One Hefty Telescope The main event at Yerkes is the 40-inch refracting telescope, which is still the largest of its kind used for scientific research. "This is the greatest thing about this place," says Rees, who finished his Ph.D. at Yerkes in 1993 and has been coming back every summer since. "After 22 years, I still feel awe every time I come in here." The tube alone is 63 feet long and weighs six tons. The whole contraption with all its moving parts weighs 19 tons. The cathedral-like dome that houses the great telescope is 90 feet in diameter, and echoes with every footstep. Despite the telescope's heft, astronomers have traditionally steered the huge machine by hand. Because the telescope pivots around the middle of the tube, the eyepiece end can wind up several feet off the ground. To get close enough to see, astronomers have to raise or lower the whole floor. Rumor has it that when Carl Sagan was a grad student here, he raised the floor so quickly that it smacked into the telescope. Looking up reveals more evidence of grad student humor: a stuffed Spiderman pinned to the rafters.

The controls on the operator's desk haven't been changed in decades.

Images: Lisa Grossman/Wired.com

Frozen in Time The reason Yerkes' 40-inch telescope is the biggest in the world is largely because after it was built, astronomers changed their strategy. Refracting telescopes collect light through two lenses, a large one at the skyward end and a smaller one for the eyepiece. The design is simple, but the bigger the lenses get, the harder they are to support. Shortly after Yerkes' telescope was built, the astronomy community started switching to reflecting telescopes, which use one curved mirror to collect light and focus it onto an eyepiece or a camera. Reflectors can be much bigger and heavier because the mirror is supportable from the bottom. The biggest reflecting telescope in the world is the Gran Telescopio Canarias in the Canary Islands at about 34 feet (10.4 meters) across, more than 10 times wider than Yerkes' refractor. These developments left the 40-incher in the dust. But there are a few special cases where a refractor is still useful. Rees and Cudworth are working on the one research project the 40-inch telescope is still essential for: mapping the motions of stars within star clusters over the course of decades. Astronomers at Yerkes have saved glass plates of observations with the 40-inch telescope since 1900. The oldest plate (below) captures the globular cluster M5 in a 300-minute observing run on May 28, 1900. By comparing images of the same star clusters taken with the same telescope, "we can tell which stars are members of the cluster, how the cluster moves as a whole, and how the stars move with respect to each other," Rees said. "If you're interested in how stars change over decades as opposed to months, you need old observations." Images: 1) Lisa Grossman/Wired.com. 2) Kristine Heiney/Wired.com

A House of Glass Yerkes has a whole room full of these plates, 30,000 of them in all. Harvard has the largest plate collection, with 500,000 plates. Sadly, some observatories throw out their old plates. Astronomer Wayne "Ozzy" Osborn of Central Michigan University is spearheading a movement to preserve old plates, several of which are stored at Yerkes. Some of these plates, from the McDonald Observatory in Texas, are oil-stained. Image: Lisa Grossman/Wired.com

Don't Judge a Spectrograph by its Cover Astronomers at Yerkes did more than take pictures of star clusters. The observatory was the site of the demonstration of the Milky Way's spiral structure, the detection of carbon dioxide in Mars' atmosphere and the discovery of widespread interstellar gas in the galactic plane. It was also home to three Nobel laureates, including Subrahmanyan Chandrasekhar, namesake of the upper limit on the mass of white dwarf stars. The spectrograph used to map the Milky Way's spiral structure is on display in the observatory's hallway. "It's a horribly ugly instrument for such important work," Rees said. Image: Lisa Grossman/Wired.com

Change of Plans Yerkes owes its existence in the first place to solar astronomer George Ellery Hale, who was freshly appointed to the University of Chicago faculty in 1892. Hale overheard optician Alvan G. Clark complaining that he had two perfectly ground disks of glass 42 inches in diameter sitting uselessly in his workshop. The University of Southern California had promised to buy the lenses for their new observatory on Mount Wilson near Pasadena, but the plan fell through and the university defaulted on its payments. Hale pounced, and within a year the University of Chicago was in possession of the world's largest refracting telescope and was building an observatory to house it. Hale convinced transit tycoon Charles Tyson Yerkes, a man with a marvelous mustache and shaky morals, to donate nearly half a million dollars to the observatory. "Yerkes was, even by late nineteenth-century capitalist standards, a crook," Rick Rees told Wired.com. Yerkes had earlier spent time in a Pennsylvania prison for misappropriation of funds. He supported the observatory to try to buy himself a place in Chicago society, but it didn't work. Eventually Yerkes went to England and helped finance the London Underground. Images: 1) Yerkes Observatory. 2) Catherine Manix/Wired.com

Written in Stone The history is written into the building itself. Carvings of Zodiac symbols and the chariot of the sun adorn the front steps. The flat face (bottom) carved into the front pillars is supposed to be William Rainey Harper, the first president of the University of Chicago. The face with the big nose is supposed to be Yerkes himself, or maybe Rockefeller. There used to be several carvings of bees stinging this man on the nose, but they were all removed around 1900. Images: Catherine Manix/Wired.com

Lighter Shelves Yerkes once had one of the premier astronomical libraries in the country. The Astrophysical Journal, still an important journal in astrophysics, was founded at Yerkes in 1895, and 100 years of back-issues were housed in the library. But in the mid-1980s, the University of Chicago moved all the books that weren't duplicates back to the main campus. Half the library stacks are empty now. The books that remain still have their "University of Chicago Library" bookplates, with sad stamps on the opposite page saying, "No longer property of the University of Chicago Library." Images: Lisa Grossman/Wired.com

Floating on Air Among the most active parts of the observatory are its basement machine shops. Engineer Marc Berthoud is helping to construct an infrared camera called HAWC, or High-resolution Airborne Wide-band Camera, for the flying observatory SOFIA. SOFIA (the Stratospheric Observatory for Infrared Astronomy) is a hacked Boeing 747 jetliner with a hole in the back for a telescope to peer out of. It took its first images in May 2010. With HAWC, which will fly in early 2012, SOFIA will be sensitive to wavelengths of light between 40 and 300 micrometers, well beyond what the human eye can see. It will be able to take sharp images of dust-filled bands of gas in the Milky Way, and interstellar clouds that are invisible to optical telescopes. In order to sense the heat from glowing clouds of dust and gas, HAWC has to give off almost no heat itself. "The instrument is basically a refrigerator," Berthoud said, which is why it's so big. The delicate sensors inside have to be kept at just 0.2 degrees above absolute zero. HAWC is being built at Yerkes "because the know-how and the facilities are here," Berthoud said. "There's a nice collection of people here who are really good at machining and design." Now that the 40-inch telescope isn't used so much for research, the instruments being built at Yerkes are part of what keeps the observatory afloat. "If it weren't for HAWC, there wouldn’t be that much external money coming to Yerkes," Berthoud said. Image: Lisa Grossman/Wired.com

Uncertain Future In the late 1990s, the Yerkes staff considered registering the building as an official historical site. But at that time the observatory was still an active research center, and gaining historic building status would make it difficult to continue the pace of research. Ironically, research slowed down so much over the next 15 years that in March 2005, the University of Chicago announced plans to sell the observatory and its land to a developer who wanted to build a resort on the shores of Lake Geneva. A public outcry followed, and the village of Williams Bay refused to allow the necessary rezoning. A focus group of University of Chicago astronomers wrote up a proposal to shift Yerkes' main purpose from a place of research to an education and outreach facility. "It's an interesting question, where will this place be in 10 years?" Berthoud said. In the pessimistic view, "the University of Chicago will just support the place enough to keep the lights running," says Berthoud, and the building will fall apart. But in the optimistic vision, there will be classes and workshops for students and teachers alike, and opportunities for non-scientists to get their hands on the telescopes. "I see a very good possibility of this being a regional if not national level science education center. I think that's entirely doable," Cudworth says. Image: Lisa Grossman/Wired.com

WILLIAMS BAY, Wisconsin— Albert Einstein once said that he'd rather visit the Yerkes Observatory than Niagara Falls. And visiting this historic place, you can understand why. Back in its heyday, this 113-year-old palace of space science housed one of the best astronomical libraries in the country, the world's largest refracting telescope, and all the astronomy faculty and grad students from the University of Chicago. But these days, most astronomers would rather be in Chicago. In recent years, the university has reclaimed most of the books, the telescope's research time has been replaced with school tours, and the scientists have trickled 100 miles south to the main campus. Only a handful of researchers remain, and many don't stay year-round. "When I first came here, new faculty had a choice of where to go, Chicago or up here," said observatory director Kyle Cudworth, who has worked at Yerkes since 1974. "But by 10 years later, they were not given a choice. They were strongly encouraged to go to campus." Despite the exodus, Yerkes is still an active center of research and engineering. Cudworth and his former student Rick Rees (now a professor at Westfield State University in Massachusetts) use a century's worth of observations from the big telescope to track motions of stars in clusters, work that can be done only at Yerkes. And engineers working in the observatory's ancient cellars are constructing new instruments to fly on airborne telescopes. Wired.com recently took a tour of this majestic, history-rich observatory to learn why it claims the title "the birthplace of modern astronomy," and what will happen to it now. Image: Lisa Grossman/Wired.com