Stewart L. Sharpless (1926–2013)

Stewart Sharpless died on Saturday the 19^th of January, 2013.

Stewart Lane Sharpless, a respected professor emeritus of astronomy at the University of Rochester, died in Rochester on January 19, 2013. He had carried out fundamental investigations pertaining to the structure of the Milky Way Galaxy and established the C. E. Kenneth Mees Observatory of the University of Rochester as a center for astronomical research, graduate and undergraduate astronomical education, and public outreach.

Sharpless was born in Milwaukee, Wisconsin, on March 29, 1926. His interest in astronomy was aroused when he was a young teenager by observing a close opposition of Mars through a small telescope. This interest continued through his high school years and led him to a lifelong career in astronomy.

Sharpless’ first paper, on which he appeared as a co-author with W. W. Morgan (1906–1994), was published while he was a 19-year-old student at Yerkes Observatory [1]. He continued on to do graduate work with Morgan at Yerkes, and he assisted Morgan and Harold L. Johnson (1921–1980) with calculations that helped define the important Johnson–Morgan UBV photometric system. Working under Morgan’s direction, Sharpless and fellow graduate student Donald Osterbrock (1924–2007) carried out several studies of H II regions that enabled them to obtain distance estimates for a significant number of O and B stars.

Sharpless completed his Ph.D. dissertation at Yerkes Observatory under Morgan’s direction. His thesis, entitled “A Study of the Orion Aggregate of Early-Type Stars,” was awarded by the University of Chicago in 1952 [2][3]. In the same year, he, Morgan, and Osterbrock employed their distance determinations for O and B stars to trace out two spiral arms of the Milky Way galaxy [4].

Following the completion of his dissertation, Sharpless was awarded a Carnegie Fellowship at the Mount Wilson and Palomar Observatories, where he worked with Walter Baade (1893–1960) and Rudolf Minkowski (1895–1976). He then accepted an appointment at the U.S. Naval Observatory (USNO) in Flagstaff, Arizona, where he studied H II regions in the Milky Way Galaxy. He is perhaps best known for the catalogue of 313 H II regions he published in 1959 while on the staff at the USNO ([5], succeeding an earlier catalogue of 142 such regions: [6]). With more than 840 citations, it is a resource that has been well-mined over the subsequent decades by astronomers working in many different wavelength regimes. Another highly cited paper from Sharpless’ USNO years, published in collaboration with several colleagues, concerned the photometry of stars in galactic cluster fields [7].

In 1964, after having advanced to the position of director of the USNO Astrometry and Astrophysics Division, Sharpless accepted an appointment as director of the newly established C. E. Kenneth Mees Observatory and as a member of the astronomy faculty at the University of Rochester. Located in the Bristol Hills, 40 miles south of Rochester, New York, the observatory is situated atop a high hill overlooking Canandaigua Lake at the site of a former Gannett family retreat. Sharpless threw himself into his new role energetically. He obtained an NSF grant (the first of several) to update the undergraduate astronomy courses. He helped to persuade the university to establish a Ph.D. program in astronomy—paralleling an existing Ph. D. program in physics and astronomy that focused on theoretical astrophysics—to capitalize on the new observatory. He further undertook supervision of the research of several graduate students in observational astronomy projects. He also continued to collaborate with former USNO colleague Otto G. Franz, obtaining spectra of spiral galaxies with the 84-inch (2.1-meter) telescope at Kitt Peak National Observatory (KPNO) to investigate the relationship between the spectral and morphological types of galaxies [8].

By the late 1960s and early 1970s, Sharpless had obtained additional NSF grants to expand the undergraduate astronomy laboratory courses and to purchase a 12-inch Tinsley telescope, which was installed in a 16-foot dome atop the newly constructed Space Science Building on the university campus. In addition, he had obtained on indefinite loan from the Carnegie Institution of Washington an image-converter tube, which was adapted for direct photography and installed on the 24-inch telescope at the Mees Observatory. In 1970–71, Harvey B. Richer and Anthony Wawrukiewicz received their respective doctorates for astronomical research completed under Sharpless’ supervision [9][10]. Each has gone on to productive careers. In the fall of 1972, Sharpless was on leave at the Lowell Observatory in Flagstaff, Arizona, where he used the 72-inch telescope to obtain spectra of B-type stars in the Orion belt region. Upon his return to Rochester, he and J. Graeme Duthie (1934-2019) assembled a two-channel photometer for the Mees Observatory telescope, which they used to study lunar occultations of stars.

Judith L. Pipher joined the astronomy faculty at the University of Rochester in 1971. She immediately set to work establishing observational infrared astronomy as an area of expertise within the Department of Physics and Astronomy, and she involved Sharpless and others of her more senior colleagues in this work. In 1976, she and Sharpless supervised a senior thesis that made use of image-tube observations, and they — together with Jim Houck (1940–2015) from Cornell University — used the Carnegie image tube at the Mees Observatory to search for planetary nebulae in globular clusters. That same year they and other colleagues and students published a multi-wavelength optical, infrared, and radio observation of the S 106 complex — a bipolar nebula that is being ejected from the young, massive star IRS4 — from Sharpless’ 1959 catalogue [11]. They continued to work together closely in subsequent years, next focusing on the compact H II regions S 88 B [12] and S 235 A/B [13][14]. In 1982, they jointly offered a course in astronomical techniques, developed the previous year with pilot funding from NSF, supervised two senior theses, offered a three-week summer internship program at the Mees Observatory, supervised graduate students in obtaining images of biconical nebulae and Sharpless H II regions and in constructing an optical polarimeter for the observatory. Sharpless secured the loan of an S-1 image tube from KPNO in 1983, and he and Pipher supervised its adaptation to and installation on the Mees Observatory’s 24-inch reflector. They also acquired two Apple II microcomputers for the undergraduate astronomy laboratories, and the following year Sharpless programmed them with interactive exercises for the undergraduate astronomy laboratory courses. Sharpless also supervised the optical part of Marc Lacasse’s Ph.D. thesis [15], with Pipher supervising the infrared part and H. Lawrence Helfer supervising the theory section. Lacasse continues to work on optical interferometry of variable stars.

In the final decades of his life, Stewart Sharpless devoted himself to working with children and youth with a wide range of emotional and behavioral challenges at the Hillside Children’s Center in Rochester. His astronomical legacy had long been firmly established. Very few scientists are granted the opportunity to have their names immortalized, but he is one of them. The Sharpless objects catalogued in his 1959 paper will ensure that he is remembered for centuries to come, just as is the case with Charles Messier. In addition, the effort Sharpless devoted to establishing the C. E. K. Mees Observatory as a regional center for astronomical research and education has provided a firm foundation for the careers of a number of men and women already, as it will continue to do for generations yet to come.