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Charlotte Moore Sitterly (1898–1990)

Published onSep 01, 1991
Charlotte Moore Sitterly (1898–1990)

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Charlotte Moore Sitterly was born in Ercildoun, Pennsylvania. Her parents were both teachers and her father was the superintendent of schools in Chester county for many years. She was the youngest of four children, one boy and three girls. She and a sister two years older were very close. Well into her eighties, Charlotte drove to Pennsylvania on many weekends to be with her sister who was then in a nursing home. Her parents' interest in education had a strong influence on the family. The children played many educational games at home. Both sisters went into teaching.

Her parents picked the nearby Swarthmore College for the birthright Friend. Charlotte remained a Friend throughout her life, although she was also an active associate member of a Methodist church to which her husband belonged. The public high school which she attended was very good, but at first she felt at a disadvantage at Swarthmore where most of the students were from private prep schools. She also felt a social stigma because she was not financially well off although many of the students who seemed to look down on her at first later became good friends.

She did both tutoring and a substantial amount of substitute teaching, from first grade through twelfth, to earn her way through college. She obtained a teaching certificate, and liked children but found teaching too wearing. Although Charlotte felt harried by having to work as well as study, she found time to belong to the glee club and the hockey team and to be active in student government for which she was treasurer.

For her first two years, she sampled a wide variety of courses, getting a good general education but missing some of the subjects such as physics and chemistry which she should have had. When she had to pick a major on very short notice at the end of her sophomore year, she had enough courses only in French and mathematics. She chose the latter, which she had always liked. She took a course in general astronomy, but no advanced astronomy.

She would have liked to go to graduate school immediately after graduating, Phi Beta Kappa, but did not get a fellowship and had to go to work instead. The head of the mathematics department was an astronomer, John Miller. He knew that Henry Norris Russell, at Princeton, was looking for an assistant and recommended her. She took the position as a computer without even an interview. (Before the advent of electronic computers, women who were general assistants in observatories, doing a wide variety of work including computing, were known as computers. I am unaware of any computers who were not women, although it is possible that a man might have taken the job occasionally. )

The job at Princeton was like being thrown into deep water. Russell was a quick and brilliant thinker. Although he did tell Charlotte how to do the various things he wanted done, his explanations were quick, leaving her to fill in many of the details and all of the background. Her work at Princeton lasted 25 years and set the pattern for the rest of her life. It may be that Dr. Miller, who was known for his research on the sun, particularly observing solar eclipses, had some role in her interest in the sun, but it was at Princeton that this interest really developed.

Although she started to work on eclipsing binaries for others in the department, computing orbits for 90 systems, she soon shifted to work only for Russell. She was the only assistant for a man who needed two or three to keep up with his wide range of interests. She supplied him with a variety of data which she collected and put into the form he needed. When he traveled abroad to meetings, she had the responsibility of preparing material for him, seeing to it that he had everything he needed, and checking his slides. She had many stories of experiences accompanying him to meetings, both in the US and abroad. On a more mundane note, she gave up using soft pencils. Russell liked soft pencils and any in his vicinity would immediately jump into his pocket. From time to time, Charlotte would collect all his pencils and return them to the observatory, providing them gradually later.

Russell encouraged her to attend the evening lectures which he gave to the graduate students. Her work prevented her from attending undergraduate lectures. Of course, as a woman, she could get no credit for any of the lectures she attended.

Her first responsibility at Princeton was measuring the position of the moon with respect to stars. This involved becoming familiar with the rough edge of the moon, estimating the proper number of spots to measure, and reducing the final data, without recourse even to a desk calculator. Since the reductions were involved, they were far from trivial to do with logarithms and hand arithmetic. Also, the measuring machine was archaic and difficult to keep working and in adjustment.

Russell was very interested in both stellar evolution and stellar abundances and Charlotte worked on both. In the early thirties, she collected all of the double star measurements she could locate in the literature and visited Lick Observatory to get Aitken's unpublished data. She then plotted all of the positions for nearly 2500 stars and from these plots, estimated the periods and the semimajor axes, and, thence, dynamical parallaxes. She also compared the spectroscopic parallaxes with trigonometric parallaxes and showed that they agreed well. Based on all of the data then available, she prepared the HR diagram, in her book with Russell on the Masses of the Stars (1940). The problem was to decide, on the basis of the literature, in what class each star should be put. Since she was inexperienced, Russell decided the difficult questions both for this and other tasks, but she did most of the work.

She also collected data on atomic spectra, leading eventually to the publication of the Mutiplet Table of Astrophysical Interest Revised in 1945. This book and its companion, the Ultraviolet Multiplet Table (1950), have served as indispensable references for stellar and solar spectroscopists ever since. At the same time she was collecting spectral data, she was using them to identify lines in the solar spectrum.

Working for Russell was strenuous, and Charlotte's health was not good. In 1925, she asked for a leave of absence. With Russell's concurrence, she spent the next three years at Mount Wilson working with St. John and Babcock on a Revised Rowland Table. She did most of the identification work and many of the intensity estimates for this revision, recalibrating the Rowland intensity scale as part of her effort.

She took advantage of Russell's two year sojourn in Europe in 1929 - 1931 to return to college for her Ph.D. She was able to get a fellowship from U. California , Berkeley and spent a year there, taking the required courses before going to Mt. Wilson where there was a great deal of data she could use for her thesis. She decided to study the atomic spectra of sunspots, feeling that the atomic lines, which were recognizable from their Zeeman behavior, would be more a manageable problem than the molecular lines. She also estimated the intensities of the lines by comparing them with the Rowland intensities for the disk spectrum.

After receiving her Ph.D., she returned to Princeton as a Research Assistant, becoming a research Associate in 1936. She kept Russell supplied with multiplet data for hundreds and hundreds of multiplets and continued to work on solar identifications. She was finally able to hire an assistant, Isabel Murray, who later joined her at the Bureau of Standards.

There was an obvious synergism between Moore and Russell. He wanted reams of data instantly; she insisted on being sure that the data were correct before she gave them to him. He jumped from one thought to another quickly; she provided the necessary stabilization of a competent, meticulous worker. The work with Russell on evolution and abundances provided the introduction to her life-long work on atomic spectra and the solar spectrum.

In 1937, Charlotte married the astronomer, Bancroft Sitterly (Banny), whom she had known since he was a graduate student at Princeton in the early 1920's. During World War II, Banny worked at MIT. Charlotte lived with him in Cambridge but commuted to Princeton to continue her work on Fe I part time.

Wm. F. Meggers had provided data on ytterbium to Russell in 1932, at which time he got to know Charlotte. He later offered the data on ionized vanadium (V II) to her (he offered the data on V I to Russell). By 1945, Russell had retired and there was no future for Charlotte at Princeton. Although, being married now, she was not looking for another job, Meggers urged her to come to the Bureau of Standards to manage the atomic spectroscopy program after Russell and Shenstone had agreed that she was the best person for the job. She was put to work almost immediately on atomic energy levels, a task in which Compton, the new director, was very interested. Asked to hire her own assistants, she hired various retired scientists who were paid little but provided competent and substantial work over the years. She also brought Russell to the Bureau as a consultant. (The idea of Russell working for her amused her!)

Banny got a job at the Naval Observatory and a little later, at American University where he became chairman of the Physics department. Unlike Charlotte, Banny loved teaching but they had many other interests in common including music and gardening. They bought a house in a quiet neighborhood in northwest Washington not far from the Bureau of Standards. Although she described the house as too small for much entertaining, it was almost a hotel for colleagues visiting Washington. A few months before her death, she mentioned that she would be having three guests for several days. She was also known for her homemade bread. When she was found after her death, fresh loaves of bread were on the table.

Charlotte not only gathered all of the data she could find on atomic spectra from the literature, she also begged the unpublished data of which she was aware. When gaps still remained, she determined who could best fill the gap and convinced that person to provide the necessary data. Her ability to collect unpublished data and to get spectroscopists to provide new data illustrates the esteem in which she was held by the community. Although she published more than 100 papers after 1945, she is best known for the three volumes of Atomic Energy Levels (1949-1958) and her multiplet tables.

She took the job at the Bureau of Standards only after being promised that she could continue to work on the solar spectrum, at that time, a study with Babcock of the infrared spectrum. That the pressure of the spectroscopic work forced her to do the solar research on the side did not deter her. She was also very interested in the XUV spectrum, although she never expected to see it. It is in this region that the ultimate lines of many common elements are found. She was ecstatic when she read of the XUV spectrum of the sun which Tousey had obtained during a rocket flight. She immediately asked to work on it with him. She continued her association with the Naval Research Laboratory and Tousey until her death, even though in later years it meant a long walk and at least a ninety minute bus ride each way. She was forced to retire in 1968 at the age of 70, but maintained an office at the Bureau and continued to work there regularly, even after the Bureau moved to Gaithersburg, more than 25 miles from her home. In her late eighties, she complained of the many requests for data she received and how little some of the requesters understood the magnitude of the effort required, but she continued to respond.

During her activity at the Bureau, she served the community in many other organizations. She was vice president of the American Astronomical Society and of section D of the AAAS, and president of the commission on Fundamental Spectroscopic Data of the International Astronomical Union. She also served on the Scientific Manpower Commission, the National Research Council committee on Line Spectra of the Elements, the International Commission of Scientific Unions committees on Spectra and on Scientific and Technical Data, and the International Union of Pure and Applied Physics Triple Union Commission on Spectroscopy.

Her highly respected work brought her many honors. In 1937, she received the Cannon prize which, at that time, the AAS awarded for an extensive period of outstanding work. In 1949, she became the first woman to be appointed an Associate of the Royal Astronomical Society. She was one of the first six recipients of the Federal Women's Award, in 1961, as an outstanding woman in government. The six women from widely varied fields became close friends and continued their association until their deaths. The Astronomical Society of the Pacific awarded her their Bruce medal for a lifetime of achievement in astronomy posthumously in 1990 but she knew of the award before her death. She received honorary degrees from Swarthmore College and the Universities of Michigan, Kiel (Germany), and Georgetown. Other awards included both the Silver and the Gold Medals of the U.S. Department of Commerce, the Cannon Centennial Medal of Wellesley College, the National Civil Service League Award (rarely given to a woman at that time), and the William F. Meggers Award of the Optical Society of America. She was a Fellow of the American Physical Society and the Optical Society of America and an honorary member of the Society for Applied Spectroscopy.

Dr. Sitterly's books had an enormous influence, not only in astronomy but also in chemistry, and plasma and laser physics. Little of her work has been superseded. In spite of her outstanding recognition, she remained humble with a sincere concern for others and a desire to serve. She was a wonderful raconteur and a delightful person to be with.

I thank the Niels Bohr Library of the American Institute of Physics for the loan of the transcript of an interview with Dr. Sitterly conducted by Dr. DeVorkin in 1978 and Dr. Elizabeth O'Hern for the provision of a prepublication copy of the chapter on Dr. Sitterly in her book on Women in Astronomy.

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