SkyWord

Skyword: March 2016

MARCH 2016

Director’s Message

Director's Message

Taft Armandroff

Taft Armandroff, Director

Frank and Susan Bash Endowed Chair

Welcome to SkyWord. It’s a pleasure to share the news of McDonald Observatory’s recent research, outreach, and an inside look at some members of our team.

The Hobby-Eberly Telescope (HET) has been transformed. Its new wider field of view and capable new instruments will enable in-depth studies of dark energy, extra-solar planets, and more. The first article in this issue gives an overview of the telescope upgrade. Extensive testing of the upgraded HET’s optical system shows that it forms sharp images over its full field of view, meeting the demanding performance requirements we set early on. The HET team is currently working to complete re-commissioning of the telescope.

The second article highlights research by W.J. McDonald Postdoctoral Fellow Natalie Gosnell, who used Hubble Space Telescope (HST) to better understand “blue stragglers,” stars that look much younger than their age. Gosnell’s observations with HST’s Advanced Camera for Surveys led her to formulate a theory that might explain how two-thirds of blue stragglers formed. Her work is published in the December 2015 issue of The Astrophysical Journal.

In outreach news, the Frank N. Bash Visitors Center Manager Frank Cianciolo provides a history of McDonald Observatory solar viewing. Frank highlights recent upgrades, the award-winning work of Kevin Mace, and donations from the Semmes Foundation, Lloyd Overcash, and Wayne Rosing that funded the upgrades. Links to additional images and time-lapsed video from McDonald Observatory’s solar viewing system are available at the end of Frank’s article.

The Spotlight section features Bill Wren, who recently received the Hoag/Robinson Award from the International Dark-Sky Association (IDA). Bill’s passionate and effective advocacy for astronomy-friendly lighting has resulted in many laws and zoning rules, as well as a recent notice from the Texas Railroad Commission reminding oil and gas rig operators of existing law and best practices in outdoor lighting.

Finally, our Featured Photo shows Wayne and Barbara Alexander ringing the rocks at the groundbreaking ceremony for the Giant Magellan Telescope (GMT) in Chile. The University of Texas at Austin is partnering with 10 other institutions to build this world’s largest telescope, which is expected to begin science in 2022. One notable and tangible contribution from The University of Texas at Austin to GMT is the design of the GMTNIRS infrared spectrograph. Developed by Dan Jaffe and his team, the instrument is based on the highly successful IGRINS instrument Jaffe built for the Harlan J. Smith Telescope at McDonald. GMTNIRS is funded by the GMT partnership.

Research

Upgraded Hobby-Eberly Telescope Sees First Light

by Rebecca Johnson

FORT DAVIS, Texas — After several years and a massive team effort, one of the world’s largest telescopes has opened its giant eye again. The Hobby-Eberly Telescope (HET) at The University of Texas at Austin’s McDonald Observatory has completed a $25 million upgrade and, now using more of its primary mirror, has achieved “first light” as the world’s third-largest optical telescope.

“This upgrade makes HET the most powerful wide-field spectroscopic telescope worldwide, and we expect unique scientific discoveries from it,” observatory director Taft Armandroff said.

The new HET made its first image on July 29. After extensive testing and fine-tuning, the team reports that image quality meets specifications — sharp enough to resolve features one mile across on the surface of the Moon (or in astronomical terms, a resolution of 0.9 arcseconds.)

Spurred by the HET collaboration’s desire to do big science projects, including the forthcoming Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), the upgrade was a major undertaking that includes new optics, new mechanics, and new software. Today, HET is essentially a new telescope — only its primary mirror remains unchanged.

What makes the new HET great? One major factor is the new Harold C. Simmons Dark Energy Optical System. This set of optics sits above the telescope’s main mirror, in the location usually occupied by a secondary mirror.

McDonald Observatory chief scientist Phillip MacQueen designed the system. He explained that the Simmons System, informally called a “corrector,” is a complex set of optics, including four mirrors, that achieves two key tasks.

First, it brings light from the primary mirror into sharp focus. Because HET’s primary mirror is spherical rather than parabolic, it does not focus light into a sharp image. To make sharp images, the primary mirror needs to feed light into a corrector before it is fed into scientific instruments.

Second, the Simmons System allows good images from all parts of the telescope’s greatly enlarged field of view. The telescope’s field of view has increased by 120 times, and is 70% of the diameter of the full Moon (that is, 22 arcminutes or one-third of a degree).

Research Associate Hanshin Lee managed a nearly seven-year process by The University of Arizona College of Optical Sciences to build and test the $6 million Simmons Optical System. It was a tough process to verify the optics and ensure they were set up properly.

The work consisted of shaping the four mirrors (three 1-meter mirrors and one 0.25-meter mirror) to exacting specifications and testing those shapes, applying a specialized reflective coating, putting them together into a single package, and aligning them to high accuracy.

Once the Simmons System was built, transporting the 2-ton assembly safely from Tucson to McDonald Observatory in West Texas was an undertaking fraught with danger. Its optics were so finely balanced that hitting any pothole could spell a problem. It made the 500-mile trip overnight, going 45 miles per hour, with a police escort and arrived May 28. Later testing verified that nothing had moved in the process — the optics were still aligned within a fraction of the width of a human hair.

Lee said that throughout the difficult building and testing process “our staff was really fantastic in stepping up — while solving problems, they showed a lot of creativity and conviction that they could do it,” noting that it took  many people with different talents to make the project a success.

The Simmons System is “one of the most complex optical systems ever deployed in astronomy,” said Gary Hill, McDonald Observatory’s chief astronomer and principal investigator for HETDEX.

Because it allows more of HET’s 10-meter by 11-meter mirror to be used, it makes HET a larger telescope. The mirror’s effective size has increased from 9.2 meters to 10 meters. This means that HET is now tied for the world’s third-largest optical telescope.

The telescope also features a new tracker that supports the Simmons System (and a suite of instruments to ensure its alignment to extremely high precision) as it moves across the primary mirror tracking cosmic targets across the sky. The new tracker was built by The University of Texas at Austin Center for Electromechanics. A McDonald Observatory team led by Niv Drory developed HET’s entirely new control system.

The upgraded telescope is now able to track and guide on cosmic targets. The next step for the HET team is to complete commissioning of the telescope. Then the team will move on to commissioning HET’s three new science instruments.

Larry Ramsey, chairman of the HET Board of Directors and professor at Penn State, remarked, “The revitalized HET will contribute to many areas of science — not only the study of dark energy; but the nature of dark matter; the first stars in the universe; starburst galaxies; massive black holes; and to the discovery, confirmation, and characterization of extrasolar planets.”

The Hobby-Eberly Telescope came online in 1997. It is a partnership between The University of Texas at Austin, The Pennsylvania State University, Georg-August-Universität Göttingen, and Ludwig-Maximilians-Universität München. The HET upgrade was funded by a combination of federal, state, and private sources.

— END —

Media Contact: Rebecca Johnson (McDonald Observatory PIO); 512-475-6763

See published news release with more photos.

Texas Astronomer Solves Mystery of 'Born Again' Stars with Hubble Space Telescope

by Rebecca Johnson

AUSTIN — University of Texas astronomer Natalie Gosnell has used Hubble Space Telescope to better understand why some stars aren’t evolving as predicted. These so-called “blue stragglers” look hotter and bluer than they should for their advanced age. It’s almost as if they were somehow reinvigorated to look much younger than they really are.

Though blue stragglers were first identified 62 years ago, astronomers have yet to converge on a solution for their odd appearance. The most popular explanation among several competing theories is that an aging star spills material onto a smaller companion star. The small star bulks up on mass to become hotter and bluer while the aging companion burns out and collapses to a white dwarf – a burned out cinder.

To test this theory Gosnell’s team conducted a survey of the open star cluster NGC 188 that has 21 blue stragglers. Of those, she found that seven had white dwarf companions, by identifying their ultraviolet glow that is detectable by Hubble.

Of the remaining 14 of the 21 blue stragglers, a further seven show evidence of so-called mass transfer between stars in other ways. Gosnell said she believes these are older white dwarf-blue straggler binaries, and indicate two-thirds of blue stragglers form through mass transfer.

“This was really great,” Gosnell says. “Until now there was no concrete observational proof, only suggestive results,” Gosnell said. “It’s the first time we can place limits on the fraction of blue stragglers formed through mass transfer.”

This discovery sheds light on the physical processes responsible for changing the appearance of 25 percent of evolved stars. Gosnell’s work, which closes gaps in our understanding of how stars age, is published in the current issue of The Astrophysical Journal.

The problem came to light because in recent years, astronomers have been able to make a complete and accurate census of stars in a number of open star clusters, Gosnell said.

“Open clusters really are the best laboratory for the study of stellar evolution,” Gosnell said. “They have a simple stellar population.” The stars in a cluster form at the same time and from the same materials, she explained.

The cluster population studies revealed that up to a quarter of the oldest stars “are not evolving like we think they’re supposed to,” Gosnell said. Stars that astronomers expected to become red giants (like Aldebaran, the eye of Taurus, the bull) instead became “blue stragglers,” unexpectedly bright, blue stars with a host of strange characteristics.

Gosnell wanted to find out what happened to them. So she, along with Bob Mathieu at the University of Wisconsin-Madison and their collaborators, designed a study using Hubble Space Telescope’s Advanced Camera for Surveys to try to differentiate between three theories of how these stars became blue stragglers.

The theories included: collisions between stars in the cluster (with debris coalescing to form a blue straggler), the merger of two of the stars in a triple star system, or mass transfer between two stars in a binary pair.

In a binary pair of stars, the larger star will evolve faster, Gosnell said. That star becomes a red giant. A red giant is so bloated that the outermost layers of gas on its surface are only tenuously held by the star’s gravity. They can be pulled off by the gravity of the companion star. This is mass transfer.

As the gas is siphoned off by the partner, the red giant is left with only its core, making it into a white dwarf. The partner — initially the less massive of the pair, but now the heavier one — becomes a blue straggler.

Gosnell’s method is limited by the fact that it will not detect white dwarfs that have cooled down enough so that they don’t glow in UV light detectable by Hubble, she said.  That means that only those white dwarfs formed in the last 250 million years (youngsters, astronomically speaking) are detectable.

Knowing more about how these stars form is important because astronomers use their assumptions to model the stellar populations of distant galaxies (where the light from all the stars blends together). “You don’t want to be ignoring 25 percent of the evolved stars” in those galaxies, Gosnell said.

Such models are important because distant galaxies figure into many different types of cosmological studies. Right now, Gosnell said, “the models have a lot of room for improvement.”

“If we tweak the way models treat mass transfer, that would bring the observations and theory together,” Gosnell said. “They would agree. And we can use this to inform our understanding of unresolved stellar populations” — that is, those stars in galaxies so far away that all their light is blended together.

Gosnell plans to continue studying these stars using the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory and its IGRINS spectrograph to constrain the number of blue stragglers that could form through mergers in triple systems.

— END —

Media contacts:
Rebecca Johnson, UT Austin McDonald Observatory: 512-475-6763
Ray Villard, Space Telescope Science Institute: 410-338-4514

Science Contact:
Dr. Natalie Gosnell, W.J. McDonald Postdoctoral Fellow, UT Austin McDonald Observatory: 512-471-3423

See published news release with more photos.

Education & Outreach

McDonald Shines on Solar Viewing Upgrades

by Frank Cianciolo

This video of a solar flare was taken on Oct. 14, 2015 at McDonald Observatory using a six-inch telescope with a hydrogen alpha filter. (Kevin Mace/McDonald Observatory)

 

If someone mentions viewing the Sun, what first comes to your mind? Wearing a cardboard box over your head looking at a tiny pinhole-projected image? Viewing the photosphere with a white-light filter mounted at the front of your telescope? Stunning images from space-based solar telescopes? If your first thought wasn’t the Solar Viewing at McDonald Observatory, you just might be in for a treat.

It wasn’t that long ago that our white-light views showed mostly featureless sunspots, and the rest of the surface looked mostly blank white. However, images taken from McDonald Observatory’s Solar Viewing system now show an amazing level of detail — comparable to images taken by the Solar Dynamics Observatory (SDO) from space — despite being taken through the Earth’s atmosphere.

These side-by-side images of the white light Sun taken on December 26, 2015 by the Solar Dynamics Observatory (SDO) from space and from McDonald Observatory's most recently upgraded Solar Viewing system are surprisingly comparable. (SDO/NASA, Kevin Mace/McDonald Observatory)

The most recent upgrades to the Solar Viewing system have advanced the Frank N. Bash Visitors Center (VC) solar imaging capabilities to a point not dreamed of even three or four years ago, much less 14 years ago when the VC opened. While the Visitors Center is most well known for the nighttime views afforded during well-attended evening Star Parties at the Helen S. Martin Star Amphitheater and the Rebecca Louise Gale Telescope Park, the excellent twice-daily “Solar Viewings” of our nearest star are not to be missed.

McDonald Observatory has been hosting Solar Viewings since the W. L. Moody, Jr. Center opened its doors in 1981. Early programs consisted of projecting an image of the photosphere through an 8-inch Celestron Schmidt-Cass onto an approximately 8-inch paper screen with a staff member commenting on any visible sunspots. In the early ‘90s, the Moody Center acquired a Hydrogen-alpha (Hα) filter, which allowed routine viewing of sunspots, prominences, spicules, and occasional flares if you knew what to look for and if you knew how to navigate a relatively dim red image while surrounded by bright sunlight. Typical visitors were mostly lost.

Then, longtime friend and Houston amateur astronomer Lloyd Overcash made a gift of an off-the-shelf video surveillance camera and sundry adapters. Soon, Solar Viewing participants were treated to live views of impressive chromospheric features easily seen by all on bright television screens. There were still a few drawbacks, however. In addition to visitors needing to stand uncomfortably throughout the program, sunlight streaming through the dome shutter frequently caused bright glare on the television screens or, worse, in the eyes of those unfortunate enough to have to stand in the opening. Also, the setup offered only one rather highly magnified view.

With the construction of the Frank N. Bash Visitors Center (VC) and its multimedia theater, new possibilities presented themselves. 2016 Board of Visitors Staff Excellence Award winner Kevin Mace was just the person to bring those possibilities to life. Fiber optic cables and video converters brought live views from a pair of telescopes — one Hα filtered, the other white-light filtered — into the VC’s 12-foot wide screen. The telescopes could be remotely controlled, with animations, time-lapse video, and access to the latest images available online. Best of all, participants could sit comfortably in the theater out of the glare of the Texas sun. Except...

Those live images that had looked fine on 21-inch tube-type TV screens were now seen to be somewhat lacking when enlarged to fit a 12-foot screen. Mace began a quest for better video cameras and has continued to equip the Solar Viewing system with the latest and best equipment possible. Early donations from the Semmes Foundation helped the VC procure higher-resolution remote-controlled cameras that allowed far better viewing of various solar features. Later donations, also from the Semmes Foundation, added a wide-field “full disk” Hα view to contrast with the existing “full disk” white-light, and more highly magnified Hα views.

Las Cumbres Observatory founder Wayne Rosing’s keen eye for optics noticed that the 14-inch Celestron Schmidt-Cass telescope providing the main Hα view could be improved, and he generously offered to replace the Celestron with a 6-inch AstroPhysics refractor, donated a 4-inch StarLight refractor to provide a detailed white-light view, and even provided a new pier designed and fabricated specifically for the VC’s use with the new refractors. Now the cameras, so appreciated just a number of years before for their enhanced views, needed replacement! Once again, the Semmes Foundation stepped up. After these most recent upgrades, Rosing stated, “The McDonald image is just about the best I have seen. Clearly Mt Locke has excellent morning seeing, which is often the key for great solar observing. I am very pleased to see first hand the quality of the images produced by the telescope we donated.”

The Visitors Center, always a work in progress, will no doubt continue to add improvements to its Solar Viewing system, through generous supporters and through income generated by the VC’s dramatically growing visitation. The daytime Solar Viewing is often the most inspiring and hands-on experience gained by students who visit McDonald Observatory on day trips from local rural areas, and these programs are a very important part of the education and outreach mission.

On a recent afternoon visit to the Visitors Center, Board of Visitors member and Fort Davis resident Van Robinson was able to inspect the entire setup from front-end glass to video screen output, and every part in between. “The system Mr. Mace has masterfully assembled with the help of interested Board of Visitors members and other donors would certainly be the envy of the most advanced amateur astronomer and even, I suspect, a few solar researchers," he said. "The full-disk white-light images Kevin frequently generates with the setup rival those posted on NASA’s Solar Dynamics Observatory website. That all this was done to allow the public to see and learn about our Sun is just one of the many things that makes McDonald Observatory such a special place.”

Other images from McDonald Observatory solar viewing system are: comparison of three cameras; comparison of old and new Semmes cameras; sunspots, flares and filaments; solar prominence. Other available videos: quiescent solar prominence; eruptive solar prominence.

Spotlight

Bill Wren’s Passion Preserves the Night Sky

by Taft Armandroff and Sandra Preston

Preserving our beautiful and astronomically significant dark West Texas skies is a priority for McDonald Observatory, whose most passionate and effective advocate for astronomy-friendly lighting is Bill Wren. We are proud that Bill received the Hoag/Robinson Award from the International Dark-Sky Association (IDA) in November 2015. The award, named for Dr. Arthur Hoag and William T. Robinson, who both pioneered outdoor lighting control, is given to an individual who has been outstanding in educating governmental organizations, businesses, and the public about the merits of outdoor lighting control ordinances.

For the past 20 years, Bill has worked with city councils, county governments, utility companies, media representatives, and businesses across West Texas and beyond to promote good lighting solutions that safeguard dark skies while at the same time improving safety, cost efficiency, and environmental protection. Bill was recently featured on the CBS News “Sunday Morning” program, where he was referred to as “the Angel of Darkness” due to his efforts to protect the night skies of West Texas, one of the darkest spots on the globe. Bill has also helped McDonald Observatory to organize and facilitate a series of dark sky preservation and sky interpretation workshops for Texas Parks and Wildlife rangers, greatly leveraging the support from the late Board of Visitors and Orion Circle member, Joe Orr, to inspire the public to appreciate and preserve this important natural resource.

On February 16, 2016, the Railroad Commission of Texas issued a formal notice reminding the operators of oil and gas rigs in the vicinity of McDonald Observatory of the law and best practices in outdoor lighting, as well as the need to minimize lighting impacts. Included in the notice is a link to McDonald Observatory's Dark Skies Initiative and an important report written by Bill Wren and Board of Visitors member Stacy Locke of Pioneer Energy Services that scientifically documents how lighting intervention and adjustment using best practices creates win-win situations for all concerned. The release of this notice is the result of a meeting at the Railroad Commission late last year that included Bill Wren, Joel Barna, Board of Visitors member Debbie Dorsett, and Taft Armandroff.

This is just one recent example of how Bill’s tireless efforts have spread far and wide to raise awareness and help protect the dark skies of West Texas and beyond. He has made continuing astronomical research possible at McDonald Observatory, defending millions of dollars of investment. In addition, he has preserved the night skies for the general public. Due to his outstanding work, many laws and zoning rules have been updated to protect the nighttime environment for future generations. Bill has set a high standard for all of us, and his outstanding dedication to night sky preservation is greatly appreciated.

Featured Image

Alexanders Ring the Rocks at GMT Groundbreaking

Alexanders Wield Golden Hammer at GMT Groundbreaking

by Carolyn Porter

In a large white tent shaken loudly by the Atacama Desert wind, Chilean President Michelle Bachelet welcomed an international contingent of scientists, researchers, governmental officials, and supporters during the formal construction groundbreaking ceremony of the Giant Magellan Telescope (GMT), held on November 11, 2015 at the Las Campanas site.

McDonald Observatory director Taft Armandroff and Board of Visitors member Wayne Alexander formally represented McDonald Observatory in the celebration of this important milestone. Taft Armandroff serves as chair of the Giant Magellan Telescope Organization (GMTO) board of directors, and Wayne Alexander serves on the GMTO board.

Although the Las Campanas site in the Chilean Andes was chosen for a combination of beneficial factors that include dark skies, dry air, and access to Southern-hemisphere skies, the site was named “Las Campanas” — which means “the bells” in Spanish — because of the unusual sound of the local rocks when struck. Following the speeches, Wayne Alexander and his wife Barbara joined other GMTO representatives in striking the rocks with a golden hammer to make them ring like a bell.

Once constructed, the GMT will provide the sharpest possible images from its seven 8.2-meter mirror segments, four of which have been cast at the University of Arizona. Creating a mirror that is roughly eight stories tall, the assembled GMT mirror segments will have a light-collecting surface that is more than twice as wide as existing optical scopes. The GMT will commence scientific activity as soon as possible after only four of its seven mirrors are set in place.

If you are interested in learning more about opportunities to become involved with the Giant Magellan Telescope, please contact Carolyn Porter, director of GMT development at 512-471-1305 or cporter@astro.as.utexas.edu.

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