Discoverer of Pluto, 84, Still Combing the Skies

Sixty years after he discovered the planet Pluto spinning 3 billion miles from Earth, Clyde Tombaugh can’t keep his hands off telescopes.

At age 84, Tombaugh is supposed to be retired, resting on his laurels as one of only four people ever to have discovered a planet.

Instead, the snowy-haired astronomer is still crisscrossing the country, lecturing about Pluto to raise funds for postdoctoral astronomy students at New Mexico State University, where he taught for 12 years.

And he is still building telescopes, which is how the former farm boy got started in astronomy in the first place. At the moment, he is working on one for his 16-year-old granddaughter.

“I’m going to have her do some of the polishing, and have her test the curve,” he says. “She’s going to get a good introduction to it.”

Tombaugh has no hobbies that are not related to astronomy, his lifelong love. “I’m always interested in making telescopes, grinding mirrors and so on,” he says. “I love that.”

On a recent lecture stop in Spencerport, the planet hunter handled a throng of elementary school students with the experienced patter of a cornball comedian.

“That’s a very good question!” he told a girl who asked how Pluto got its name. The name was chosen by scientists at Lowell Observatory, where the planet was discovered, he says. Then, with his face crinkling into a wide grin, he adds:

“Some people think it’s named after Pluto the Pup. Of course there’s no connection. I think the planet came first--I’m not sure.”

“How cold is Pluto?” a student calls out.

“The air that you breathe--nitrogen and oxygen--would be frozen solid rock on Pluto,” Tombaugh says. “It’d be a little hard to breathe, wouldn’t it?”

Tombaugh was just 24, fresh off his family’s Kansas wheat farm with only a high school diploma to his name when he discovered Pluto in 1930. Six decades later, the discovery remains his proudest achievement.

Tombaugh got interested in astronomy in the sixth grade, when his favorite subject was geography. “I wondered what the geography was like on other planets and I’ve been at it ever since,” he says.

In high school, Tombaugh built a telescope and spent long hours making careful drawings of Mars and Jupiter. He wanted to be an astronomer, he says, but his family didn’t have the money to send him to college.

In 1929, Tombaugh’s drawings got him hired on a trial basis as an assistant at the Lowell Observatory in Flagstaff, Ariz. He was to help search for a trans-Neptunian planet with the observatory’s new 13-inch telescope.

Of the nine planets now known to be circling the sun, six had been known since antiquity. The English astronomer William Herschel discovered the seventh, Uranus, in 1781. Two people are credited with the discovery of Neptune, the eighth, in 1846--the English astronomer John C. Adams and the French mathematician Urbain J. J. Leverrier.

The existence of a ninth planet was predicted in 1915 by Percival Lowell, who believed “Planet X” was causing deviations in the orbits of Uranus and Neptune.

Tombaugh’s job was to compare 14-by-17-inch-photographs of the night sky on a device called a blink-microscope-comparator, which rapidly switched between two images taken several days apart. If a planet were visible, it would have moved to a new position in the second photograph. In more crowded areas of the universe, such as the Milky Way, more than 2,000 stars filled every square inch of the photograph. Each had to be examined for even the most infinitesimal movement.

“It was tedious,” Tombaugh says. “But it was much more interesting work than farming, as far as I was concerned.”

On Feb. 18, 1930, Tombaugh found what he was looking for. A tiny dot of light had moved an eighth of an inch.

“It electrified me,” he says. “In one split second, I realized I’d be world famous and turn the scientific world upside-down. It was a tremendous feeling.

“I was excited, but I didn’t go around yelling. I figured it’d just alarm everybody. It alarmed them plenty when I told them I found a planet.”

As it turned out, Lowell’s prediction of Planet X’s location had just been lucky. Pluto--now estimated to have about 0.2% of Earth’s mass--is much too small to cause irregularities in the other planets’ orbits.

For finding Pluto, the novice astronomer got a $10 raise and a nominal prize from the Royal Astronomical Society in Great Britain.

Later, Tombaugh got a master’s degree in astronomy from the University of Kansas and continued combing the skies--discovering a globular star cluster, a supercluster of galaxies, several lesser clusters, one comet and about 775 asteroids, one of which bears his name.

Tombaugh lives in Las Cruces, N.M., with Patricia, his wife of 56 years, and a mostly black cat named Pluto. He wears a watch his son had made for him, which features Walt Disney’s cartoon dog Pluto.

Tombaugh doesn’t put much stock in speculation that a 10th planet exists. It could be out there, but it would have to be very small or very far away for him to have missed seeing it on his plates, he says.

“It’d be interesting to see if they ever did find one, but it’s going to be some hard digging,” he says. “Actually, I’m a little pessimistic about it.”

Tombaugh says he has looked at 45 million stars in his lifetime--more than two-thirds of the visible universe. He has seen more of the heavens’ starry expanses than perhaps anyone else.

“I had a grand view of the universe,” he says.