By Jeff Berg
If I wanted to feel younger, I could perhaps take a quick trip to my favorite planet, Pluto, which would take only five to seven years and cover a mere 3.647 billion miles. Once I got there, not including the travel time, I would be only 3,042 Plutonian days old, and 0.214 Pluto years in age, and my next birthday would not be until what would be May 25, 2200, back here on Earth—one long, dark journey for Pluto around the Sun.
This month, on the 18th to be exact, is the 75th anniversary—that's in Earth years—of the discovery of the planet Pluto. The distance from Las Cruces to Pluto turns out to be not so very long at all, at least in the "degrees of separation" sense: Long-time NMSU professor and Las Cruces resident Clyde W. Tombaugh discovered the planet, formerly known as Planet X, when it was just a lingering suspicion. Tombaugh was an amateur astronomer when he discovered the last recognized planet in our solar system, while working at the Lowell Observatory, which is now connected to Northern Arizona University (NAU) in Flagstaff.
Astronomers had long thought that a ninth planet existed in our solar system, and Pluto, named for the god of the underworld (as well as in homage to astronomer Percival Lowell, whose initials begin "PLuto" and are its astronomical symbol), was indeed that Planet X. Almost 100 years had gone by between planetary discoveries, with Neptune being documented by Johann Gottfried Galle and Louis d'Arrest in 1846, based upon the mathematical calculations of Urbain Jean Joseph Le Verrier.
Percival Lowell, who originally built the observatory now named after him, was the one who labeled the hypothetical planet as "X," and searched for it without success throughout the early 1900s. Although two weak images of the planet were recorded in 1915, they were not recognized until after Tombaugh's discovery in 1930. Another noted astronomer, William Pickering, also sought Planet X without success.
The smallest recognized planet, Pluto has one moon, Charon (named after the mythical boatman who ferried the dead across the River Acheron into Hades), which was not discovered until 1978, since images of the two globes always blurred together. Pluto has a rotation time of 6.38 days and is 1,485 miles in diameter. No amount of layering could keep you warm on this icy sphere, which is an enticing blend of one-half to three-quarters rock and a large amount of various types of ice. The average temperature is thought to be minus-375 degrees Fahrenheit (a balmy-sounding minus-195 Celsius), with a bright southern polar ice cap. With a mass (the amount of "matter" an object contains causing it to have weight in a gravitational field) roughly one-fifth that of our Moon, Pluto is a lightweight among planets. Pluto is so small that it is overshadowed in size by seven moons of our solar system.
The speculation about Pluto's existence heightened as sky observers noted that the motions of Neptune and Uranus (no jokes, please) "required" there to be another planet beyond Neptune. The orbit of Pluto indicates that this theory was correct, as the little ball of icy rock crosses Neptune's orbit in a long ellipse. During the planet's 249-year orbit of the sun, 20 years of that time find Pluto closer to old Sol than Neptune is.
Clyde Tombaugh was born in 1906 in Streator, Ill. When his family later relocated to Kansas, he became interested in astronomy through a relative. In 1928, "armed with a homemade nine-inch f/9 reflector of superb optical quality," Tombaugh made sketches of the planets, predominantly of Mars, Jupiter and Saturn. He sent copies of these sketches to the Lowell Observatory, in hopes of receiving comment about his study. Instead, V.M. Slipher, who was the director of the observatory, offered the 22-year-old a position to take photos of the skies—photos that would eventually lead to the discovery of Pluto.
A few months after Tombaugh arrived, Slipher also assigned him the task of scanning the photographic plates with a blink comparator, "a device which allows someone to compare two similar photographs by placing them in the viewer's field of vision, and then letting the user switch back and forth—blink—between the two." In 1929, Tombaugh had rebuilt the program to allow for easier searching. And on Feb. 18, 1930, at 4 p.m., he was rewarded: While scanning a pair of plates centered on the Delta Geminorum (a dwarf nova), he noticed a "speck of light shifting from plate to plate exactly as a trans-Neptunian planet should."
It should be noted that a plate could have as many as a half-million stars on it. . . .
After discovering a planet at the tender age of 24, Tombaugh went on to earn astronomy degrees at NAU (formerly Arizona State College, ASC) and at the University of Kansas. After teaching at ASC and the University of California at Los Angeles, Tombaugh moved to New Mexico in 1946, and (no pun intended) became a rocket scientist at White Sands, earning $4,900 a year. Part of his job was to select sites for tracking telescopes that were used to watch missile launches. His official title at White Sands was "Chief of the Optical Measurements Branch in the Ballistics Research Laboratory." The study included observation of German V2 rockets.
Although his position at White Sands allowed him to work with optics and telescopes there, Tombaugh found himself longing for a return to "planetary work." (He had also discovered 14 asteroids while working at Lowell.) The opportunity again presented itself when, in 1952, the new director of the Lowell Observatory, Albert Wilson, asked him to return to the observatory. There was a new plan to do a survey "for stars of high proper motion"—defined as the "apparent angular rate of motion of a star across the line of sight on the celestial sphere." Returning to Lowell, Tombaugh was soon comparing some of the new plates he had shot with some from 1936, thus discovering a treasure trove of new information that would help plot the information needed to calculate a star's distance from Earth.
Tombaugh had married Patricia Edson in 1934. "Patsy" was the sister of a friend, James Edson, whom Tombaugh had met at the Syzygy Club, a community of astronomy students at the University of Kansas. They were married for more than 62 years, until his death in 1997.
Patsy Tombaugh, who still lives in Las Cruces, recalls, "I had my degree in philosophy, but my job was taking care of him and our two children. I did a lot of volunteer work, and also helped him with his research."
The Tombaughs' two children also both still live in Las Cruces. "Our daughter (Annette) is a teacher who retired after 30 years, but still does tutoring on the side," Patsy Tombaugh says. Alden, their son, is a retired banker, who is now dabbling in the construction business, with his company called Planet Development Co.
"We have five granddaughters, but no grandsons, so the Tombaugh name will not be carried on in that way," Patsy Tombaugh adds. "We also have nine great grandchildren, six boys and three girls."
Clyde Tombaugh had left White Sands and returned to Lowell full-time, until he figured out that Lowell wanted to use him only for his "blinking" experience. He felt that the administration of the Lowell Observatory was losing interest in its work on the planets, and decided to move on, returning to New Mexico. He came to New Mexico State University in 1955.
NMSU had housed hit-and-miss programs in astronomy before, notably led by Professor Hiram Hadley in 1888 (even though this was before NMSU was actually recognized), and Clarence Hagerty, who'd headed a small astronomy department in 1925. But Tombaugh restarted NMSU's astronomy program and launched the Planetary Group, an astronomy research program.
Originally working from an office within the school's library, the Planetary Group had five members by 1961, teaching astronomy and planetology as part of the Department of Geography and Geology. Although Tombaugh was never the department head, it was certainly not because he did not have the knowledge to do so. His career had yet to lead to earning a PhD, and his math and physics knowledge would normally be considered to not be "competitive for a modern department," according to David Levy, Tombaugh's biographer. But Tombaugh's disinclination to be department head came more from a distaste of administrative work, as opposed to experience or credentials. Levy in his book quotes former department head Herb Beebe: "The fact that he didn't have a PhD wouldn't have stood in the way."
During his years at NMSU, Tombaugh became the point man in designing and finding funds to build the university's Tortugas Mountain Observatory. The observatory has a 24-inch telescope, which currently helps obtain data for NASA.
According to a 1997 article by Karl Hill of NMSU, "Tombaugh never lost his passion for stargazing. When the Smithsonian Institute asked if it could have for its museum the telescope he made in 1928, 'I told them I was still using it,' he said in an interview. The nine-inch telescope, with which he made the drawings that impressed the Lowell Observatory staff, was built with parts of discarded farm machinery and a shaft from his father's 1910 Buick. Until frail health prevented it, Tombaugh continued observing the heavens through that nine-inch telescope and a larger one he made himself, from his back yard in Mesilla Park."
In 1970, after years of work by Tombaugh, the astronomy department became a separate department on the NMSU campus. Currently it has eight tenure-track faculty members, does work for the NASA Planetary Data System, and manages the Apache Point Observatory in Sunspot, NM. The department also sponsors public open houses each month, with the next one scheduled for the Pluto anniversary date of Feb. 18 at 7 p.m. at (where else?) the Tombaugh Observatory. (Call 646-4438 for more information.)
Tombaugh's work at NMSU continued to bring him into new areas of planetary research. From 1956-58, he was associated with the Satellite Search Project, which was based in Ecuador. The purpose of this project was to try to photograph Sputnik I, the first manmade satellite. In 1959, it was partially through Tombaugh's work that the final report on the Near Earth Satellite Search was issued. The positive result of this report was to show that rockets could be launched "into space without colliding with natural debris."
From 1958 until 1973, the Planetary Patrol, which was initiated by Tombaugh, existed to take photos of all of the planets except for Neptune, Uranus and, of course, distant Pluto.
But life was not all work for Tombaugh, who was also a very spiritual man. He and Patsy were founding members of the Unitarian Universalist Church of Las Cruces, and remained active in it for many years. In 2001, a stained-glass window was dedicated to Tombaugh in the church at 2000 S. Solano Drive; the window's theme is, of course, the solar system. Multi-paneled, the window depicts different areas of his life, from his boyhood to rockets and teaching and working with telescopes. Since Tombaugh was well known for his affection (affliction?) for bad jokes and puns, a crow is included in the window—crows being a favorite target for his humor and word play. The church has also honored Tombaugh by naming its gallery after him.
"By the time he retired, he and his NMSU astronomy staff had confirmed the rotation period of Mercury on its axis, determined the vortex nature of Jupiter's Great Red Spot, and developed a new photographic technique for the small Earth satellites search he was supervising," according to interviewer Hill.
"He retired at 67, which was the mandatory retirement age at that time," Patsy Tombaugh recalls. "But he still had an office on campus that he went to every day for many years afterward."
Though officially retired in 1973 and named an emeritus professor of astronomy, Tombaugh was not one to sit still. From then until his death, he remained active by writing an autobiographical book about his discovery of Pluto, Out of the Darkness, and went on a lecture tour in the late 1980s to raise funds for the Clyde Tombaugh Scholar Fund, which was started in 1986.
Several years before his death, the Clyde Tombaugh Elementary School opened in Las Cruces. Patsy Tombaugh recalls the day they went to the dedication: "Clyde said, 'My, it is so big!' And I said to him, 'Well, what did you expect, a little red schoolhouse?'"
It was not until he was in his mid-90s that failing health forced Tombaugh to slow down. But perhaps it was time to take it at least a little easy, since during his career, he had photographed 65 percent of the sky and examined millions of star images, discovered a comet, a number of star clusters and numerous asteroids. And, of course, a planet.
Clyde Tombaugh's biggest personal discovery throughout his life, however, might have been his never-ending sense of awe, curiosity and wonder at the possibilities of the universe. In one of his final interviews, before his death on Jan. 17, 1997, he spoke with the Academy of Achievement about the possibility of life in other galaxies:
"You do believe there are alien civilizations out there?" the interviewer asked.
Tombaugh replied, "Oh yes. Our sun couldn't be so peculiar as to be the only one, out of octillions of stars, to have a planet with life on it.
"That's totally against the odds, even if you have only one star out of 10,000 that has a planet that is right for life. We know now from sampling with big telescopes, that the number of stars in the skies is 10 to the 21st power. Now that doesn't mean anything until I tell you that the number of grains of sand in all of the earth's ocean beaches is only ten to the 19th power. So there are a hundred stars to every grain of sand in all the ocean's beaches. You have to realize there's this enormous potentiality of trillions of planets out there with alien civilizations on them. We are not the center of the universe. We are not all that important. And we're not alone. That's my perspective.
"You see these things in the sky in your plates and it's a wonderful education. You're made aware of the enormous vastness of the universe and all of the things that may be in it. That to me is a very challenging thought. I love to dwell on that, that wonderment."