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Yerkes Observatory in the 21st Century

There are a number of observatories around the world that fall into the category of “venerable and still usable”. Think of Mount Wilson and its 100-inch Hooker telescope. Or consider Palomar’s collection of scopes, including the 200-inch Hale. It also showcases the historic Samuel Oschin Telescope, a survey instrument that has produced mind-boggling images of the universe. Then, there are the facilities at Pic du Midi, in England, the observatories in Australia, and South Africa. These (and many others) are places where astronomy’s scientific advances into astrophysics began. And, of course, there’s Yerkes Observatory, one of the most venerated in the U.S. For multiple generations of astronomers, it was among the best places to do their science. They spread out to other observatories to teach their own students and continue the exploration of the universe.

Yerkes Observatory as photographed by Wikipedia user Mumford. The facility is in Williams Bay, Wisconsin, and has been run by the University of Chicago for many years. A new agreement may see it transferred to a private foundation to continue its astronomy and education mission.

I learned of the Yerkes history when I first visited it in the 1990s. It was a marvelous place to be, a sort of “shrine” to early astrophysics. A year or so back, while doing research for my latest book, I had a chance to dig further into its history, and its future looked very uncertain. That may change soon, for reasons I’ll get to below.

A Nineteenth-century Observatory

Astronomer George Ellery Hale founded Yerkes in 1897. He also played a significant role in the founding and building of other observatories in California, as well. The late nineteenth century was just about the time astronomy began to embrace the astrophysical side of things. Through the succeeding hundred years, astronomers from around the world used Yerkes as a training ground and research center. This included my own grad school advisor John C. Brandt, such folks as Carl Sagan, E.E. Barnard, Gerard Kuiper, and many others. It has also been a noted center for astronomy educators to learn their trade.

Yerkes is the birthplace of modern astrophysics. Work done there forms a basic underpinning to much of astrophysics. That includes the development of a spectral classification method called the MKK system (named after astronomers William Wilson Morgan, Philip C. Keenan, and Edith Kellman. Yerkes also served as an inspiration for other observatories, particularly Mount Wilson in California. An 1897 meeting at Yerkes to herald its opening is often been cited as a pivotal point in the formation of the American Astronomical Society. (I’ve been a member since 1992).

The centerpiece of the Yerkes Observatory has always been the 40-inch (102-cm) Alvan Clark & Sons lens housed in a Warner & Swasey-built mount. It was the largest refracting telescope in the world. Today, it remains a wonderful example of instrument-making art and craft. Over the years, the observatory acquired other instruments, including telescopes, spectrometers, micrometers, spectroheliograph, and specialized cameras and imagers.

A Change of Direction for Yerkes Observatory

There’s no question that Yerkes has an honored place in astronomy history. Yet, for all its storied background, the University of Chicago (its parent institution) didn’t want to keep running Yerkes anymore. The administration cited the very real costs of upkeep for the aging facilities as one reason. Also, encroaching light pollution has a serious effect on the institution’s ability to do advanced astrophysical observations. In 2005, the university announced it was going to sell the entire facility and grounds to a developer. The plan was to build luxury homes and other facilities. In short order, Yerkes would no longer be an observatory. This, despite its continued use as an educational facility.

The decision to turn Yerkes and its grounds into an exclusive homesite was not popular. In fact, the developer faced intense criticism, particularly among local residents. The astronomy education community was not happy about losing access to Yerkes. The outcry was effective and the development plans got dropped. That didn’t stop the university from looking for a way to unload the place. About a year ago (March 2018), they announced an October 1st closure of Yerkes to the public and continued to look for a way to dispose of the property.

The Yerkes Future Foundation Steps In

Not long after the closure decision was announced, a group of local residents called the Yerkes Future Foundation stepped up to the plate. They proposed to take over the facility and continue its mission and began discussions with the university. On November 6, 2019, the two sides announced an agreement in principle to transfer the property to the foundation. There are, as yet, no public details about the agreement itself.

There is some information available about future plans, however. The foundation will restore the buildings and telescopes and reopen the facility to the public. Educational programs for students, as well as access for astrophysicists, will be set up. These should preserve the Yerkes role in teaching the next generation of astronomers while promoting continuing research programs.

That’s where the future of Yerkes stands at the moment. I really do hope that this venerable place and its priceless Alvan Clark telescope will continue to be used. The mechanics are still good, and even though light pollution is brightening the nearby skies, there’s still science and learning to be done! Stay tuned as this saga continues forward.

Note: the book I referenced above is The Discovery of the Universe: A History of Astronomy and Observatories. It is due out next week in hardback in the UK and in electronic form in North America.

There’s a planet out there, orbiting a star. There are, in fact, many of them out there. Thanks to studies made from ground-based observatories as well as such orbiting telescopes as HST, Kepler, TESS, and others, we know about thousands of them. We know they’re there. We know that some are hot Jupiters. Others are more Earth-type worlds. Some are gigantic ice giants like Neptune or Uranus. There are direct images of such worlds, but they’ really don’t show us surface characteristics. Those types of images may come someday. For now, we’re limited to detecting worlds and characterizing them based on spectral studies or direct imaging. That’s how we get knowledge about their orbital positions and information about their stars.

Why study these worlds? There’s a lot we are still learning about our own solar system. Its history and evolution are still a story to be filled in with data. Looking at other planetary systems gives us a look at our own in different stages of development. It’s a bit like looking at a forest and seeing trees in different stages of growth. There are stars and planetary systems in our neck of the galactic woods. So, there’s very likely a good example of planetary collections at all stages of life

The Lens of Gravity

Finding worlds around distant stars is hard. They’re small and dim, compared to their stars, which are large and bright. Astronomers use all kinds of techniques to spot them. To me, one of the more interesting ways is via gravitational lensing, which sounds weird but is perfectly natural. It needs an object with a strong gravitational pull to pass in front of a more distant object. Gravity warps space. Anything that moves through warped space is affected. So, a beam of light from a more distant object that passes through the warped gravitational space around a foreground object looks warped. In more practical terms. the image of the more distant object looks warped. That’s because the light’s path is warped like a funhouse mirror by the gravity of the closer object.

Lensing History

I first learned about gravitational lensing as it relates to looking at very distant objects, such as quasars. Their light passes through warped space, and the effect can be downright eerie. The Einstein Cross, for example, is the light from a single quasar. That light gets warped as it passes through the gravitational pull of a galaxy cluster closer to us than the quasar. The result: a “cross” made of four images of the single quasar. Those images are created by the lensing effect of the galaxy cluster.

So, if that works for more distant, bright objects, can it work for closer, smaller, dimmer objects? It turns out it can. And, astronomers have known this for quite a while.

A Small Planet Caught in a Lens

Viewing a star with a Neptune-sized planet using the gravitational lensing technique via an artist’s concept. The inset shows the star and planet in detail. Courtesy: University of Tokyo.

For example, a couple of years ago, an amateur astronomer spotted a gravitational lensing event that involved one star passing in front of another star. Now star-star lensing events are understandable but still rare. While there are a lot of stars in a galaxy, the chances of one passing in front of another from our point of view are still low. Space is big and not as “packed” as we’d like to think in most places. So, finding one of these is kind of an astronomical jackpot. Data from the event can give information about both stars.

Anyway, the observer, named Tadashi Kojima (from Japan), spotted this event and immediately sent out an alert. Pretty soon everybody was checking it out. That included astronomers at the big observatories. It turns out that the lensing event also showed that the foreground star has a planet in orbit. Astronomers from the University of Tokyo observed the event using telescopes around the world for more than three months. The data they collected about the star and its planet was fascinating. For one thing, the star is about half the mass of our Sun. Its planet is more massive than Neptune, but orbits at the same distance as Earth does from the Sun. It’s also a relatively close neighbor, lying about 1,600 light-years away. The more distant star was about a thousand light-years more distant.

What Does it Mean?

We are so accustomed to OUR Uranus and Neptune-type planets out in the distant reaches of the solar system. Sometimes that leads people to think that ALL solar systems have their giant planets out in the boonies. But, as planetary scientists study more of these exoplanet systems, they find giant planets in remarkably close orbits. That leads to questions about where ours formed in the early protoplanetary nebula. If they formed close in, then why are they now out in the solar system sticks? Studying more stars with giant planets close in can help answer those questions for our own solar system. This particular discovery also tells astronomers that more Neptune-sized planets orbit close to their stars at some point in their evolution.

So, gravitational lensing, which has been an observational tool for years now, is rooting itself firmly into the toolbox of planetary detection methods. It’s a perfectly useful way to peer at distant objects and get major data about them. Ultimately, it all comes back to help us understand how and why the universe works in ways both big and small.

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