Sky Writer

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Fortunately, Tombaugh proved to be more than simply a hired hand. On February 18, 1930, Tombaugh brought glory to Lowell Observatory by discovering the only major planet found this century.

It was named Pluto. (But Lowell was not vindicated: Pluto was much too small to be his predicted Planet X.)

Now, in the late 1950s, with Tombaugh no longer associated with the observatory and his planet search long over, Henry Giclas had conceived of a way to make additional use of Tombaugh's labors.

He would take a series of long-exposure photographs of the sky, each on a glass plate corresponding with one taken by Tombaugh 30 years earlier. In that time, some of the stars would show movement. The closer ones would, anyway, just as when motorists see objects that are closer whiz by faster than distant ones.

Identifying that movement--called "proper motion"--was the best way to determine which stars were closest to the sun, valuable data for scientists who wanted to know what kind of stars a typical portion of the galaxy--namely our own--contains.

Soon after the project got under way, Giclas learned about the Prescott amateur who had discovered a comet, and decided to hire him.

But only, Giclas says, after Burnham's mother apologized to the observatory for writing the unsigned article in the Courier.

"I couldn't hold it against Burnham," he says.

In 1959, with the continuation of his graduate studies in astronomy jeopardized by a lack of funds, Norm Thomas packed up his family of four and left Berkeley, California, for a job at Lowell Observatory.

There he was paired with Robert Burnham Jr., who for the past year had been working on the proper-motion survey with astronomers Giclas and Charles Slaughter.

Day after day, Thomas tried to trip up his taciturn and brilliant partner.
Sometimes he succeeded. Other times, Burnham came out on top.
Their competition would produce the most widely cited proper-motion survey in history.

Now that the project was running smoothly, Giclas and Slaughter turned it over to the two young men who lacked advance degrees in the field.

Both Burnham and Thomas were told not to expect the survey to last longer than three years.

Instead, it would last another 20.
Mostly, that was because of how well Burnham and Thomas worked together. Their success impressed the National Science Foundation, which continued to fund the project.

"Henry [Giclas] was quite good, but he was a little impatient with it," Thomas says, adding that because Giclas wasn't a "blinker" by nature, he wasn't taking the project to its full potential.

To explain what he means, Thomas descends into the basement of one of Lowell Observatory's oldest buildings where thousands of glass plates in white envelopes line the walls of a cramped room.

Against one wall is a contraption called a "blink comparator." The machine held two glass plates at a time, one dating from the 1930s search for Planet X, the other exposed by Burnham or Thomas themselves. Corresponding postage-stamp-size regions from each plate were projected onto a screen, first from one plate and then the other, back and forth, clickety clack, endlessly.

With the plates lined up correctly, the stars in each portion projected on the screen would hold still. Even in the 30 years between exposures, most stars seemed fixed in their positions and showed no movement. But occasionally, in a particular field on the plates, Burnham or Thomas would notice a star make a subtle leap.

Thomas shows how he would mark the star with a dab of India ink, hoping that Burnham had missed it. After Burnham, using another, fresh plate, had made his own search, the two of them would compare notes, tallying up the moving stars, particularly the ones that the other had missed.

"That did provide something fun. Who would miss something really neat. It was a competition," he says.

By the time the program ended in 1979, they would identify 9,000 high-motion stars as well as several comets, 1,500 asteroids and 2,000 new white-dwarf suspects--degenerate stars with incredible densities--as well as thousands of variable stars which they simply had no time to study.

Thomas describes it as a merry-go-round of activities. While one of them blinked during the day, the other would expose new plates at the 13-inch Pluto discovery telescope at night. Plates had to be developed, leaping stars identified and tabulated, and finder charts had to be made for the high-motion stars and white dwarfs so other astronomers could recover them in the sky. Both of them were also expected to help out by giving tours to visitors.

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Tony Ortega
Contact: Tony Ortega