell suffered a massive stroke and died on November 12, 1916, without sighting the planet he had devoted many years to locating.

Lowell left an endowment of more than a million dollars to keep his observatory operating. In his will he named his assistant, Vesto Slipher, director of the observatory. Lowell's widow contested the will, and the court battle to settle the estate—which would consume most of the endowment—lasted until 1927. Slipher prepared to resume the quest for Planet X by having a new and more powerful telescope installed. It would be a tedious task involving spending long hours in the unheated dome taking exposures of the sky and then trying to detect a minute shift in one of the thousands and thousands of points of light that would identify a planet. This is the task the observatory hired Tombaugh to perform.

To detect the movement of an object in the sky involved taking two photographs of the same section of the sky several days apart using the observatory's 13-inch astrograph. The plates were then placed in a device called a blink comparator that "blinked" back and forth between the two plates at a speed to make the two appear as one. Any object that has moved between the frames would be the elusive planet. Each photographic plate could contain more than 150,000 stars, and those taken of the Milky Way could contain close to a million. It took Tombaugh up to a week to examine each pair of exposures.

Late in the afternoon on February 18, 1930, the 24-year-old Tombaugh was gazing into the eyepiece of a Zeiss Blink microscope at photographic images of a star field, examining a pair of plates taken in mid-January. Suddenly the monotony was broken when his attention was caught by one of the millions of minute specks of lights whose image had moved slightly between one photograph and the next. He checked and rechecked his photographs for 45 minutes before calling his supervisors. He knew he had found Planet X. The observatory staff watched the star for a few weeks to confirm the movement, and on March 13, 1930, the discovery of the ninth planet was officially announced. Front page headlines around the world heralded the discovery. The name for the new planet was suggested by a young schoolgirl from England. She thought that because the planet was so far away from the sun and in its own dark world, it should be named for the Greek god of the underworld, Pluto, which was announced May 1, 1930.

Tombaugh went from being an anonymous planet hunter to an internationally famous astronomer over night. On the heels of his discovery, Tombaugh received an offer of a scholarship for the University of Kansas University, which he accepted. He went on to earn degrees from KU and Northern Arizona University. He concluded his career as an astronomy professor at New Mexico State University. He is credited with the discovery of several galactic star clusters, hundreds of asteroids, a comet, a cluster of 1,800 galaxies and other observations. Tombaugh died January 17, 1997.

By the early 21st century many more objects of Pluto's size were discovered. In 2006 the International Astronomical Union officially defined the term planet and Pluto was determined to be the second-largest dwarf planet, and tenth largest body orbiting the Sun.

Entry: Tombaugh, Clyde

Author: Kansas Historical Society

Author information: The Kansas Historical Society is a state agency charged with actively safeguarding and sharing the state's history.

Date Created: June 2003

Date Modified: February 2013

The author of this article is solely responsible for its content.