GREENSTEIN, JESSE LEONARD

(b. Brooklyn, New York, 15 October 1909; d. Arcadia, California, 21 October 2002),astronomy, astrophysics.

Greenstein was an American astronomer and astrophysicist noted for his research on stellar abundances and white dwarfs, his role in helping discover quasi-stellar objects (quasars), and his directorship of the astronomy program at the California Institute of Technology (Caltech) from 1948 until 1973. He was also one of the major leaders of the post–World War II astronomy community, both internationally and in the United States, and helped shape the organization of astronomy in the United States.

Early Life and Education . Greenstein was born in 1909, the grandson of Russian émigrés. His family of cultured, wealthy, and nonobservant Jews ran a furniture-making business. Greenstein’s early years were pleasant, lacking— as he once put it—the “oft-quoted advantage of an impoverished and embittered childhood.” Greenstein developed an interest in science at a young age after his grandfather gave him a small brass telescope. As a teen he did elementary spectroscopy experiments, built crystal radio sets in his parents’ basement, and displayed enthusiasm for chemistry. His scientific career would eventually combine elements of all of these childhood hobbies.

After attending the Horace Mann School for Boys, Greenstein entered Harvard University at age fifteen, where he took courses in both astronomy and physics. Education in astronomy at Harvard at this time was still based on the positions and motions of celestial bodies and Greenstein learned about traditional topics such as celestial mechanics. He was also exposed to more modern topics in stellar astronomy and astrophysics and took courses in the relatively new field of quantum mechanics. During his undergraduate time at Harvard Greenstein met Naomi Kitay, whom he later married in 1934.

Greenstein received his AB in 1929, after which Oxford University offered him a postgraduate position. However, the Great Depression hit Greenstein’s family hard and he was forced to postpone formal training in astronomy. For several years he worked for his family in the real estate business, but kept active in research by volunteering for Isidor I. Rabi, a future Nobel Prize winner, at Columbia University. By 1934, his family’s finances had recovered and Greenstein returned to Harvard.

During Greenstein’s absence, the school had added new faculty such as Donald Howard Menzel, Fred Lawrence Whipple, and Bart Bok. These scientists helped modernize Harvard’s research and teaching profile in astronomy. Greenstein quickly completed his PhD and graduated in 1937. His dissertation research harkened back to an interest he had nurtured from his undergraduate years: the influence of interstellar dust on the color and magnitude of certain classes of stars. Greenstein, along with Whipple, had also taken notice of Karl Jansky’s discovery of cosmic static coming from the central galactic bulge. While their explanation of the phenomenon— that it might be due to thermal emission from dust clouds at the galactic center—was incomplete and overly simplified, Greenstein’s work marked his early interest in the nascent field of radio astronomy.

Yerkes Observatory . After completing his PhD, Greenstein obtained a prestigious National Research Council Fellowship for 1937 to 1939. Permitted to choose where he wished to spend his time, Greenstein picked Yerkes Observatory. Located in Williams Bay, Wisconsin, and operated by the University of Chicago, Yerkes was one of the world’s premiere institutions for astronomy at this time. Astronomers at Yerkes had access to several large telescopes including the world’s largest refractor and an 82-inch instrument (in 1939, the world’s second-largest reflecting telescope) that was nearing completion at McDonald Observatory near Austin, Texas. Greenstein thrived at Yerkes, doing both theoretical research and nighttime observing. He also learned the craft of spectroscopy and benefited from his association with prominent scientists at Yerkes such as Gerard Kuiper and William W. Morgan. Greenstein also became friends with Louis Henyey, another Yerkes scientist. The two men built a specially designed spectrograph for the observatory’s 40-inch refractor and coauthored several papers together. Finally, at McDonald Observatory, Greenstein was introduced to the research possibilities enabled by access to large optical telescopes.

After his fellowship ended, Yerkes Observatory invited Greenstein to remain as an instructor. As he later described it, 1939 “effectively ended my youth” when he turned thirty and World War II broke out. His research interests shifted too. For example, he used instruments at Yerkes and McDonald to obtain spectra of Upsilon Sagittari, a star with unusual elemental abundances. These studies encouraged Greenstein to devote more attention to the relative elemental composition of stars and their development over time, a project that he pursued more intently in the 1950s and 1960s.

Following the entry of the United States into World War II, Greenstein participated in war-related research brought to Yerkes by director Otto Struve. In mid-1942 he and Henyey formed a group to study new designs for optical systems. One of the more innovative devices Greenstein helped the Yerkes optical bureau produce was an all-sky camera that could photograph a large swath of the sky at one time.

After the war, Greenstein resumed his research at Yerkes. In addition to more traditional astronomical research, he continued to experiment with optical design and the possibilities of making observations with radio telescopes. Greenstein also used captured V-2 rockets as a tool to make astronomical observations from high in the atmosphere. In 1946, Greenstein designed a spectrograph that could make measurements in both the ultraviolet and visible light regions. With funding from the Johns Hopkins University’s Applied Physics Laboratory, his experiment was launched at White Sands, New Mexico, on the inauspicious date of 1 April 1947. Disappointment soon followed when Greenstein developed the film and found it unexposed. Consequently, Greenstein maintained a preference for ground-based observing throughout his career, preferring to avoid the complexity and risk of relying on space- or rocketborne instruments.

Greenstein Moves to Caltech . By 1948, Greenstein’s research had brought him substantial recognition in the astronomy community and he received numerous offers from institutions eager to lure him from Yerkes. He ultimately decided to accept an offer from Caltech president Lee A. DuBridge to lead that school’s astronomy program, and Greenstein arrived in Pasadena in June 1948, the same month the famous 200-inch telescope on Palomar Mountain was dedicated. Greenstein was a logical choice for Caltech as his background combined theoretical research and observing experience with big telescopes. The scientists Greenstein eventually recruited to Caltech’s astronomy program enjoyed access not only to Palomar (which Caltech operated jointly with the Carnegie Institution of Washington) but also telescopes on Mount Wilson and, in time, major radio astronomy facilities that Greenstein helped shepherd into existence.

Greenstein had a big task ahead of him as he built up and promoted Caltech’s astronomy program. While the Carnegie Observatory’s staff was large and included luminaries such as Edwin Hubble and Walter Baade, Caltech had only one other astronomer when Greenstein arrived—Fritz Zwicky, a brilliant and sometimes volatile Swiss scientist. Most of Caltech’s early teaching and administrative duties fell to Greenstein, and his program began with only a handful of graduate students who signed up for his yearlong courses on stellar evolution and star interiors.

Greenstein staffed Caltech’s astronomy program with scientists who could combine expertise in theoretical astrophysics with observations made on the world’s biggest telescopes. Greenstein also brought famous visitors such as Fred Hoyle and Jan Oort to Caltech to do research and teach his students. The strong linkage of physics with astronomy at the school meant that new areas of research and expertise were incorporated into Caltech’s program of traditional optical observing. As he described it in his memoir, he succeeded in converting physicists and engineers into “hyphenated-astronomers” who applied skills from other fields to astrophysical research. With the support of Caltech president DuBridge, Greenstein actively lobbied for his department’s participation in the newly emerging field of radio astronomy. His efforts bore fruit when Caltech’s Owens Valley Radio Observatory was dedicated in 1958.

Research Activities . Throughout his career, Greenstein frequently entered new areas of investigation, published several papers, and moved to another topic that caught his attention. His primary field of interest was the physics of astronomical objects, a topic that allowed him to combine his talents as a theoretician and observer. Greenstein’s ample share of telescope observing time helped him pursue diverse

research interests while skimming the scientific cream: “We had a big telescope, we could work on faint objects,” he said once in an interview. “You can't resist the fact that you’ve got an unbeatable gadget that nobody else has.”

Greenstein was an especially active user of the 200-inch telescope on Palomar for spectroscopic observations. One of Greenstein’s research goals was to use the telescope and its accompanying instruments as tools to probe the chemical composition of stars. During the 1950s, astronomers were keenly interested in understanding how nuclear reactions inside stars formed elements heavier than helium. Greenstein’s study of the relative abundance of certain elements and isotopes was enlightened by his association with physicists at Caltech’s Kellogg Laboratory (including William A. Fowler, who later won a Nobel Prize for his work on the formation of chemical elements in the universe) who were interested in the stellar creation of chemical elements. In 1956 he and Fowler coauthored a paper describing element-building reactions in stars.

Building on his long-standing interest in stellar compositions, in 1957 Greenstein began his Abundance Project, which he ran for the next thirteen years with support from the Air Force Office of Scientific Research. In addition to the project’s scientific results, the project served a pedagogical function by helping train a cohort of astronomy students, many of whom went on to have notable careers themselves. One of Greenstein’s notable papers from this period, written in 1959 with George Wallerstein and H. Lawrence Helfer, showed that the metal abundances in globular cluster giant stars were as much as a factor of a hundred below that of the Sun. Research such as this helped advance scientists’ knowledge of stellar abundances as a function of time and, more broadly, improved understanding of galactic chemical evolution.

Another long-term research program Greenstein undertook, after learning more about nuclear physics from Hoyle and Fowler, was the study of white dwarfs. Greenstein was drawn to this research for several reasons, not least because, as he put it, they were extraordinary celestial objects with “all the romance astronomy should have.” These objects form when nuclear burning at a star’s interior stops and its core begins to collapse and contract under its own gravity. Eventually the star becomes extremely dense with all the star’s material compressed such that the electrons cannot be packed any closer together. Besides being astronomically interesting, white dwarfs offered scientists an opportunity to measure the behavior of matter under extreme conditions that cannot be duplicated elsewhere. He was especially interested in studying their magnetic fields and luminosities. By the mid-1950s Greenstein had discovered over five hundred new white dwarfs and had contributed to astrophysicists’ better understanding of them.

In 1963 Greenstein and Maarten Schmidt (another Caltech astronomer) reported their observations of two quasi-stellar radio sources or quasars. While radio and optical astronomers had previously observed the two objects, innocuously named 3C 48 and 3C 273, Greenstein and Schmidt were the first to ascertain their cosmological significance. After reinterpreting the spectra Schmidt took at the prime focus of the 200-inch telescope, the two Caltech astronomers realized that the position of the spectral lines implied that 3C 48 was redshifted by 37 percent. This placed it more than five billion light-years from Earth, making it one of the most distant objects observed up to then. Their discovery made the cover of Time magazine in 1966 and helped reveal a universe that was far stranger and more violent than astronomers had suspected. Astronomers eventually identified thousands more quasars, work that helped open up a valuable new area of astronomical research with far-reaching implications for cosmology.

Greenstein’s Scientific Leadership . After Greenstein moved to Caltech, he became increasingly active as a leader of the science community and soon exerted influence over the priorities and funding for astronomical research. Greenstein began his service in this area as a member of the panel that helped oversee awards to astronomers from the Office of Naval Research, an important postwar patron for basic science. In 1952, after President Harry S. Truman signed the law creating the National Science Foundation (NSF), the new agency asked Greenstein to chair its advisory panel for astronomy. In 1954 he also served as secretary of a group that held a conference on organizing research in radio astronomy. This gathering helped create momentum that eventually resulted in the creation of the National Radio Astronomy Observatory in November 1956, which was funded by the NSF and managed by Associated Universities, Inc.

Greenstein contributed to defense-related research during the Cold War. For example, he consulted with the military on reconnaissance and optics-related topics including those for the U-2 spy plane. He was also a participant in Project Vista, a top secret “summer study” done at Caltech in 1951. The purpose of Project Vista was to determine how existing technologies as well as ones soon to be available (tactical nuclear weapons in particular) could repel a hypothetical Soviet invasion of Europe. Greenstein’s group explored how tools and expertise for astronomical research could be applied to aerial photography, infrared detection of troops and tanks, and the use of night-vision equipment.

In July 1969 the National Academy of Sciences (NAS) asked Greenstein to take responsibility for astronomy’s second “decadal survey.” These reports describe the field’s health, summarize important scientific advances of the past decade, and set research goals for the next ten years. More importantly, through a process of debate and negotiation closed to the public and the general astronomy community, the decadal survey committees present a prioritized list of instruments and facilities that should receive federal funding.

The survey Greenstein led differed from the earlier effort chaired by Albert E. Whitford in two important respects. First, it considered astronomy practiced from the ground, funded mainly by the NSF, along with space-based research supported by the National Aeronautics and Space Administration (NASA), which the Whitford report did not address. All techniques of observation would be examined. Second, Greenstein and his committee had a strong mandate from the NAS as well as the Office of Management and Budget to make recommendations for what should be funded first. “It was no longer possible to send a shopping list to the government.” Greenstein recalled, “They wanted priorities.”

Greenstein, as head of Caltech’s astronomy program, epitomized one style of astronomy—ground-based observing dominated by unparalleled access to large private telescopes in the West. By 1970 Greenstein was concerned about what he perceived as a disproportion between the federal support for astronomy at private institutions such as Caltech and that given to the national centers for optical and radio astronomy. Greenstein favored, as he phrased it in a 1963 letter to physicist Geoffrey R. Burbidge, “the benevolent dictatorship of the elite.” Nevertheless, the other members of Greenstein’s committee selected the Very Large Array as their number one funding priority. This was planned as a national facility for radio astronomy in Socorro, New Mexico, and estimated to cost at least sixty million dollars. While this recommendation was personally difficult for Greenstein to support, he wrote the committee’s final report and presented its recommendations to astronomy’s patrons throughout the 1970s.

Greenstein’s final major leadership role came in 1974 when the Association of Universities for Research in Astronomy, Inc. (AURA), a university consortium that managed the nation’s optical astronomy facilities, asked Greenstein to chair its board. Greenstein agreed although the task brought him additional conflict, especially with former Harvard classmate Leo Goldberg, over issues related to AURA’s mission and future growth.

Honors and Retirement . During his career Greenstein received many honors and awards. These included election to the National Academy of Sciences in 1957, the Bruce Medal of the Astronomical Society of the Pacific in 1971, the NASA Distinguished Service Medal in 1974, and the Gold Medal of the Royal Astronomical Society in 1975. He also served on the Board of Overseers for Harvard University from 1965 to 1971 and received the title of Lee A. DuBridge Professor of Astrophysics at Caltech in 1971. Greenstein stepped down as head of Caltech’s astronomy program in 1972 and retired from Caltech’s faculty in 1980. Greenstein’s wife Naomi died in 2002 after sixty-eight years of marriage. Jesse Greenstein died later the same year, leaving behind two sons, Peter and George, the latter also an astronomer.

BIBLIOGRAPHY

All of the unattributed quotes used here are drawn from Greenstein’s correspondence and papers, which are in the Caltech Institute Archives, as well as his 1984 memoir. Further information may be found in oral history interviews Greenstein did, including those in the collections of the Niels Bohr Library at the American Institute of Physics in College Park, Maryland, and the Caltech Archives in Pasadena.

WORKS BY GREENSTEIN

With William A. Fowler. “Element Building Reactions in Stars.” Proceedings of the National Academy of Sciences of the United States of America 42 (1956): 173–180.

With H. Lawrence Helfer and George Wallerstein. “Abundances in Some Population II K Giants.” Astrophysical Journal129, no. 5 (1959): 700–719.

With Maarten Schmidt. “The Quasi-Stellar Radio Sources 3C48 and 3C273.” Astrophysical Journal140, no. 1 (1964): 134.

Astronomy and Astrophysics for the 1970s. 2 vols. Washington, DC: National Academy of Sciences, 1972–1973. The report was written by the NRC Astronomy Survey Committee, which Greenstein chaired.

Interview with Spencer Weart, 7 April and 21 July 1977, oral history interview, Niels Bohr Library at the American Institute of Physics, College Park, MD. “An Astronomical Life.” Annual Reviews of Astronomy and Astrophysics 22 (1984): 1–35. Greenstein’s own autobiographical recollections.

OTHER SOURCES

DeVorkin, David. “The Maintenance of a Scientific Institution: Otto Struve, the Yerkes Observatory, and Its Optical Bureau during the Second World War.” Minerva18, no. 4 (1981): 595–623. Discusses optics research Greenstein did at Yerkes.

———. Science with a Vengeance: How the Military Created the US Space Sciences after World War II. New York: Springer Verlag, 1992. Details early efforts, including those of Greenstein, to make astronomical observations with rocketborne instruments.

Edmondson, Frank K. AURA and Its US National Observatories. Cambridge, U.K.: Cambridge University Press, 1997.

Kraft, Robert P. “Jesse Leonard Greenstein.” Biographical Memoirs, vol. 86. Washington, DC: National Academy of Sciences, 2005. A biography of Greenstein by a former colleague.

McCray, W. Patrick. “The Contentious Role of a National Observatory.” Physics Today56, no. 10 (2003): 55–61.

———. Giant Telescopes: Astronomical Ambition and the Promise of Technology. Cambridge, MA: Harvard University Press, 2004. Both works by McCray discuss Greenstein’s experiences at Caltech.

W. Patrick McCray