The Harlan J. Smith Centennial Professorship in Astronomy

In 1983 a private donation to the Centennial Teachers and Scholars Program was made by an Anonymous Donor establishing the Edward Randall, Jr., M.D. Centennial Professorship in Astronomy. The University of Texas System Board of Regents matched this donation, and the Anonymous Donor designated that the matching funds be used to create another professorship in astronomy honoring Dr. Harlan J. Smith.

Harlan J. Smith

Harlan J. Smith, Director of McDonald Observatory since 1963, has attained worldwide recognition as an astronomer, researcher and administrator of one of the world's finest observatories. In 1983, to acknowledge his outstanding career Smith was appointed the Edward Randall, Jr., M.D. Centennial Professor in Astronomy. So that another individual might carry on his tradition of excellence, Smith has been further honored with the creation of a professorship in his name. The first recipient of the professorship is William H. Jefferys, former student of Smith's and long-time colleague.

Smith was born in Wheeling, W. Va. He first became interested in optics as a small boy when, while looking through a six-inch telescope that had been donated to the town, he realized that the image of a nearby gas station sign appeared upside down. He earned his undergraduate degree in physics and graduate degree in astronomy both from Harvard University. In 1953, while finishing his thesis on short-period cluster-type variable stars, he began teaching at Yale. Ten years later, while an Associate Professor at Yale, Smith was offered a challenging opportunity in Texas. He accepted the position and, on the eve of Labor Day in 1963, Smith arrived in Austin to take on the dual responsibilities of Chairman of the Department of Astronomy at The University of Texas and Director of McDonald Observatory.

His first order of business was to initiate conditions to nurture the growth of the Department of Astronomy, both to make it competitive with other astronomy departments in the country, and to take advantage of the facilities of McDonald Observatory. He recruited new faculty, at first drawing on New England connections and later reaching throughout the United States and beyond.

In the late 1960s, strong national interest in space sciences motivated the National Science Foundation to sponsor a program to generate new centers of academic excellence. Thanks in part to the persistence of Smith, Texas received the largest single grant and began to attract additional bright, young astronomers.

During that period, Smith also shepherded the growth of the astronomy graduate student program and the astronomy undergraduate teaching program; both are now the largest in the United States.

Meanwhile, he was working to improve the facilities at McDonald Observatory. At first, with support from The University, and later with help from NASA, he rejuvenated the 82-inch telescope. In 1965, NASA, the National Science Foundation, and The University of Texas funded the construction of a new 107-inch telescope. Smith, with his customary thriftiness, later used the glass cut from the inside of the 107-inch to make the mirrors for two additional 30-inch telescopes.

Close co-operation with NASA's planetary studies resulted in the laser ranging program. For years, it was the only successful lunar ranging program and used a Korad laser attached to the 107-inch telescope. In 1981, the laser ranging program was moved to an independent 30-inch telescope at the McDonald Observatory complex using a new laser system, and, in 1985, Smith presented the old Korad laser to the Smithsonian Institution for display with other historical astronomical instruments.

The first astronomers to come to The University of Texas in 1963 included (from left to right) Harlan Smith, Gerard de Vaucouleurs, Robert Tull, Terry Deeming, and Frank Edmonds.

Smith also recognized the benefits of an association with an active radio astronomy group. He persuaded James Douglas to come from Yale to Texas, and he supported Douglas' idea for a new kind of radio telescope which would accurately pinpoint the locations of radio sources. The University of Texas Radio Astronomy Observatory, with its Two Mile Telescope at Marfa, resulted. About the same time, McDonald became associated with another kind of radio telescope, one which detects millimeter waves from cold clouds of gas and other objects in space. Today, the millimeter telescope on Mount Locke is operated jointly by the Department of Astronomy and The University of Texas Department of Electrical Engineering. Smith continues to keep an eye on radio astronomy, with the idea of developing it further within the next couple of decades to study the backside of the moon.

The expansion of humanity into outer space has long fascinated Smith. His enthusiasm for space endeavors was a contributing factor in UT having more scientists working on the Hubble Space Telescope (HST) than any other institution.

In addition to his quarter-century of service to McDonald Observatory, Smith holds honorary doctorates from Nicholas Copernicus University in Torun, Poland, and from Denison University in Granville, Ohio. He is a member of many distinguished organizations including the Royal Astronomical Society, the International Astronomical Union, and the American Association for the Advancement of Science (Fellow, 1983). He has served as Vice-President of the American Astronomical Society and Chairman of its Planetary Division, also as Chairman of the Committee on Space Astronomy and Astrophysics of the Space Science Board. He has served on astronomy panels for NASA and the National Science Foundation. He is a former chairman of the Board of Directors of the Associated Universities for Research in Astronomy (AURA).

Smith has done research in many areas of astronomy including variable stars, photometry, instrumentation, planetary astronomy and quasars, and has some 70 publications including editorship of several books.

Harlan and his wife Joan have four children, Nat, Julie, Tad, and Hannah. Some other interests include China, beekeeping, and windsurfing.

Harlan Smith likes to say that McDonald Observatory stands on four solid legs: its excellent research facilities for professional astronomers, its strong graduate student program, its equally strong program for undergraduates, and its outreach programs for the general public. He should know. He was the architect for the expansion of each of these areas into its present form. More than any other person, Smith is responsible for the remarkable growth of McDonald Observatory, and for its present status as one of the world's great centers for astronomy.

Message from the President

On behalf of The University of Texas at Austin, I express appreciation for the generous gift establishing the Harlan J. Smith Centennial Professorship in Astronomy. This professorship honors Dr. Harlan J. Smith for his dedicated service to furthering excellence in astronomical research and education at The University over the past 23 years.

The goals of The University and the College of Natural Sciences are to achieve the highest standards of faculty performance. This Centennial Professorship, together with other endowed faculty positions, makes it possible to build and to maintain a distinguished faculty dedicated to superior teaching, research, and scholarship.

William H. Cunningham, President

The University of Texas at Austin

Message from the Dean

The College of Natural Sciences and the Department of Astronomy are honored to have received the Harlan J. Smith Centennial Professorship in Astronomy. The Anonymous Donor's generosity has a profound impact on the quality of teaching and research in the College of Natural Sciences.

This Centennial Professorship affords a unique opportunity to recognize the major contributions which Harlan Smith has made to McDonald Observatory and the Department of Astronomy. The special recognition which the Professorship provides for the recipients assures attraction of preeminent astronomy scholars to the Department in future years. Endowed support, such as this, from individuals who believe in striving for the very best in research and teaching, will thus serve in turn to guarantee continued excellence in astronomy in Texas.

Robert E. Boyer, Dean

College of Natural Sciences

The First Recipient.

William H. Jefferys

Astronomy is the science of the heavens, and because of it we are able to glimpse our place in the grand scheme of the universe. William H. Jefferys, a man fascinated with astronomy since childhood, has helped define our location in the universe through investigations of the behavior of the solar system and other dynamical systems and through techniques for measuring distances to the stars and beyond.

Born in 1940 in New Bedford, Mass., Jefferys majored in astronomy at Wesleyan University in Connecticut, graduating with high honors and distinction. His astronomical contributions began in the early 1960s, while he was an undergraduate.

While at Wesleyan, and later as a graduate student at Yale, he worked in the field of astrometry with Heinrich Eichhorn. Astrometry is concerned with the motion of objects on the celestial sphere, perpendicular to our line of sight and with the determination of accurate positions for these objects.

By incorporating then-novel computer programs, Jefferys and Eichhorn developed a technique in which they overlapped photographic plates to obtain accurate positions for celestial objects. Accurate positional measurements can lead to a determination of the parallax of the object, an apparent shift in the object's position against the starry background actually caused by Earth's own movement around the sun. Stellar parallax can be obtained only for nearby stars, and gives accurate indication of the stars' distances from Earth. Once an accurate position is obtained, it becomes possible to learn whether an object shows a "proper motion," or sideways motion across the sky. A proper motion in itself does not indicate the object's distance, but it does show that the object is relatively nearby.

They were among the first to use computers in the area of photographic astrometry, and the accuracy of these techniques permitted Jefferys to make significant early contributions in determining proper motions for objects beyond our galaxy.

Jefferys turned a questioning mind toward the object called 3C273 which looked like a star on photographic plates but whose spectrum was very peculiar. While the object looked like a star, its spectrum indicated it was farther away than most galaxies known at the time. By accurately measuring the proper motion of this object with the new astrometric techniques, he was able to show that it did not appear to move, and therefore must be located far beyond the confines of our Milky Way Galaxy. Objects such as 3C273 are now called quasars and are the most distant objects known in the universe.

Harlan J. Smith, also at Yale then, had suggested to Jefferys that he look at 3C273. Later, Smith submitted Jefferys' name for the distinguished Alfred P. Sloan Fellowship, which Jefferys received as he completed his dissertation, but it was a year before he was able to take advantage of his fellowship.

At that time, Jefferys was still teaching at Wesleyan University, where Heinrich Eichhorn had been running the astrometric program. Eichhorn took a position elsewhere, and Jefferys took over his astrometric program then in its final year under a grant from the National Science Foundation.

After completing the program at Wesleyan, Jefferys directed his interest toward the "restricted three-body problem," the area which he had explored in his dissertation. This mathematical and theoretical problem models the way in which planets and stars move under the influence of gravity. The classical three-body problem is unsolvable; there is no way to write a formula describing the orbits of three interacting bodies over an indefinite period of time. It is possible, however, to look at certain aspects of the three-body problem, to explore them and gain some understanding of them without entirely solving the three-body problem. This is the restricted three-body problem which Jefferys had studied with the hope of understanding the stability and long-term behavior of the orbital motions of planets, satellites and stars.

In his dissertation, "Some Dynamical Systems of Two Degrees of Freedom in Celestial Mechanics" on some aspects of the restricted three-body problem, Jefferys used some new mathematical ideas developed by Jurgen Moser, a noted mathematician, then at New York University. Jefferys spent his Sloan Fellowship year as a postdoctoral fellow with Moser. He wrote half a dozen papers during this time, five independently and one with Moser. These were the first of many in the area of dynamical astronomy.

In 1966, Jefferys married Susan E. Wehger. Their son Mark was born in 1973, and another son Tom was born in 1976.

Also in 1966, Jefferys was lured to The University of Texas at Austin by Harlan Smith, to join an astronomy department with a rapidly developing first-class faculty. At Texas, Jefferys continued exploring dynamical systems. He applied his work not only to solar system objects, but also to galactic dynamics and to the dynamical stability of star clusters. He has a philosophical attitude toward the challenge of dynamical systems.

"The most interesting problems are always the ones that are the hardest," he said.

Jefferys also became interested in solving algebraic and calculus problems with computers. Calculations in celestial mechanics require extensive amounts of algebra. Jefferys designed a programming system, which alleviated the tedium in calculating these formulae, thus accelerating the work. This programming system, called TRIGMAN, was essentially finished by 1970. It is still used in celestial mechanics studies.

Along with J. Derral Mulholland and Peter Shelus, Jefferys began preliminary work for the Voyager missions, studying the satellites of the outer planets. He employed mathematical methods to determine the orbits of certain planets and their moons. Because it required photography of some of the satellites, the Voyager studies led Jefferys back to his interest in astrometry.

In 1978, Jefferys launched into a long-term astrometric project. He was appointed leader of the astrometric team for the 2.4 meter Hubble Space Telescope (HST). The team has overseen the design and building of the Fine Guidance Sensors on the HST and have helped supervise the overall scientific performance of the instrument.

In addition, Jefferys has been author or co-author of four books or monographs and more than 50 scientific papers. He has chaired 14 M.A. and Ph.D. committees and served on an additional 32 committees. He also designed several undergraduate astronomy courses. In 1982, Jefferys received the McDonald Observatory and Department of Astronomy Advisory Council Teaching Award. He served as Chairman of the Division on Dynamical Astronomy, American Astronomical Society, in 1981-82.

In 1982, Jefferys visited China for two months giving a series of 24 invited lectures at Peking Normal University, Nanjing University and Shanghai Astronomical Observatory. Interest in celestial mechanics is very strong in China, and Jefferys maintains contact with colleagues there as well as working with visiting Chinese astronomers when they come to Texas.

His concerns extend beyond an exchange of scientific information. "I'm a Quaker, and I guess that helps contribute to my interest in people. That's one of the reasons I'm interested in helping to build bridges with China. They are a quarter of the world's population. They need to solve tremendous problems of population pressure. One of the ways I think they can help solve their problems is through technology and science, so I think that this is a way I can contribute my little bit toward friendship and understanding between people."

Jefferys also has thoughts about what it means to be a scientist. "We're all doing the kind of work that we ourselves happen to be equipped to do, by our education, by our temperament, by our abilities. We're all in this enterprise together. In science, everybody builds on everybody else's work."

Li ZongWei of Beijing Normal University hosted Jefferys when he visited Beijing. Together with Craig Wheeler, they are studying the statistics of supernova remnants.

The Restricted Three-Body Problem

Dynamical astronomy is the study of the relationship of two or more orbiting celestial bodies and the factors that influence their orbits over time. Jefferys' interest in dynamical astronomy stemmed from his desire to study the long-term behavior of the solar system. He wanted to know: is the solar system dynamically stable? What is the origin of the Kirkwood Gaps in the asteroid belts--places in the belts where asteroids appear to be absent? Why do some objects revolve around their parent bodies in times that are simple fractions of each other?

In dynamical astronomy, the two-body problem has been solved. It is possible, for example, to calculate the orbits of the sun and one planet for an indefinite period of time. No general solution exists for triple or multiple systems; the classical three-body problem cannot be solved.

Some special cases of the "restricted" three-body problem have been solved. As early as 1772, J. L. Lagrange first offered solutions. In the restricted problem, the mass of one of the three orbiting bodies is taken to be zero. The restricted three-body problem is a step toward understanding the full three-body problem; it is a step toward understanding the behavior of dynamical systems.

One way to explore the restricted three-body problem is to look at periodic orbits in which orbiting bodies return to the place where they started. After a certain number of orbits, a body will return to the same position with the same velocity, that it had when it began. It repeats its motion over and over, always retracing the same path.

Two methods can be employed to search for periodic orbits. One method is numerical and lists periodic orbits that might exist. The other method is analytical using algebra and calculus to show that certain periodic orbits may exist.

In his dissertation, Jefferys used both methods. He searched with a computer for quasi-periodic orbits which would reveal information about the long-term behavior of the solar system. At the same time, he used the analytical method to find periodic orbits in three dimensions. Previously, the standard restricted three-body problem had modeled these orbits in only two dimensions.

The exploration of periodic orbits gives information on the behavior of dynamical systems over time. In the real solar system, all the planets and moons have non-periodic orbits, but some may have orbits close to periodic orbits, which make it possible to hypothesize how real planetary orbits interact with periodic orbits.

Jefferys used periodic orbits to explore the planet Pluto's "resonance" with the planet Neptune: why Pluto goes twice around the sun for every three orbits of Neptune. Jefferys looked for periodic orbits near Pluto's real orbit. Although he did not find one at the time, his work was later built upon by Paul Nacozy of The University of Texas Department of Aerospace Engineering. He added the effect of the planet Jupiter and was able to shift the periodic orbits closer to the real orbit of Pluto, making it possible to understand the Pluto/ Neptune resonance and how these worlds can be in their particular orbits with respect to each other.

Jefferys also looked beyond the solar system, using periodic orbits, to explore the dynamics of star clusters. Self-gravity holds a star cluster together. If there were nothing else in the universe, the stars would never leave the cluster. In the real galaxy, stars can leave the cluster and begin orbiting the galactic center. Jefferys sought to understand the stability of star clusters. The situation was analogous to that of stability of the satellite systems of some of the outer planets. Often, the outer satellites of these worlds orbit in a retrograde manner, or opposite the motion of the inner satellites in the system. Jefferys wondered if stars in clusters would have similar, retrograde orbits, and his work shows that they do. Though ground-based astronomy cannot yet reveal observational evidence for these orbits, the Hubble Space Telescope should be able to see them.

The Hubble Space Telescope will give astronomers a view billions of light years into the universe.

Astrometry and the Hubble Space Telescope

Both early and later in his career, Jefferys pursued a path divergent from that of dynamical astronomy. While an undergraduate student at Wesleyan, he began working in the area of photographic astrometry, in which photographic plates are used to find the precise positions of stars and other celestial objects. Much later, in 1978, he was made Principal Investigator, or "team leader," of the astrometry team for the Hubble Space Telescope.

The astrometry team is in charge of features of the telescope relating to the measurement of precise positions for celestial objects. The team has overseen the design and building of the HST's Fine Guidance Sensors, which allow the telescope to be accurately pointed toward objects in space, and also cause the telescope to accurately measure the positions of stars on the celestial sphere. The accuracy of positional measurements of celestial objects with the Fine Guidance Sensors is projected to be within 2/1,000 of a second of an arc. This accuracy, made possible because the HST will be above Earth's blanket of atmosphere, is approximately ten times greater than that of ground-based telescopes. Such highly accurate positions should revolutionize our knowledge of the distances to celestial objects.

Precise positions lead to increased knowledge of celestial distances through measurements of stellar parallax. Until now, parallax measurements for only a few thousand stars have been obtained. The Europeans are working to launch an astrometry satellite, called HIPPARCOS, which will increase that number to 100,000. But HIPPARCOS will measure only the brighter stars, while the Hubble Space Telescope will concentrate its astrometry efforts on fainter stars which are more significant from an astrophysical standpoint. Some stars on the HST's list are astrophysically interesting: for example, one is an x-ray source. Others, such as RR Lyrae stars, are used to calibrate distances in the universe. RR Lyrae stars vary in brightness, with typical periods of about half a day. All RR Lyrae stars are assumed to have the same intrinsic luminosity, and thus their apparent brightnesses yield their relative distances. When the true distances to RR Lyrae stars are obtained through HST's astrometry efforts, these stars will become even more useful to astronomers as tools to help measure the size and age of the observable universe.

Another goal of the HST astrometry team is to establish a "fundamental reference frame," a set of precise non-rotating coordinates for the stars. There are currently several reference frames for the stars, partly because Earth's precessional motion causes our vantage point on the star background to shift from year to year, and partly because the stars themselves really are moving through the Galaxy. Although the stars' movements appear too minute to detect with the eye alone, precise astrometric techniques reveal them. One possibility for establishing a fundamental reference frame involves using distant quasars, which are too far away to appear to move. In this way, it should be possible to construct a fundamental reference frame in which proper motions of stars can be more accurately measured.

Still another goal of the HST astrometry team is to look for planets in orbit around other stars. Astrometric techniques used from the surface of the Earth have indicated the possibility that such planets exist, but there is always room for error when peering up through Earth's turbulent atmosphere. The technique used by HST will be essentially the same as that used by ground based astronomy. HST's superior position measurements will reveal whether a star is "wiggling" around its position, indicating it is orbiting a common center of gravity with an unseen companion. In some cases, the unseen companion could be a planet. Some astronomers believe that planets beyond our solar system will be among the early discoveries of the HST.

Members of the Hubble Space Telescope astrometry team (From left to right) include Paul Hemenway, William H. Jefferys, G. Fritz Benedict, Peter J .Shelus and Raynor L. Duncombe. Not shown are non-UT members Laurence W. Fredrick (University of Virginia), Otto Franz (Lowell Observatory), and William F. van Altena (Yale University).

In much the same way, HST will be used to look at a class of double stars known as "astrometric doubles." Currently, close double stars are revealed by an analysis of their light, or spectra; wide doubles can be observed optically. There is also a gray area in which the number of double star systems is uncertain. Astrometric techniques with the HST should reveal many doubles in this gray area, giving a much more accurate count for the overall number of double systems among the stars of our galaxy.

Relativity experiments will also be conducted by HST. It will be possible to measure light from stars that pass close to Jupiter to see whether Jupiter's gravitational field bends their light the same way that the sun's gravity bends the passing light of stars.

In addition to overseeing the design and building of the Fine Guidance Sensors, and to guiding the applications of the instruments, Jefferys and others on the HST astrometry team will refine data analysis procedures. Jefferys has made a data reduction breakthrough which will be used after the telescope is launched; he developed a generalization of the method of "least squares," used by all scientists as a method of finding errors in data reduction. Jefferys' method was developed for astrometric techniques, and it will be employed when data is returned from the HST.

Astrometry--the measurement of star positions--is one of the oldest astronomical pursuits. Since the earliest stargazers looked upward and began wondering about our place in the cosmos, people have been trying to describe the dynamics of worlds in space. The work of William Jefferys has advanced the modern understanding of these two fundamental areas of astronomy. It has helped lead us toward an increased knowledge of who we are and where we are in the universe.

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