SOAR’s Chapel Hill Origins

Broadcast by: Jaclyn Lee; Written by: Alexa Phillips

In 1986, UNC Astronomy Professor Wayne Christiansen walked into the office of Bruce Carney, another astronomy professor, and suggested that they build a major telescope in celebration of the University’s Bicentennial.

The idea of a telescope was spurred by a piece of UNC’s history. In 1824, Joseph Caldwell, UNC’s first president, purchased the university’s first telescope. Seven years later, workers constructed the first astronomical observatory at an American state university, on Chapel Hill’s campus.

Following this event, there was a lull in astronomy at UNC until John Motley Morehead and the Morehead Foundation resuscitated the field in 1949. The Morehead Planetarium was endowed to the university, and the Morehead Observatory was completed 25 years later.

Carney and Christian were motivated by this legacy to revive the astronomy field at UNC and believed that building a state-of-the-art telescope would attract some of the best new faculty and students.

“A Carolina Bicentennial should be more than just looking at the past: it should be about strengthening the University’s mission of teaching and research,” Carney said.

The telescope project took off after major fundraising efforts and confirmation of viable partnerships among multiple universities and national governments.

After an 18-year-long process of developing and building, the Southern Astrophysical Research (SOAR) Telescope was completed in Chile in April 2004. The goal of the team was to further astrophysical research and assist with teaching and public outreach.

Carney and Christiansen chose to build SOAR in the southern hemisphere because of the ability to see the Milky Way galaxy and neighboring galaxies. There were also multiple similar-sized telescopes already built in the northern hemisphere.

 

“If you ask yourself where the most interesting things in the sky [are], most people think it’s anywhere in the sky. But the southern hemisphere is where the newest galaxies are…It’s where the center of the Milky Way galaxy itself is,” Carney explained.

In 1987, Christiansen decided the optimal location was in Cerro Pachón, a mountain in Chile that rises almost 9,000 feet above sea level. The area is far from population centers and free of light pollution.

The world of astronomy has changed tremendously because of the technology boom in the last two decades.

Gone are the days when telescopes consisted of small, narrow tubes with lenses that allowed people to see distant objects. The SOAR telescope is a massive structure housed within a dome-shaped observatory at the end of a winding dirt road atop Cerro Pachón. The observatory has a slit in the roof that astronomers open when they’re ready to use SOAR to observe.

SOAR stands out from traditional single-instrument telescopes because of its “quick change” instruments. Within minutes, astronomers can change from one instrument to another by just rotating a single mirror inside the telescope. Thus, if conditions change, astronomers are able to quickly react without their observations being interrupted.

The instruments give SOAR remarkable flexibility and allow astronomers to measure and observe a wide range of elements in the sky. In the past, only one instrument was mounted on a telescope, and a change of instruments could take more than half a day.

By maintaining two instruments – one optical and one infrared – that can be used with a simple movement of a mirror, astronomers maximize productivity and prepare themselves for unexpected events in the sky, such as a supernova.

Although Carney and Christiansen were responsible for the overall creation and development of SOAR, the University needed someone to orchestrate the building of one of the most important features of the telescope – the spectrograph.

In 1998, UNC hired Chris Clemens from the Cal Tech Astronomy Department with the task of building the integral instrument. While the dome and telescope axel were being created in Chile, Clemens began developing the Goodman High Throughput Spectrograph in Chapel Hill.

About 80 percent of the time astronomers observe with SOAR, they’re using the spectrograph because it disperses light to help measure detailed properties of the sky.

Sophisticated optical and infrared cameras on telescopes are quite heavy and complex pieces of equipment. Yet the real workhorse is the spectrograph because it aids in studying the spectra of stars, nebulae, and galaxies, which then helps astronomers determine their detailed chemical compositions and temperatures.

In order to study the detailed features of stars, astronomers have to take light apart into its various colors. The spectrograph was designed to be as blue-sensitive as possible because when a star is extremely hot, it emits more blue light. Many astronomers are looking at stars that reach more than 10,000 degrees. In comparison, the sun is below 7,000 degrees, so it appears yellow.

The astronomers need to see as much blue light as possible in order to observe these stars, and there are few instruments on Earth that are as blue-sensitive as the Goodman Spectrograph. SOAR’s exceptional image quality and optics are better than any telescope in its class.

“Most of what we do in astronomy is not really look at images of stars, because if you take the biggest telescope and look at a star, it still looks like a point. What you want to do is take the extra light you got by collecting in this big telescope, and spread it out into its colors, which we call a spectrum. And when you do that, now you see all kinds of things,” Clemens described.

The spectrograph was installed in SOAR in 2007 after nine years of continual work. It was a successful moment, but to this day, Clemens continues to make improvements on the instrument.

“There’s this moment when you look deeply into something and you have a special tool that you built, so you can see things for the first time that no one else knows. So the moment of scientific discovery that excites most scientists, that keeps them going, is when you learn something about this universe, and for a little bit of time, only you know that,” Clemens said.

The biggest struggle with the SOAR telescope was finding money to fund the project. The funding came from a public-private partnership, and the collaborators spent approximately $12 million from start to finish.

In addition to UNC, SOAR’s partners include the U.S. National Optical Astronomy Observatory, Cerro Tololo Inter-American Observatory, government of Brazil, Chile, and Michigan State University.

Each partner has guaranteed time each year for remote observations with SOAR. UNC receives 60 guaranteed nights per year to observe from Chapel Hill. Remote observing has been an effective and efficient way for astronomers to utilize the telescope for research and teaching.

“It’s very efficient to be able to do it from here, and technically it is perfectly okay…But emotionally, if you will, it’s not the same. It’s not the same as going on that pilgrimage to the mountain and going out on the mountaintop and seeing the sky and saying ‘I’m doing something big here,’” Christiansen said.

Astronomers in multiple countries are utilizing SOAR to study our galaxy in more detail, learn more about neighboring and new galaxies, measure distances and velocities of stars, and more.

Since the development of SOAR, there has been an addition of seven new faculty in astronomy and six in allied areas of physics at UNC.

“To me, that aspect of SOAR is a dream come true,” Christiansen expressed.

Clemens and UNC astronomy students are now using SOAR to study crushed up planet rubble. They utilize the spectrograph to determine what the material is made of and which elements are inside of the material, which ultimately helps astronomers determine the components of specific planets.

Carney and Christiansen put in years of relentless work to make their bicentennial epiphany a reality. Yet as they reflect on the experience and the triumphs, they say it was all worth every setback and every minute.

“We’ve only been able to see with our eyes, and now we can see and understand really how the universe largely works. How the solar system is running. We know there’s a lot more to be found…As I look at the history of astronomy, I’m amazed,” Carney said.

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