Lowell Observatory Revisited

BY: Howard E. Boice, Jr.

(LEFT) Around the turn of the century, Percival Lowell used the observatory's original 24-inch Clark refractor to explore and map the planet Mars. COURTESY OF LOWELL OBSERVATORY (OPPOSITE PAGE) Star trails, created by a one-hour exposure, trace their arcs in the opening of the dome housing the 72-inch Perkins reflector on Anderson Mesa.

Astronomer Bob Millis stood anxiously by the compact 14-inch telescope, its bright orange color muted against the dark Australian sky. He and engineer Ralph Nye had traveled 10,000 miles to the high country of Queensland in 72 hectic hours from Lowell Observatory in Flagstaff, Arizona, to be here at this moment on June 9, 1988.

In less than a minute, the planet Pluto was expected to pass directly in front of a distant star. At that moment, Millis would know whether years of work-excruciatingly detailed work-would pay off or prove a failure. And no second chance. It was highly unlikely he would ever again have the opportunity to watch the planet Pluto-first discovered at Lowell in 1930-as it blocked the light of the star P8 in the constellation Virgo. Millis and his team hoped by observing this blocking, or occultation, to determine the exact size and shape of Pluto, whether it has an atmosphere, and whether rings of debris orbit the planet. Now, as he watched, Pluto began its move across the star. The long-awaited event was happening! First predicted in 1984 by astronomers at the Smithsonian Astrophysical Observatory in Massachusetts and the Lick Observatory in California, the occultation of Pluto began precisely on schedule.

Pluto's orbital path had been plotted during the preceding months and weeks by observing images of stars in the neighborhood of the moving planet. Astronomers at the Flagstaff Station of the

Lowell Observatory at 95

Text by Howard E. Boice, Jr. Photographs by Sean Brady Proud of its past, excited about the future.

U.S. Naval Observatory, using a superlative 61-inch telescope, produced more than 70 photographic plates with images of the star P8, planet Pluto, and about 90 surrounding stars.

Lowell astronomer Larry Wasserman measured these plates on Lowell's micro-densitometer to calculate the position of the planet in relation to various stars. By finding the centers of the stars, Wasserman determined the background position of each and the exact path of Pluto as it approached P8.

From this information, he anticipated where the shadow of Pluto would fall in Australia and the South Pacific. Millis, meanwhile, had alerted astronomers at existing telescopes in Australia and New Zealand. His own equipment was waiting at Sky Harbor International Airport in Phoenix, but Millis and Nye would not know for certain where they would be heading until the last minute.

To put Wasserman's computations into perspective, envision the earth as the size of a dime. Pluto would then be the size of a lead-pencil eraser 3½ miles away. The star P8 would be 6 feet across and several times as far away as the distance between the earth and the moon. (For purposes of calculation, P8 is assumed to be a stationary point of light, infinitely distant.) Now determine the precise movement of the shadow cast by the distant, eraser-size Pluto as it moves across the dime-size earth. Remember that Pluto and the earth are moving through space in different orbits, and, moreover, that the earth is spinning on its axis, an important factor. Then you have to pinpoint the place the shadow will fall at a given moment.

For two minutes, the mystery planet Pluto would block the light of P8, causing a thousand-mile shadow to sweep across the southern hemisphere of the earth, 4½ billion miles away.

Millis and members of seven other strategically placed teams of astronomers were ready to record the historic event.

Somewhat unexpectedly, the sensitive light-measuring devices on their telescopes indicated no abrupt reduction in the light emanating from P8 as the occultation began, but rather a gradual decline to zero as the blocking progressed. Seconds later, as the star began to emerge from behind Pluto, the needle again rose gradually rather than sharply as expected. Such a gradual change could mean only one thing to the astronomers: an extended atmosphere on Pluto was bending, or refracting, the visible light waves from P8. If the other teams had recorded similar data, Millis knew they had made a major discovery: Pluto was enveloped in a shroud of gas.

Although the existence of an atmosphere had been suggested by a few others, their assertion was not universally accepted, and nothing was known about the atmosphere's character and extent. That being the case, the occultation could change our whole picture of the physical properties of the ninth planet.

As quickly as he could, Millis conferred with the other teams-three in Australia (including one in Tasmania), three in New Zealand, and one near Pago Pago, flying high above the South Pacific in NASA's Kuiper Airborne Observatory, a converted C141 cargo jet with an on-board 36-inch reflecting telescope. The observation was confirmed. All had recorded the same phenomenon. Planet Pluto, slowly orbiting in the icy reaches of the solar system, had revealed one more important tidbit of information to the tenacious scientists probing its secrets.

But their effort to measure precisely Pluto's size and shape was foiled, ironically, by the very atmospheric mask they had discovered.

It was fine justice that a team from Flagstaff's Lowell Observatory would make this discovery, just as it was that a similar team effort directed from Lowelllargest privately funded astronomicalinstitution in the world-had confirmed the existence of Pluto (then called Planet X) some 58 years before. In that instance, a young high school graduate, Clyde Tombaugh, spent a cold winter in the unheated hilltop observatory on Flagstaff's Mars Hill making photographic plates of the sky in a systematic search for the elusive body. The observatory's founder, Percival Lowell, a proper Bostonian and true Renaissance man, had predicted the location of Planet X some 20 years earlier. He based his prediction on a "wobble" in the orbits of Pluto's closest planetary neighbors, Neptune and Uranus.

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Lowell Observatory

Lowell hired five Harvard mathematicians who spent seven years calculating the complex formulas that indicated a probable orbit for Planet X. He did not live to see the results of his pioneering work; but the team he assembled in Flagstaff pursued Lowell's dream after his death in 1916 and, 14 years later, brought it to reality. Lowell's legacy has changed the way humankind thinks of itself and its origins. It was Percival Lowell's handpicked successor at the observatory, Vesto M. Slipher, who discovered the "red-shift" phenomenon of distant galaxies, which led to astronomers' understanding of a constantly expanding universe.

Among the ongoing research at Lowell is a program to analyze variations in solar radiance by observing the reflected light from the Galilean moons of Jupiter and comparing the luminosity variations with those of other sunlike stars. Through this study, Lowell's Wes Lockwood is gathering data that is leading to a better understanding and possible prediction of solar storms that interfere with communications on earth-a vital concern to the Department of Defense and NASA, among others.

Other research involves comets, asteroids, planetary atmospheres, star formation, binary stars, rapidly oscillating stars, and the evolution of galaxies. Lowell astronomers are also partners in the science teams for the Hubble SpaceTelescope, scheduled for launch in 1991.

Founded in 1894, the observatory for nearly a century has been an important part of the world's scientific community. Never has it been more active than it is today.

Jay Gallagher, an energetic and enthusiastic scientist, directs the observatory's activities and manages its precious resources even as he pursues his own research into galactic origins and evolution. He is excited about the institution's work and its past, but mostly its future.

Lowell, he says, is a discovery-oriented institution. He divides research at Lowell into three major categories: planetary, stellar, and galactic.

There are 12 resident astronomers with a support staff of about 20, including technicians and mechanics. Principal funding comes from Percival Lowell's endowment to the institution, private foundations, and grants from or contracts with various agencies, including NASA, the Department of Defense, and the National Science Foundation. Nonfederal sources account for about a third of the observatory's funding.

Gallagher says a growing concern among the astronomers is that heavy dependence on government grants makes research susceptible to shifts in political winds, making long-term projects difficult to plan and finance.

Another worry is that such dependence could put federal agencies essentially in control of Lowell's research priorities.

"Clearly, the funding ratio between private and federal monies should be reversed," the director says.

Recently, observatory trustee William Putnam Lowell, a grandnephew of Percival Lowell, approved a plan to seek more outside funding-a move that has led to a strengthening of programs to generate public interest in the observatory's research and to show the ways in which it benefits society.

The Planetary Research Center at Lowell is one of two designated depositories of planetary studies in the world and the only one in the United States. The center was headquarters for the worldwide Planetary Patrol Program of the 1970s. Here, in one location, a visiting scientist or researcher can find images and data from the most recent observations to those of the last century.

At the center, I was able to thumb through some of Percival Lowell's original journals of his Mars observations, including those of the controversial "canals." (Percival Lowell achieved fame and stirred controversy with his turn-of-the-century conclusions that certain features on Mars were canals that indicated the possibility of intelligent life there.) Three feet away, I found recent photographs and images of Mars transmitted from its surface by the Viking spacecraft.

Lowell Observatory occupies a site atop a pine-covered hill within the city of Flagstaff. It also operates telescopes on Anderson Mesa, 12 miles southeast of town, across from Lower Lake Mary.

A 24-inch Clark refractor, Lowell's original telescope, dominates the Mars Hill site. The building that houses it was constructed of wood in 1896 by local carpenters who worked to Lowell's exacting specifications. The instrument was used continually for scientific observations until just a few years ago. Now it is reserved primarily for public viewing as part of the stepped-up public program.

Lowell Observatory

The nearby visitors center, Lowell's original library, is a delight to anyone who appreciates fine stonework and wood craftsmanship and design. Displays, including the original plates from which planet Pluto was discovered and a meteorite that crashed to earth ages ago, ring the circular room.

Two modern buildings blend unobtrusively into the pines. Both were built during the active "space race" period of the 1960s, when Lowell Observatory played a major role in mapping the Apollo missions to the moon. Nearby housing for staff is hardly visible in the sylvan setting, which the human residents share with the native flora and fauna-including Abert squirrels, who will chatter up a storm of disapproval if an intruder disturbs them.

There are four telescopes on Mars Hill and five on Anderson Mesa. The latter group includes a new and tiny 200-micron (1/100 of an inch) solar instrument used to compare energy from the sun with light from stars of similar character.

At Anderson Mesa, Lowell operatesin a joint program of long standing with Ohio State University-the 72-inch Perkins reflector. During the summer of 1988, while the annual monsoon season obstructed viewing, the Perkins was updated with state-of-the-art computer and telecommunications ware to allow for remote operation by Ohio State scientists from their own facilities in Columbus, Ohio. Some day soon, astronomers envision being able to operate many of the world's best viewing instruments remotely.

Lowell Observatory is kinetic-always changing, moving, a kaleidoscope of modern scientific activity and inquiry. In a steady stream, top scientists from around the world travel to the cool alpine setting of Flagstaff, often passing en route astronomers from Lowell on their own tempo-rary quests elsewhere. The search for knowledge is never-ending at Lowell Observatory, one of Arizona's undisputed treasures-a venerable institution that has contributed mightily to humankind's understanding of the universe of which we are such a tiny part.

Author's note: Tours and public programs, including viewing through Lowell's original 24-inch Clark refractor, are available year around. The schedule varies; the observatory staff recommends that you call ahead to (602) 774-2096 for current tour and program hours.