Bowen, Ira Sprague, 1898-1973

Ira Sprague Bowen (1898-1973), a physicist by training, was the third Director of the Mount Wilson Observatory from 1946-1964.

Astrophysicist. California Institute of Technology.

Biography

One of the most distinguished astrophysicists of the twentieth century, Ira Sprague Bowen made fundamental contributions to the analysis of atomic spectra, the physics of gaseous nebulae and practical optics. Born in Seneca Falls, New York, in 1898, he graduated from Oberlin College in 1919 before entering the University of Chicago. There, he studied with Albert Michelson who infused in Bowen a love of optics. He also met Robert A. Millikan, who invited him to the California Institute of Technology in 1921.

By 1926 Bowen had received his doctorate from the institute and was appointed an assistant professor at Caltech. Soon after he made his first outstanding discovery: the identification of the so-called nebulium lines in the spectra of gaseous nebulae. The following decade, Bowen built an innovative device, called an image slicer, which placed the spectra of successive strips across an extended object, side by side upon a photographic plate. This invention enormously increased the efficiency of observations of gaseous nebulae and he received international attention when he provided an explanation for lines appearing in the spectra of planetary nebulae. During World War II he participated in the Caltech ordnance rocket project, developing the use of high-speed cameras in rocket design. Following the Second World War, he continued to research nebulae in collaboration with Rudolf Minkowski and published many significant papers on the subject.

Upon the retirement of Walter Adams, Bowen assumed the directorship of the Mount Wilson Observatory and, in 1948, the combined Mt. Wilson and Palomar venture. Despite his administrative duties, he continued to make significant contributions to optics, even following his retirement in 1964.

Bowen received many honors. He was a Gold Medallist and Halley lecturer of the Royal Astronomical Society. Among the other medals he received were the Ives (Optical Society of America), Draper (National Academy of Sciences), Potts (Franklin Institute), Rumford (American Academy of Arts and Sciences) and Bruce (Astronomical Society of the Pacific). He was a member of the National Academy of Sciences, the Royal Swedish Academy of Sciences and the Indian Academy of Sciences.

Biography

Ira Sprague Bowen, a physicist by training, was the third director of the Mount Wilson Observatory. As director, he led the Observatory through its biggest transition since its founding in 1904: its joint operation of the largest telescope in the world, the 200-inch Hale Telescope, with the California Institute of Technology. Even though his formal scientific output fell off as director, his position of responsibility for the Mount Wilson and Palomar Observatories marks him as a very important figure in the history of American science.

Ira Bowen was born on December 21, 1898, in Seneca Falls, New York. His father, James H. Bowen, was pastor of the local Wesleyan Methodist Church. His mother, Philinda Sprague Bowen, was a licensed teacher in New York State. In 1900, the family moved to Millview, Pennsylvania, and five years later James Bowen became business agent of the Wesleyan Methodist Church. This latter position resulted in the family moving around quite a bit when Ira Bowen was still very young, and he was educated at home until 1908. In 1908, James Bowen died, and Ira entered the Houghton Wesleyan Methodist Seminary where his mother had become a teacher.

Ira Bowen's interest in science grew during his stay at Houghton where he became adept at devising many experimental arrangements with the limited resources of the school and his family. He stayed on to attend the junior college at the seminary and he was placed in charge of the high school physics laboratory. After three years of college courses at Houghton, Bowen transferred to Oberlin College for his senior year, receiving his A.B. degree in 1919.

Bowen's aptitude for research was quickly recognized and in the fall of 1919 he was given a scholarship and began to pursue his graduate studies at the University of Chicago. He soon took the vacant position as laboratory assistant to the eminent physicist Robert A. Millikan, a figure who became a tremendous influence on Bowen. Under Millikan, Bowen gained expertise in spectroscopy and atomic physics.

In 1921, Millikan was tempted by George Ellery Hale to transfer to the new California Institute of Technology (Caltech). Bowen accompanied Millikan and became a lecturer in the physics department while assisting Millikan in his cosmic-ray research. In addition, Bowen also found time to continue his own atomic physics research, especially in the fields of vacuum ultraviolet and x-ray spectroscopy.

Bowen did not obtain his Ph.D. degree until 1926, mainly because of his heavy research and teaching load. The future importance of the degree finally caused him to take it with a thesis on a project alien to his main interests. While guiding a student on a project dealing with evaporation, the student lost interest, but Bowen maintained his own excitement and completed the research. Since he was working on the evaporation project when he decided to take his degree, he used this research, "The Ratio of Heat Losses by Conduction and by Evaporation from Any Water Surface," as his thesis.

Bowen's entry into the astrophysical world came when he read about the dilemma of the "nebulium" lines. Since the 1860's astronomers had been unable to identify many of the emission lines in the spectra of galactic nebulae. As a result they postulated the existence of an element, "nebulium," unknown on earth, which produced the mysterious spectral lines. For various reasons, the nebulium explanation was unsatisfactory and astronomers continued to search for a better answer. In 1927, after reading a possible explanation advanced by Henry Norris Russell, Bowen realized that the nebulium lines could be explained by electron transitions that were only possible in a rarefied gas. The nebulium lines would never have been observed on earth since no gas was rarefied enough to prevent electron collisions from interfering with the infrequent transitions which produced the lines. Since Bowen had the necessary spectroscopic data on hand from his earlier research, he quickly calculated the wavelengths of the spectral lines of these "forbidden" transitions of various light elements. After obtaining the wavelengths, he compared them to those of the nebulium lines and saw that they were indeed the same. Bowen's reputation in astrophysics was made and he now had a new field in which to turn his tireless research activities.

It was during this new burst of activity that Bowen married Mary Jane Howard in 1929. No personal letters exist in this collection, but that is not surprising since they were very rarely separated. Mary Bowen's position as a child psychologist often prevented her from going with Ira on his journeys to Washington, D.C. for Carnegie Institution of Washington (CIW) meetings or other astronomical council meetings, but these trips were of short duration. They had no children.

Although Bowen continued with his laboratory spectroscopy and cosmic-ray work, he fell deeper into astrophysics. Collaborations with William Hammond Wright at the Lick Observatory led to his appointment in 1938 as Morrison Research Associate. During his summer at Lick, he worked with Arthur B. Wyse on the study of the spectra of galactic nebulae. Due to the difficulty of taking spectra of the faint nebulae, Bowen developed the "image slicer," a device that essentially enabled more of the light of the target nebula to enter the narrow spectrograph slit. This keen aptitude for instrumentation and optics would prove invaluable in the development of observational astronomy.

Bowen soon got a chance to apply his expert knowledge of optics when he was placed on the Policy Committee of the 200-inch telescope. The 200-inch project got underway in 1928 when George Ellery Hale obtained funding from the Rockefeller Foundation to build the world's largest telescope. During the 1930s Bowen played an important part in many of the design decisions for this enormous undertaking. He did not realize that he would eventually be the central figure in the telescope's completion.

His involvement with the 200-inch telescope had to be put aside during the Second World War. As did most scientists, Bowen joined the war effort by signing on with the Caltech ordnance rocket project, where he found himself working alongside many of the Mount Wilson astronomers. Until 1945, he helped in the research on all aspects of rocketry as well as producing a high-speed camera and taking part in studies on the transparency of seawater. He was also appointed a project supervisor of several Office of Scientific Research and Development contracts on the West Coast. One of these was the contract that involved the Mt. Wilson Observatory in war work.

The turning point in Bowen's career came in July, 1945, as the War was coming to an end. Vannevar Bush, head of the Office of Scientific Research and Development and president of the CIW, informed Bowen that he had been chosen to be the new director of the CIW's Mount Wilson Observatory. The Observatory's second director, Walter Sydney Adams, was retiring on January 1, 1946, and in the discussions concerning his successor, Bowen's name had come up practically from the start. His familiarity with the Mount Wilson staff and his optical/instrumental expertise made him an obvious choice as director. Bowen soon accepted the offer and began to make the transition from researcher to administrator.

Bowen's main task as director was the completion of the 200-inch telescope to be placed on Palomar Mountain. The funding for the telescope had been given to Caltech, but they did not have the staff to operate the Palomar Observatory. The decision was made that the Mount Wilson Observatory would operate the Palomar Observatory as well, but under the joint administration of Caltech and CIW. As director, Bowen would have to deal effectively with both CIW and Caltech, a job he performed exceedingly well during his eighteen-year tenure. In 1946, when he came on board as Observatory director, the 200-inch was four years away from completion. With most of the original designers retired or ill, Bowen, with the able assistance of Bruce H. Rule, took personal charge of the final stages of the project. In addition, he oversaw the staffing and organization of the Palomar Observatory. Realizing the magnitude of the project, Bowen took little time out for other affairs until the 200-inch mirror had been polished and figured. He personally analyzed the optical tests of the mirror. The 200-inch telescope was dedicated in June 1948 as the Hale Telescope, but Bowen continued to concentrate on the mirror until the telescope was placed into regular service in 1949.

With the dedication of the 200-inch Hale Telescope in 1948, the Mount Wilson Observatory became the Mount Wilson and Palomar Observatories [MWPO]. Along with the 60-inch and 100-inch telescopes on Mount Wilson, Bowen was in charge of the most awesome telescopic array in the world. Understanding that many astronomers, especially those on the American East Coast and Europe, had rare access to instruments such as those at MWPO, he developed the guest investigator program. Although he could not meet the needs of all astronomers, the guest investigator program helped enrich many research programs before the existence of "national observatories."

Joining the excellent instruments of the MWPO was the new 48-inch Schmidt telescope on Palomar. This telescope, with its extremely wide field of view and high speed, would open a new vista for astronomical research. Bowen knew that the best initial use for the Schmidt telescope was a photographic survey of the entire sky visible from Palomar. Funding for this massive project was provided by the National Geographic Society and it got underway in 1949. Supervised by Rudolph Minkowski, and photographed by Albert G. Wilson and George O. Abell, the National Geographic Society-Palomar Sky Survey consisted of approximately 2000 photographic plates. These plates would be copied and then sold at cost to any astronomical institution desiring a set. Completed in 1957, the Sky Survey has proven to be an essential tool in the study of all facets of astronomy.

The period when Bowen was director was a time of great change for science. New funding structures were put into place for "big science" with the continued interest of the military and the new National Science Foundation. Bowen's advice was sought out by many to aid in the establishment of post-war institutions and research. His expertise in optics also made him a great resource for those designing the latest telescopes. Among these were Vannevar Bush, Theodore Dunham, Jr., and Robert R. McMath. The latter found Bowen's counsel invaluable for the development of AURA, Inc., and the Kitt Peak National Observatory.

Bowen's directorship ended in 1964, at the mandatory retirement age of 65. Nevertheless, he continued his close relationship with the Observatory as Distinguished Service Staff Member, Carnegie Institution of Washington. In this capacity he helped develop innovative optical designs on three new telescopes, the 60-inch at Palomar, the 40-inch Swope Telescope, and the 100-inch Irenie DuPont Telescope, the latter two at Las Campanas. He was also highly sought after as an optical consultant for the development of the new large telescopes which were springing up all over the world, to the point of even being offered a senior professorship at the University of Arizona.

Throughout his career, Bowen was recognized as an important contributor to science. His peers conferred many awards on him including the Draper Medal (National Academy of Sciences, 1942), the Rumford Premium (American Academy of Arts and Sciences, 1949), the Ives Medal (Optical Society of America, 1952), the Bruce Gold Medal (Astronomical Society of the Pacific, 1957), and the Gold Medal of the Royal Astronomical Society (1966).

Bowen's life ended suddenly on February 6, 1973, while he was working on designs of the DuPont Telescope. To describe Ira Bowen, it would be best to rely on the testimony of his close associates. Jesse Greenstein, chairman of Caltech's astronomy department during Bowen's tenure at MWPO found it "hard to communicate his personal charm. He was a modest and reserved man at all times, 'Ike' to everyone. He had many of the virtues of the past generation that built science in the United States. His background, his long, happy marriage to Mary Jane Howard, his love of the outdoors, small animals, photography, hiking in the mountains, his personal and scientific economy lent him assurance and gentleness." And his long-time associate at MWPO, Olin Wilson, said of Bowen that he "was a rather reserved individual whom many people found difficult to know well. His great enthusiasm for his work is shown by his many accomplishments, yet it never appeared on the surface as exuberance. His great strength lay in careful, logical thinking through of problems before arriving at solutions. Consequently, everything he designed worked exactly as he said it would. There can be no question that he is one of the major figures in the astronomy of the 20th century."