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

Yerkes Observatory
DAWN ERB / UWM DEPT OF ASTRONOMY, GRAVITATION & COSMOLOGY

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.”

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.

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.

Source: UWUWM

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Seeing Titan with Infrared Eyes

Figure A

These six infrared images of Saturn’s moon Titan represent some of the clearest, most seamless-looking global views of the icy moon’s surface produced so far. The views were created using 13 years of data acquired by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on board NASA’s Cassini spacecraft. The images are the result of a focused effort to smoothly combine data from the multitude of different observations VIMS made under a wide variety of lighting and viewing conditions over the course of Cassini’s mission.

Previous VIMS maps of Titan (for example, PIA02145) display great variation in imaging resolution and lighting conditions, resulting in obvious seams between different areas of the surface. With the seams now gone, this new collection of images is by far the best representation of how the globe of Titan might appear to the casual observer if it weren’t for the moon’s hazy atmosphere, and it likely will not be superseded for some time to come.

Observing the surface of Titan in the visible region of the spectrum is difficult, due to the globe-enshrouding haze around the moon. This is primarily because small particles called aerosols in Titan’s upper atmosphere strongly scatter visible light. But Titan’s surface can be more readily imaged in a few infrared “windows” — infrared wavelengths where scattering and absorption of light is much weaker. This is where the VIMS instrument excelled, parting the haze to obtain clear images of Titan’s surface. (For comparison, Figure B shows Titan as it appears in visible light, as does PIA11603.)

Figure B

Making mosaics of VIMS images of Titan has always been a challenge because the data were obtained over many different flybys with different observing geometries and atmospheric conditions. One result is that very prominent seams appear in the mosaics that are quite difficult for imaging scientists to remove. But, through laborious and detailed analyses of the data, along with time consuming hand processing of the mosaics, the seams have been mostly removed. This is an update to the work previously discussed in PIA20022.

Any full color image is comprised of three color channels: red, green and blue. Each of the three color channels combined to create these views was produced using a ratio between the brightness of Titan’s surface at two different wavelengths (1.59/1.27 microns [red], 2.03/1.27 microns [green] and 1.27/1.08 microns [blue]). This technique (called a “band-ratio” technique) reduces the prominence of seams, as well as emphasizing subtle spectral variations in the materials on Titan’s surface. For example, the moon’s equatorial dune fields appear a consistent brown color here. There are also bluish and purplish areas that may have different compositions from the other bright areas, and may be enriched in water ice.

For a map of Titan with latitudes, longitudes and labeled surface features, see PIA20713.

It is quite clear from this unique set of images that Titan has a complex surface, sporting myriad geologic features and compositional units. The VIMS instrument has paved the way for future infrared instruments that could image Titan at much higher resolution, revealing features that were not detectable by any of Cassini’s instruments.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’S Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The VIMS team is based at the University of Arizona in Tucson.

For more information about the Cassini-Huygens mission http://saturn.jpl.nasa.gov/home/index.cfm. The visual and infrared mapping spectrometer team homepage is at http://www.vims.lpl.arizona.edu.

Source: NASA

First Man (2018)

Director: Damien Chazelle
Writers: Josh Singer (screenplay by), James R. Hansen (based on the book by)
Stars: Ryan Gosling, Claire Foy, Jason Clarke
Production Companies: DreamWorks Universal Pictures
Release Date: October 12, 2018
First Man (2018)

July 20, 1969 Armstrong Walks on Moon

At 10:56 p.m. EDT, American astronaut Neil Armstrong, 240,000 miles from Earth, speaks these words to more than a billion people listening at home: “That’s one small step for man, one giant leap for mankind.” Stepping off the lunar landing module Eagle, Armstrong became the first human to walk on the surface of the moon.

Source: History.com

Source: Chasing the Moon | Coming to American Experience Summer 2019