(b. Kharkov, Russia, 12 August 1897; d. Berkeley, California, 6 April 1963)
Struve was the son of Gustav Wilhelm Ludwig Struve, professor of astronomy and geodesy and director of the observatory at the University of Kharkov. He graduated from the Kharkov Gymnasium with honors in 1914, then entered the university. His studies were interrupted by World War I, and on his father’s advice he went to Petrograd in 1915 to enroll in artillery school. He was sent to the Turkish front as a junior officer in the following year. When Russia withdrew from the war in 1918, Struve returned to Kharkov to resume his education, and soon caught up with his former classmates to take a first-class degree in astronomy. He became an instructor at the university, but when civil war broke out in Russia was recalled into the army under General Denikin, who was then retreating before the advancing Red Army.
In 1920 Struve was evacuated from the Crimea, along with the remnants of Denikin’s army, and placed on a ship full of starving and dysentery-ridden refugees; no country would admit them, but Turkey allowed them a small territory in which the emigrants lived in tents during the winter of 1920–1921. Struve went to Constantinople in spring of the latter year, but was unable to find housing or employment, since the city was crowded with Russian emigrants.
While in Turkey, Struve, seeking news of his relatives in Russia, wrote to his uncle Georg Hermann Otto Struve, who was then in Berlin. Hermann Struve had died, but his widow wrote to his colleagues of their nephew’s plight, and E. B. Frost, director of the Yerkes Observatory in Williams Bay, Wisconsin, invited him to come to the United States as an assistant observer in stellar spectroscopy. After surmounting considerable difficulties–he had no money and no visa–Struve left Turkey and reached Yerkes in November 1921. On Frost’s advice, he immediately began spectral investigations of stars and continued his studies and improved his English. In 1923 he received the Ph.D. from the University of Chicago and in the following year became an instructor at the observatory. In 1927 he became an American citizen.
Struve quickly rose to prominence at Yerkes, becoming assistant professor in 1927, associate professor in 1930, assistant director in 1931, and, on Frost’s retirement, director in 1932. He held the last post until 1947, when he became chairman and honorary director, a position he held until 1950. From 1932 until 1947 he also served as professor of astrophysics at the University of Chicago, which administered Yerkes.
Struve was also concerned with the founding of the McDonald Observatory in Texas. As he himself recounted, in an article published in Sky and Telescope (volume 24 , 316–317),
After becoming a staff member at Yerkes Observatory in 1921, I was most closely associated with George Van Biesbroeck. Together we determined many comet and asteroid positions with the 24-inch reflector. … But my main task was observing the spectra of B and A stars, following a program prepared by Director Edwin B. Frost. … It soon became apparent to Van Biesbroeck and me that very faint asteroids and comets could not be observed with the 24-inch. I also realized that the Bruce spectrograph was not suitable for medium or high-dispersion spectra of stars. . . . No wonder Van Biesbroeck and I spent many cloudy night hours trying to think how we could secure a moderately large reflector, preferably in some other location that had more clear nights. . . . Since we were thinking of a small observing station, equipped with a 60-inch telescope and operated from Yerkes, we wanted it to be not too far from headquarters. We consulted weather data, and noted a good location in the high plains of the Texas Panhandle, near Amarillo.
These plans were not immediately implemented, and it was only in 1932, after Struve had been invited to become assistant director of the Harvard Observatory, that the officials of the University of Chicago decided to offer him what he wanted. Struve became Yerkes’ director in the same year, and the university appropriated $15,000 toward a new observatory–far less than the required amount.
The situation was soon resolved, however. A few years earlier, a banker from Paris, Texas, had left $800,000 to the state university at Austin to build and equip a new observatory; his will was contested in the courts for six years, but the money was available to the university by 1932, and Struve, who knew of the bequest, persuaded Robert M. Hutchins, president of the University of Chicago, to meet with the president of the University of Texas to discuss the construction of an observatory in common. “Within ten minutes,” according to Struve, “the two university presidents had agreed upon a broad plan of cooperation, whereby Texas would pay for the telescope and retain ownership of it, while Chicago would pay all salaries and most of the operating expenses.” Struve himself was to be director of the new observatory, and in the summer of the same year he took part in selecting a site on top of a double hill (named Mt. Locke, after the donor of the land) in west Texas. He immediately began writing to the directors of other large observatories, soliciting their suggestions, and to telescope-makers, asking for bids and proposals.
By 1936 the eighty-two-inch telescope, then the second-largest in the world, was nearly completed; Struve had assembled most of his staff, including C. T. Elvey, W. W. Morgan, G. P. Kuiper, P. Swings, B. G. D. Stroömgren, S. Chandrasekhar, and J. L. Greenstein. The observatory was dedicated on 5 May 1939, although a good deal of work was already under way there. Struve remained as its director until 1947, at which time he became honorary director and chairman of the astrophysics department, positions that he held for another two years. In the years just after World War II, he was able to recruit a number of distinguished European scientists, to whom he offered professorships at McDonald or Yerkes.
In 1950 Struve had begun to suffer from overwork and insomnia, and left McDonald and Yerkes to accept a less demanding appointment as head of the department of astronomy at the University of California at Berkeley, and director of its affiliated Leuschner Observatory. He proved to be a gifted teacher, especially of graduate students, and was able to continue his own research, including projects as a guest investigator at Mt. Wilson. He missed the autonomy and the direct access to the president he had had at Yerkes, however, and in 1959 he returned to that institution. In the same year he was offered the post of director of the new National Radio Astronomical Observatory, which was nearly completed at Green Bank, West Virginia, with its giant eighty-five-foot radio telescope. He took the job willingly, in part from a sense of moral obligation–he had himself written of the need to accept “those laborious and often thankless jobs that are needed for the general advancement of science.” Within three years he had made the observatory, despite its geographic isolation, a first-rate scientific institution, staffed by a loyal and dedicated group of young scientists.
By 1962, Struve’s health forced him to resign from the new observatory, but he was unable to remain idle for long, and soon accepted a joint professorship at the Institute of Advanced Study, Princeton, and the California Institute of Technology. He died soon after, survived by his mother, who had followed him to the United States in 1923, and by his wife, Mary Martha Lanning, a singer whom he had married in 1925. They had no children.
Although much of Struve’s career was devoted to organization and administration, he nevertheless found time to conduct his own investigations. T.G.Cowling, in the memorial sketch of Struve published in the Biographical Memoirs of Fellows of the Royal Society, cites Swing’s account of Struve’s demanding schedule;
While at Yerkes he used to start very early in morning, finish late and take hardly any time for his meals. At McDonald he could relax somewhat from his administration duties, hence was eager to spend as much time as possible at the telescope. He loved challenges, physical as well as intellectual, and I have often seen him actively measuring at the microscope after only a few hours’ sleep following a long winter night at the 82-inch. Occasionally he would drive from Williams Bay to Chicago in the morning, fly from Chicago to Big Spring [Texas], drive then (over 200 miles) to McDonald, and be ready for a whole night’s work at the 82-inch.
Struve’s chief astronomical and astrophysical interests lay in spectroscopic investigations of binary and variable stars and researches into stellar atmospheres, stellar rotation, the gaseous constituents of cosmic matter, and stellar evolution. The nature of his work was strongly influenced by Henry Norris Russell, and particularly by Russell’s “Some Problems of Sidereal Astronomy,” published in 1919. As Struve later wrote (in “The General Needs of Astronomy”), “My own work in astrophysics was stimulated and directed by this article, and even today  it forms one of the most inspiring pieces of astronomical literature.”
Struve’s work in stellar spectroscopy was based upon protracted observations of minute changes in stellar spectra–widened and shifted lines, distortions of their contours, variations in linear intensities, the appearance of new lines and absorption bands and the disappearance of existing ones. From these observations he was able to derive a great number of spectral regularities and to point out the exceptional usefulness of the technique. He himself provided the means for further exploitation of the method by developing a means for obtaining wide-scale images of the spectra; he also, with Elvey, invented a nebular spectrograph that allows the photographic magnification of the contrast lines of weak diffuse nebulae, the spectra of which are not normally visible against the sky.
Struve investigated the gaseous constituents of cosmic matter throughout his career. As early as 1925 he showed that the stationary interstellar lines of calcium, which had been discovered by Henry Plaskett in the preceding year, are created by absorption in the extended gas clouds that are concentrated in the plane of the Milky Way. He demonstrated that these lines become more intense with distance, and, in the 1930’s, working in collaboration with B. P. Gerasimovich, found the value for the density of the interstellar gaseous substratum to be 10–26 g./cm.3, and its total mass to represent less than one percent of the complete stellar mass per unit of volume. In 1938, using his nebular spectrograph (which had been installed in both the Yerkes and McDonald observatories), Struve discovered the presence of areas of ionized hydrogen in interstellar space, a discovery crucial to modern radio astronomy. He also did research on the influence upon stellar spectra of the physical processes occurring in the stellar atmospheres, and used the division of separate spectral lines to determine that intermolecular electric fields act within the atmosphere of type A and B hot stars, and that gas turbulence also occurs there.
In 1928, in collaboration with G. A. Shayn, Struve confirmed the axial rotation of single stars that had been suggested as early as the time of Galileo. With Elvey, he investigated the rotation of several thousand stars, and established the relationship between the velocity of stellar rotation and spectral type. He paid particular attention to stars that exhibit an irregular variation in brightness, and attributed their instability to physical processes (for example, flashes, ejection of matter, or pulsation) occurring in either the stars themselves or in their surrounding atmospheres; he further maintained that the rapid rotation (more than 3,000 km./sec.) of certain extremely hot stars produces the effect that a fraction of the stellar atmosphere is thrown by centrifugal force toward the equator of the star. This condition might be expected to produce gaseous rings, and Struve discovered such rings for some stars in 1931. He then, from 1939 until 1949, made a series of meticulous studies of the formation of the gaseous ring around Pleione, in the Pleiades, and was able to detect its pulsation and rapid scattering.
Like his forebears, Struve was interested in double stars; indeed, his first scientific publication, in 1923, was an article “On the Double Star 9 Argus.” It contained a considerable amount of data on the masses of components of this visually and spectroscopically binary star; two other articles published by Struve in the following year were devoted to the orbit of the spectroscopically binary star of 43 Orionis and to the nature of binary stars of short period. In an article published in 1927 in the Russian journal Mirovedenie, Struve noted the time and effort required in observing binary stars, but went on to emphasize the value of such observations. By 1944, he was able to determine the statistical dependence between the periodicity and amplitude of the curve of distribution of line-of-sight velocity of 144 spectroscopically binary stars with periods of longer than 2.4 days. From these data Struve estimated the mean value of the stellar masses to be equivalent to about three solar masses, and he deduced a criterion for distinguishing RR Lyrae variable stars from true binary stars. He also made a study of close pairs and noted that the components of these unstable binary systems are elliptical in shape because of their mutual gravitation.
In his investigations of β Lyrae, Struve found it to be a closely paired, eclipsing binary system composed of a massive, hot, rapidly rotating blue giant and its smaller, cooler yellow satellite, in which the flow of gas from the hotter to the cooler body surrounds the stars in a kind of circular envelope that extends into space and is partially dispersed there. In a more general investigation conducted with Su-Shu Huang, Struve concluded that the formation of binary stars is accompanied by a partial loss of mass by the parent body and by an exchange of mass and momentum. His observations of close pairs and irregular stars gave him considerable insight into nonstationary star processes and provided him an approach to problems of stellar evolution, an approach that he characterized in the preface to his Stellar Evolution of 1950:
The purpose of observational research in astrophysics is to present a unified picture of a series of phenomena and to explain it in terms of a theory or hypothesis. The temptation is always to accumulate more and more factual data and to delay the process of interpretation because we rarely, if ever, feel satisfied that we have enough information to justify a generalization.... The Vanuxem Lectures at Princeton in 1949 presented a favorable occasion for taking stock in one field of astrophysics–that of the origin and evolution of single stars and, more especially, of close double stars. This subject has been treated before by other workers, but since their observational basis was different from mine I thought that it would be interesting to present this subject in the light of my own experience at the telescope.... I am, however, conscious of the fact that of necessity there is a great deal of speculation in any attempt to discuss the evolution of the star.… The history of previous evolutionary hypotheses teaches us that most of them were wrong. Yet, they have contributed to our understanding of the universe and have, in almost every case, left a permanent imprint upon later hypotheses.
Although Struve’s general hypothesis of stellar formation was not widely accepted, a number of aspects of his supporting research were greeted enthusiastically by his fellow astronomers. In particular, his demonstration of the interdependence of the velocity of stellar rotation and other stellar features–especially the positions of stars on the Hertzsprung-Russell diagram—and his detection of a correlation between speed of rotation and the distribution of stars within a cluster, the latter being an indication of the age of these stars, provided astrophysicists with the suggestion that rapid stellar velocities represent the residual motions of the turbulent vortices within the condensing diffuse medium from which the stars had arisen.
Struve was always glad to share his results with fellow workers. He considered international cooperation a necessity, since astronomy is a science of global scope, dependent upon observations made from all over the earth. In a presidential speech before the Dublin meeting of the International Astronomical Union, Struve in 1955 emphasized the problems of the development of an astronomy that would be practical for the launching of man-made satellites and space journeys. He pointed out the growing importance of sophisticated astronomical instrumentation and technology, but maintained that the most important tools of the science are the astronomers themselves.
Struve was also concerned with popularization and with communication among astronomers. From 1932 until 1947 he served as editor-in-chief of the Astrophysical Journal, and for more than forty years, from 1923 to 1963, was one of its most prolific authors as well. Between 1949 and 1963 Struve wrote an additional 152 articles (of which fourteen were published in two successive issues) for the more popular Sky and Telescope. He there demonstrated his ability to present complicated concepts of astrophysics so as to make them clear to the lay reader–although his pieces were also of interest to professional astronomers. A number of these writings were devoted to the history of science, a bent also apparent in Stellar Evolution and in Astronomy of the Twentieth Century (1962); and a number concerned the lives and careers of fellow scientists, including E. E. Barnard, the astronomer Charles Darwin, G. A. Shayn, and M. A. Kovalsky. (It may be noted that Struve was careful to acknowledge the work of his colleagues and to assign it its proper value; in particular he considered Barnard, an astronomer who worked at Yerkes until his death in 1923, as “the most capable and productive astronomical observer in the world.”)
For several years Struve edited articles and compiled abstracts for Astronomical Newsletter. He was especially concerned with Russian works, since he always took a keen interest in developments there, and was vigorous in expounding Russian research.
Struve participated in the activities of many scientific institutions and societies. In addition to the International Astronomical Union, of which he was elected vice-president in 1948 and president in 1952, he held prominent posts in the National Academy of Science, the American Astronomical Society, the American Philosophical Society, and the National Scientific Council. He was a member of the Royal Astronomical Society of London, the Royal Astronomical Society of Canada, the Royal Astronomical Society of New Zealand, and the academies of science of Denmark, Amsterdam, Norway, Sweden, Belgium, and France. He received honorary doctorates from more than ten universities.
In 1944 the Royal Astronomical Society of London gave Struve its highest award, the Gold Medal; he was the fourth member of his family to win it in some 118 years. In presenting the medal, the Society’s president, E. A. Milne, noted that the awards council had been “totally uninfluenced by the glamour that surrounds the name Struve. . . . Professor Otto Struve. . . has earned this distinction in his proper right, by the overwhelming significance and value of his brilliant observational and interpretational work in stellar and nebular spectroscopy.”
I. Original Works. The most complete bibliography of Struve’s writings (six books and 446 articles) follows A. Unsöld’s obituary in Mitteilungen der Astronomischen Gesellschaft (1963), 11–22; it does not, however, include Struve’s more than 180 popular scientific articles in Sky and Telescope, 6–25 (1946–1963) and Popular Astronomy, 32–59 (1924–1951), or his 45 book reviews in Astrophysical Journal, 60–110 (1924–1949). His books are Stellar Evolution. An Exploration From the Observatory (Princeton, 1950); The Astronomical Universe (Eugene, Ore., 1958); Elementary Astronomy (New York, 1959), written with B. Lynds and H. Pillans; The Universe (Cambridge, Mass., 1961); Astronomy of the Twentieth Century (New York–London, 1962), written with V. Zebergs; and Stellar Spectroscopy, 2 vols. (Trieste, 1969–1970), written with M. Hack.
II. Secondary Literature. There are notices and obituaries on Struve by B. V. Kukarin and P. G. Kulikovsky, in Astronomicheskii zhurnal, 40 , no. 6 (1963), 1126–1129; G. J. Odgers, in Journal of the Royal Astronomical Society of Canada, 57 , no. 4 (1963), 170–172; C. Payne-Gaposchkin, in Sky and Telescope, 25, no. 6 (1963), 308–310; J. Sahade, in Ciencia e investigacióm,19 (1963), 195–198; S. Chandrasekhar, in Astrophysical Journal, 139 , no. 2 (1964), 423; T. G. Cowling, in Biographical Memoirs of Fellows of the Royal Society, 10 (1964), 283–304; L. Goldberg, in Quarterly Journal of the Royal Astronomical Society, 5 , no. 3 (1964), 284–290; and P. Swings, in Bulletin de l’Académie r. de Belgique. Classe des sciences, 5th ser., 49 no. 6 (1964), 523–524.
Other sources on Struve’s life and work (listed chronologically) are E. A. Milne, “Address, Delivered. . . on the Award of the Gold Medal to Professor Otto Struve,” in Monthly Notices of the Royal Astronomical Society, 104 , no. 2 (1944), 112–120; A. I. Eremeeva, “Otto Ludwig Struve,” in Vydayushchiesya astronomy mira (“The World’s Leading Astronomers”; Moscow, 1966), 348–357: M. Hack, ed., Modern Astrophysics(Paris–New York, 1967), a memorial volume of collected works dedicated to Struve; P. G. Kulikovsky, O. Struve i V. Zebergs, Astronomia XX veka (“. . . Twentieth-Century Astronomy”; Moscow, 1968), 5–11; and G. H. Herbig, ed., Spectroscopic Astrophysics. An Assessment of the Contribution of Otto Struve (Berkeley, Calif., 1970).
Z. K. Sokolovskaya