March 20, 1997
Vol. 16, No. 13

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    Yerkes Observatory: A century of stellar science

    In 1997, one of America's first big-science centers, the University of Chicago's Yerkes Observatory, in Williams Bay, Wis., celebrates its first century. Conceived by three men -- a University president, a young astronomer and a mass-transit tycoon -- Yerkes Observatory is a child born of ambition crossed with opportunity.

    Although the low-altitude observatory and great refracting telescope have long been surpassed by mountain-top observatories with ever-larger reflecting telescopes, Yerkes is one of the "grand dames" of modern astronomy. Its hallways ushered in the age of astronomical photography, witnessed great discoveries in stellar and galactic astronomy and nurtured the careers of many great astronomers who were students and teachers there.

    Today, Yerkes bustles with activity. The great telescope, the largest of its kind ever built, is still actively used for research. The observatory serves as the home base for an international observatory at the South Pole. Its machine shops host engineering professionals who build instruments for astronomy, physics and medicine. And techniques to take the "twinkle" out of starlight are being tested and refined, with the eventual goal of producing ground-based images that rival those taken by the Hubble Space Telescope. Ambitious beginnings

    Yerkes Observatory owes its beginnings to its wealthy patron, Charles Tyson Yerkes; a visionary University of Chicago president, William Rainey Harper; and an ambitious young astronomer, George Ellery Hale.

    Hale was born in Chicago in 1868 and grew up in Kenwood, steps from where the University would rise in 1892. By age 13 or 14, Hale was already interested in astronomy, and before he completed his undergraduate studies in physics at MIT, he had invented a new astronomical instrument, the spectroheliograph, which revolutionized the study of the sun. After he graduated in 1890, Hale returned to Kenwood, where his father helped him establish the Kenwood Physical Observatory, with a 12-inch telescope, in his backyard. Although he never received an advanced degree, Hale was already recognized as a world leader in the field of astronomy by the age of 23.

    Harper, the first president of the University, saw an opportunity to acquire an observatory for his new university, and offered Hale a faculty position in 1891. Hale, distrusting Harper's motives, refused. But after Harper had secured Albert Michelson to head the physics department, and demonstrated his ability to attract top-flight scholars to the new university, he again approached Hale, who finally agreed to join the faculty. Hale's father, knowing of his son's desire to build bigger and better instruments, bequeathed the Kenwood Observatory to the University on the condition that a new observatory be built for not less than $250,000 within two years of the time that Hale began his appointment. Hale was appointed Associate Professor of Astro-Physics and Director of the Observatory in July 1892.

    At a scientific conference in Rochester that summer, Hale overheard the story of a failed University of Southern California project to build the world's largest telescope. Two glass disks, which had been ordered to be ground into a lens for a 40-inch telescope -- surpassing Lick Observatory's 36-inch refractor -- were languishing in an optician's shop in Massachusetts. Never one to pass up an opportunity to build a bigger and better telescope, Hale rushed back to Chicago, calculating that the cost for a completed lens, mounting and observatory, would be approximately $300,000.

    Opportunity next presented itself in the form of Yerkes, a streetcar magnate whose reputation had been sullied by charges of fraud, embezzlement and bribery. Yerkes, who made his fortune in Chicago financing the elevated tracks, the underground cable system and the Peoples Gas Company, was seeking to repair his reputation by making charitable contributions. It wasn't long before Hale and Harper found their way to Yerkes' door.

    The two academics sold Yerkes on the point that Lick's name would not have been nearly so widely known were it not for the famous observatory established as a result of his generosity. Yerkes agreed to foot the bill for the finest and largest telescope in the world.

    Hale set out to build a complete observatory facility, which would include not only the telescope and the building to house it, but instruments and equipment necessary for a complete astronomical laboratory. Yerkes initially balked at the price tag, but because news of his generosity had already leaked to the press, he acquiesced.

    The building of the telescope may not have enhanced Yerkes' reputation, but through his generosity, the world's first university astrophysical observatory, and America's second big-science research facility, was born. The telescope mounting, designed by the same engineering firm that built Lick's 36-inch telescope, was ready in time to be displayed at the 1893 World's Columbian Exposition in Chicago.

    Meanwhile, a suitable site for the observatory was sought. Yerkes stipulated that it had to be within 100 miles of Chicago; 26 sites were offered to the University. Sites along Lake Michigan were discarded because of their high humidity, which would affect the viewing with the telescope, and the most suitable site, after other locations were rejected for being too close to the city or too close to train lines (which would produce vibrations), turned out to be a 53-acre tract on Geneva Lake in Williams Bay, Wis. Testing showed it to be a favorable location, and future development seemed unlikely to include factories (which would produce smoke) because the area was already a popular summer resort.

    Groundbreaking for the ornate observatory building, designed by Henry Ives Cobb, began in the spring of 1895, and the lens for the telescope was completed by that fall. After a year and a half of construction, the supporting column had been installed in the dome and the terra cotta work on the building was completed. Fine marble trim and maple floors completed the interior decorations. In November 1896, the first Yerkes student arrived.

    Throughout the following year, the interiors of the laboratories and auxiliary telescopes were constructed, and finally, by May 1897, the 40-inch lens was transported to Yerkes and installed. The telescope was put to its first test on May 21. Hale was delighted.

    Eight days later, near-tragedy struck. The giant, 90-foot elevated floor -- which moved up and down four stories to give observers access to the eyepiece of the telescope -- collapsed, just hours after astronomers had finished observing for the night. In order to prevent a similar accident, the cable connections that moved the floor up and down were redesigned. It was August before the floor was reinstalled, and October before the motors to move the dome and telescope were replaced.

    The observatory was finally dedicated on Oct. 21, 1897, with a gala celebration that included University Trustees as well visiting astronomers and physicists from around the world.

    Although Yerkes' great telescope would be surpassed within 10 years by Hale's burning desire to build bigger and better instruments -- he went on to build a succession of "world's largest" telescopes: the 60-inch at Mount Wilson, then the 100-inch and finally the 200-inch at Palomar -- the observatory is certainly one of the most famous in the world for the collection of people who passed through its portals (see sidebar). And the 40-inch refractor is the largest of its kind ever used -- a lens larger than 40 inches in diameter begins to distort under the pull of gravity, and larger telescopes must be built using mirrors to focus the light.

    The collection of astronomers at the dedication in 1897 formed the seed of what is now the American Astronomical Society, the society for professional astronomers in the U.S. Also in those early days, Hale founded the professional astronomers' journal, the Astrophysical Journal, whose editorial offices were based at Yerkes until the 1960s. The journal is still published by the University Press.

    Yerkes today

    Yerkes Observatory's location makes it a poor cousin to a high, dry mountaintop observing site. But as an intellectual center for astronomy, it has often had no equal. Astronomers based at Yerkes have traveled to other telescopes for their research, and Yerkes has managed several remote telescope facilities at different points in its history.

    In the late 1920s, a wealthy Texas banker, William J. McDonald, bequeathed nearly a million dollars to the University of Texas to build a large telescope. Lacking an astronomy faculty, Texas was at a loss for how to proceed in building an observatory. A marriage between Chicago, which had no money to build a large telescope in the southwest, and the University of Texas, which had money but no astronomers, was brokered under the leadership of then-director Otto Struve. Yerkes Observatory built and managed the McDonald Observatory -- and its 82-inch reflector -- for 30 years, until 1962, when the University of Texas astronomy department grew to the point that it could take over the management of the observatory.

    Today, Chicago is one of five academic partners that manage the Apache Point Observatory in New Mexico, and Yerkes serves as the headquarters for another remote observatory, the Center for Astrophysical Research in Antarctica at the South Pole.

    CARA's projects include an infrared telescope, which captured unforgettable images of Comet Shoemaker-Levy 9 crashing into Jupiter; a radio telescope used to study the origin of the universe; and a highly successful outreach program, called Space Explorers, that teaches math and science to inner-city high school students through astronomy. The Space Explorers spend 10 days every year at Yerkes, observing with the telescopes and conducting experiments on the grounds.

    A 41-inch reflecting telescope at Yerkes serves as the testbed for a high-tech optical device that takes the twinkle out of starlight. A Defense Department castoff, the Wavefront Control Experiment is helping astronomers design an affordable adaptive optics system. The deformable mirror, which corrects for turbulent atmospheric conditions, allows astronomers to take images from ground-based telescopes that rival those taken from space.

    The 40-inch refractor is also still actively used in research. Its nearly century-long history of photographic plates of stars allows astronomer Kyle Cudworth, Professor in Astronomy & Astrophysics, to compare photographic plates taken decades ago with ones taken today, to study the motions of stars relative to each other. These studies will help pin down the amount of dark matter in our galaxy, the non-luminous "glue" that gravitationally holds the Milky Way together.

    In the Yerkes engineering laboratories, engineers are building instruments for use on telescopes around the world as well as instruments for the University Hospitals and other institutions.

    The Astronomy & Astrophysics Department, which began to migrate to the Hyde Park campus in the 1960s after more than six decades at Yerkes, is again one of the leading astronomy departments in the world, with a diverse faculty of observers and theorists.

    As Yerkes Observatory prepares to enter its second century, the terra cotta figurines adorning the columned entrance stand guard over the marbled entryway, observing the continuing intellectual legacy passing through its door.

    -- Diana Steele The early history of Yerkes Observatory is chronicled in a new book by former Yerkes student Donald Osterbrock (Ph.B.'48, S.B.'48, S.M.'49, Ph.D.'52). Yerkes Observatory, 1892-1950: The Birth, Near Death and Resurrection of a Scientific Research Institution, is published by the University of Chicago Press.