Astronomical Observatory (University of Illinois Urbana-Champaign)

Astronomy classes at the University of Illinois date to its earliest days. The first courses focused on measurement of the night sky and was taken by civil engineering students to sharpen their surveying skills. A small observatory consisting of a 4-inch refractor and a small transit telescope was constructed by 1872. The astronomy courses were typically taught by the mathematics department and by the early 1890s, several mathematics instructors wanted to do more with astronomy. An expanded astronomy curriculum would require a new larger facility.

The Illinois state legislature voted in 1895 to fund a new teaching observatory at the University of Illinois, providing $15,000 for construction. The site chosen was a grass knoll between Matthews Avenue and Burrill Avenue, just north of the Morrow Plots, a National Historic Landmark that is the nation's oldest experimental field. Contracts were extended to Charles A. Gunn, the architect and an instructor on campus, and Bevis and Company in Urbana as the general contractor with construction beginning in April 1896.[6] The building was completed by August at a total cost of $6,800.[5] The principle telescope was installed in November and the final telescope was in place by February 1897.

The first director of the observatory was George W. Myers. Myers was a Champaign county native who graduated from the university in 1888. He remained as a mathematics instructor also teaching the spring Descriptive Astronomy course. In preparation for the directorship he spent two years in Munich earning his Ph.D in astronomy. In his first year as director, G.W. Myers announced the discovery of the source of the variability in the star Beta Lyrae at the opening conference for Yerkes Observatory.[5] He served as director from 1897 until 1900 when he left for the University of Chicago.[5] W.C. Brenke, an astronomy instructor, served as acting director until a new director was hired in 1903.

Before 1907, all magnitude measurements for stars were obtained through visual comparison of relative brightness, a process that was slow and inexact. Later photographic methods would use starlight to make a representation on a photographic plate. Regardless, neither method was adequate for quantitative measurements. The drawback of previous methods of measuring stellar magnitude made the use of electricity for empirically gathering astronomical data revolutionary for the science of astronomy. Joel Stebbins' pioneering research for astronomical photometry took place at the observatory.[6]

The selenium cell photometer mounted on the refractor telescope in 1910

Stebbins arrived as director of the University of Illinois Observatory after he completed his Ph.D. at the University of California, Berkeley in 1903. Once Stebbins arrived fresh from his dissertation completed at Lick Observatory, he began a two-year study of the brightness of 107 binary stars using a Pickering visual photometer. The research, with the assistance of his wife, May Stebbins, investigated the relative brightness on binary stars using visual techniques. In a 1957 speech at the American Astronomical Society, Stebbins recalled the events which led to the electric cells:[6]

She [May Stebbins] wrote down the numbers as the observer called them, but after some nights of recording a hundred readings just to get one magnitude, she said it was pretty slow business. I responded that someday we would do all this by electricity. That was a fatal remark. Thereafter she would often prod me with the question, "When are you going to change to electricity?" It happened that within two or three months, the Department of Physics gave an open house, and one of the exhibits was in [the] charge of a young instructor, F.C. Brown. He showed how, when he turned on a lamp to illuminate a selenium cell, a bell would ring, when the lamp was off, the bell would stop. Here was the idea: Why not turn on a star to a cell on a telescope and measure a current?[6]

Stebbins and Fay C. Brown soon became friends and in time, they had a selenium cell positioned on the 12-inch (300 mm) telescope at the observatory. In the summer of 1907, after several attempts, the two achieved a light curve for Earth's moon and measured the moon's brightness during a lunar eclipse. This marked the first time in America that electricity was used to measure astronomical brightness.[5] Later Stebbins went further, discovering that by cooling the cell to zero degrees Fahrenheit he would double the cell sensitivity and diminish irregularities in the circuit tenfold, still further, by reducing the size of the cell the irregularities were reduced more. The pair went on to detect stellar intensity and activity that were previously unrecorded.[6] In 1909 their observations of Algol detected for the first time the second minimum as well as limb brightening. The coming of Comet Halley in 1910 allowed Stebbins, in May, to use his selenium photometer to study the comet.[5] Two years later Stebbins used the photometer and discovered four stars to be eclipsing binary stars: Beta Aurigae, Spica, Alpha Coronae Borealis and Delta Orionis.[5]

Although the selenium cell photometer was proving successful, it was difficult to use and not very sensitive. Illinois physics professor Jakob Kunz suggested that Stebbins try a photoelectric cell. Kunz had been experimenting on an improved photoelectric cell which was alkali based. Kunz's cell was the predecessor of the modern day "electric eye."[6] Stebbins left for a sabbatical in Europe in fall of 1912. While he was gone, Kunz and another Illinois physicist, W.F. Schulz, successfully tested a photoelectric cell photometer at the observatory.

Upon his return from sabbatical in August 1913, Stebbins ended his pioneering work with the selenium cell and began working with Kunz on the new photometer.

In 1915, Stebbins' object of study became the star involved in Myers' first big discovery at the observatory, Beta Lyrae.[5] He thus began an aggressive research program that produced a series of papers in the Astrophysical Journal on eclipsing binaries Lambda Tauri, Algol, 1H Cassiopeiae (HR 8926), ellipsoidal variables π5 Orionis, and b Persei, and Nova Aquilae (V603 Aquilae) in 1918. Stebbins and Kunz also travelled to Wyoming to study the Solar eclipse of June 8, 1918.[5] Dr. Elmer Dershem joined the observatory staff in 1917 and rebuilt the photometer in the summer of 1919. By 1922, Charles Wylie completed the first Illinois astronomy doctorate for his photoelectric studies of the Cepheid Η Aquilae, and Sigma Aquilae noting its variations due to tidal distortions.

In 1913, Stebbins was awarded the Rumford Prize of the American Academy of Arts and Science, and in 1915 the Henry Draper Medal of the National Academy of Sciences. The research was also supported by grants from the Draper fund of the National Academy of Sciences and the Rumford Fund of the American Academy of Arts and Sciences. Stebbins served as an officer of the American Astronomical Society and was one of the American delegates in 1918 to attend the organizational meeting of the International Astronomical Union in Brussels.

Stebbins left the University of Illinois in 1922 for the Washburn Observatory in Wisconsin and Dr. Robert H. Baker took over as the new Director of the University of Illinois Observatory. However, discovery and science did continued at the university's observatory.[5]

Stebbins' photoelectric photometer mounted on the 12-inch (300 mm) refractor in 1913.

When Robert Baker arrived he continued a photoelectric photometry program focusing on variable stars. He continued to use the 12-inch refractor until 1927 when a new photometer was constructed and attached to the 30-inch reflector telescope in the observatory annex.[7] He supervised two graduate students who worked on this equipment in the early 1930s. On May 27, 1933, the star Arcturus provided light which fell onto a photo cell in the observatory's annex and sent a signal to open the Chicago World's Fair.[5][7]

The Great Depression was soon in full swing[5] and the department budget fell from $1000 to $200. It was during this time that Dr. Baker authored a number of books. In 1930, he authored the textbook Astronomy, followed in 1932 by The Universe Unfolding, and his revision of Simon Newcomb's Astronomy for Everyone. In 1934 Baker described an imaginary trip to the moon in When the Stars Come Out. His second textbook, An Introduction to Astronomy also appeared in 1934. Introducing the Constellation was published in 1937 and, with the help of Howard Zim in 1951, Stars: A Guide to the Heavens. His textbooks were used across the country for undergraduate astronomy courses and praised as classics.

After two sabbaticals to Harvard, Baker's interest moved from photometry to the Milky Way. In 1939 the 30-inch reflector was replaced with a Ross photographic telescope and in the years 1939 through 1951, Baker used the observatory's photographic telescope to help count the stars in the Milky Way and determine their distribution as part of Harvard University's Star Counting Circuit.[7] This would be the primary research until Baker's retirement in 1951. The 12-inch refractor was only used for instruction, public open houses and for visiting school groups.

The university increased the size of the department and hired Dr. George C. McVittie as the next director. After his arrival in the fall of 1952, McVittie began the refurbishment of the Observatory's major instruments. The 12-inch refractor and the 3-inch transit telescope were restored in 1954 by the J.W. Fecker Company. He also began expanding the faculty. Dr. Stanley Wyatt joined the faculty in 1953, George Swenson and Ivan King in 1956, Kennth Yoss, John Dickel and James Kaler in 1964 and Edward Olson in 1966. With George Swenson's arrival, Illinois began a program of radio astronomy resulting in the Vermillion River Radio Observatory that opened in 1962. Prairie Observatory was an optical observatory consisting of a 40-inch telescope and was completed in 1967. By the time of Dr. McVittie's retirement in 1971, the one-astronomer department had expanded to nine faculty with research interests in relativity, cosmology, celestial mechanics, perturbation theory, dynamics of star clusters, planetary nebulae, planets, supernovae and radio astronomy. The department which produced only five advanced degrees prior to 1951 graduated 29 Masters and 14 Doctoral students during the McVittie administration.

On October 4, 1957, the very evening of the launch of Sputnik, students and faculty met at the observatory and constructed an improvised radio interferometer. They published the first precise ephemeris in the journal Nature in November. Their success helped gather momentum and funding for the radio astronomy program.

The observatory underwent major renovations and additions in 1956 and 1966 to accommodate the growing faculty (see architecture section below). In 1967, the 12 inch telescope at the observatory made its last professional photometric observations.[5] The University of Illinois' Astronomy Department moved out of the building in 1979. In 1986, thousands gathered at the site to observe Comet Halley's journey into the inner Solar System.[5]

The observatory is no longer used for research purposes, though the telescope is still used as a teaching tool in the university's astronomy classes.[4] In addition, the University of Illinois Astronomical Society uses the telescope often for amateur astronomy and astrophotography. The observatory dome underwent a renovation that included repainting in 1996.[4]

In 2009, Professors Leslie Looney and Benjamin McCall constructed a spectrometer on the ground floor of the observatory, and ran an optical fiber cable to the telescope in the dome. They used this to teach an astrochemistry class until the 50-fiber bundle was broken.

In 2013, the telescope was detached from its mount, lifted out of the dome through the dome slit, and placed on a truck to be shipped to Swarthmore, Pennsylvania to be refurbished by Ray Museum Studios. The telescope's optics were cleaned, as well as the exterior refinished. While the telescope was away, the dome was repainted, as were the interior walls and flooring. The total cost of the renovation was approximately $54,000.