Changes at Yerkes Observatory, An Artifact of Wisconsin's Astronomical Glory Days

Mar 12, 2018

Stargazers can take note. Soon, you may not be able to use the historic Yerkes Observatory on Geneva Lake in Williams Bay, Wisconsin.

The observatory, built in the 1890s, has in recent decades been used primarily for education and outreach. The University of Chicago, which runs the observatory, announced that it will be ceasing its operations at the facility on October 1, 2018.

The major attraction at the observatory is the 40 inch in diameter telescope, once the largest in the world, and to this day the world's largest refracting telescope.

UWM physics Professor Jolien Creighton explains, “Yerkes is a refracting telescope, which means that it focuses light on a photographic plate or an eyepiece using lenses, like eyeglasses.”

But as of the mid-twentieth century, this type of telescope has been fairly obsolete. “More modern telescopes usually use mirrors to focus the light," he says. "[Also], modern telescopes tend to have much, much larger mirrors and collecting surfaces than Yerkes does.” 

The world's largest refracting telescope at Yerkes Observatory in Williams Bay, Wisconsin.
Credit Dawn Erb / UWM School of Astronomy, Gravitation & Cosmology

Another issue Yerkes has faced is light pollution. Street and building lights give cities a glow that makes it hard to see the stars above. "So if you go out at night and look up in Milwaukee, you can see a handful of stars, but you won’t see things like the Milky Way or Andromeda or other galaxies,” Creighton explains.

It’s one of the reasons Chicagoans put the observatory in Williams Bay in the first place. But, these days, optical telescopes are up on mountains in places like Chile and Hawaii.

Since the World War II era, astronomy has become about more than just optical telescopes.

"Beginning in the 1960s, a number of astronomical satellites were launched, so that you could get outside of the atmosphere. The main advantage was that you could do astronomy in x-rays and then gamma rays and then ultraviolet infrared, in all wavelengths outside of the visible spectrum," says UWM Professor John Friedman. 

But, before the era of satellites, radio astronomy and modern optical telescopes, Yerkes was especially good for determining distances of stars by something called Parallax. "That's looking at the apparent change in a nearby star’s position as earth goes around the sun. That lets you know the absolute brightness of stars, and also from their distance you can build on the distance ladders to find the distance to other galaxies," Friedman says.

Credit Dawn Erb

In fact, in the early 1950s, astronomer Don Osterbrock helped discover the spiral shape of  the Milky Way through observations at Yerkes.

UWM Professor David Kaplan has been taking his students to the observatory for years. “It’s nice to show the students at UW-Milwaukee that Wisconsin used to be the center of astronomy,” he says. “Architecturally it’s very impressive. The old technology isn’t what we’d use now, but when it was built it was still really cool, and it’s interesting to look at.”

Kaplan’s student Nik Prusinski says that he was inspired by the observatory and had hoped to do further work there, because it’s a special place in our tech-driven world. “Typically now we use Hubble telescope data and it’s all in space and we download it on the computers and we work with it that way," he says. "But actually being able to go to a telescope that from Milwaukee is only an hour away and actually look at these objects in person, live, is an extremely different experience than just getting a computer image of it.”

Professor Kaplan hopes that there's a way for the University of Chicago to find some agency to take it over in an educational capacity. "I think that would really be a lost opportunity to not do that," he says. "But I understand that it’s an expensive facility to maintain and to run.”

University of Chicago spokesman Jeremy Manier says that's exactly why the university made the announcement nearly seven months early. Its hope is that staff, surrounding communities and interested parties can talk about long-term plans for the property. “We hope that it will continue as a valuable resource to the community and visitors to the Lake Geneva area,” he says.

Credit Dawn Erb