Star Power

A new telescope sets its sights on blue heaven.

by Jason Smith

Want to see a bunch of astronomers wired like kids on Christmas morning? Want to see them on cloud nine, in seventh heaven, and — work with me here — with stars in their eyes? Tell them they can design and build a world-class telescope. Then go away and let them do it.

The astronomers in Carolina's Department of Physics and Astronomy, with a little help from their friends at the National Optical Astronomy Observatory, Michigan State University, and the countries of Brazil and Chile, have spent the last eighteen years cooking up a high-tech telescope called SOAR (Southern Astrophysical Research). They've thrust the thing far into the sky in the foothills of the Chilean Andes.

It isn't the biggest telescope on the planet, but SOAR just might prove one of the world's most productive. It will capture the highest-quality images of any observatory in its class in the world. It will be more versatile and efficient than most telescopes. And Carolina's astronomers will be able to point it wherever they like without ever leaving Chapel Hill. With SOAR, Carolina plans to become a key player on the global astronomical scene.

Near the Top of the Bottom of the World

Cerro Pachon is a dusty, nine-thousand-foot desert mountain about thirty miles east (as the condor flies) from the town of La Serena on Chile's Pacific coast. Down in La Serena, all the taxis, stray dogs, and uniformed schoolkids running around make the place seem busy. But up on Pachon, it's absolutely silent, and your neighbors come in two flavors: mountains (with Pachon's sister foothills nestling all around and the Andes proper piling up in the distance) and telescopes (from Pachon, you can't see anything man-made that doesn't have to do with astronomy). SOAR's clean white dome looks a little improbable up here, like a gigantic golf ball dropped in the desert.

Why Chile? Well, the Southern hemisphere has fewer telescopes than we have up north. And astronomers, as the bumper sticker says, do it all night. They need clear, dark skies. The Chilean coast has relatively few cloudy nights, little rain, and not much ambient light from cities and towns. Add to that the center of the Milky Way galaxy passing right overhead, and Chile becomes an astronomer's heaven.

The view from Cerro Pachon. Photo by Gerald Cecil. Click to enlarge.

Looking into the Big Glass

SOAR moves like a battleship gun: the entire dome can rotate, and the four-meter mirror can move up and down. The mirror itself is about four inches thick and polished to a slightly aspherical shape (to a tolerance of about seven billionths of an inch). It's supported by pads connected to 120 electric motors, which can independently push and pull the mirror from below so that it keeps the same shape no matter which way it's pointed (seven thousand pounds of glass act weird when you start moving them around). The mirror's reflectivity — and to some degree, the telescope's effectiveness — depends on an aluminum coating only three millionths of an inch thick. In fact, you could say that the $30 million, one-hundred-ton SOAR telescope is really just a skeleton to hold a couple tenths of an ounce of aluminum — a few pennies' worth — precisely where it needs to be. SOAR's reflectivity at this primary mirror is around 91 percent, about the best the astronomers could have hoped for.

When it comes to images, SOAR delivers. There's a trade-off in telescope design between the amount of viewable sky and the quality of the resulting image. Generally, the more sky you can see, the poorer the image quality. SOAR captures relatively small slices of the sky at very high image resolution. It can detect celestial objects about a billion times fainter than the naked eye can see.

SOAR is quick on the draw, too. For light to be useful to astronomers, the telescope needs to pass it through one of several instruments — such as a spectrograph or an infrared camera — which process the light in various ways. At many other telescopes, changing an instrument takes hours or even days. But SOAR's eight different instruments are set up like a railroad switchyard, allowing astronomers to redirect light to any one of them within a couple of minutes.

The Homesteader

Wayne Christiansen's grandparents emigrated from Denmark and settled in Fort Collins, Colorado. In exchange for working on a government irrigation project — Christiansen's grandfather dug, and his grandmother cooked for the workers — the couple settled on a plot of land near the water lines, knowing it would be fertile. They built a cattle farm that's still in the family today.

When I catch up with him in Chapel Hill, Christiansen is about to head out to Fort Collins for a few weeks' work on the farm. He'll stay in what the family calls the little red house, a one-bedroom cabin that "doesn't have a full-fledged, female-approved bathroom," as Christiansen puts it. ("It does have running water," says Christiansen's wife, Judy. "That's the only reason I put up with it.")

At sixty-three, Christiansen has the look of someone who might have been a high-school sports standout, and you can read the farm work in his hands and face. Among other things, Christiansen studies the movement of galaxies — how fast and in what direction they're going. The universe is expanding — faster and faster, as astronomers recently found out — and most galaxies can generally be said to be moving away from us. Christiansen combines data from different kinds of telescopes, including radio, X-ray, and optical, to build up a clear idea of what a galaxy cluster such as Abell-3128 is up to.

In 1986, when Chancellor Christopher Fordham encouraged faculty to come up with high-profile research projects, Christiansen swung for the fences. He went immediately to Bruce Carney, Carolina's only other astronomer at the time, and told him — chutzpah firmly in place — that they should build a telescope. Eighteen years later, Christiansen is ready to SOAR.

The ability to get data from SOAR as astronomical phenomena happen will be worth its weight in gold for Christiansen. Typically, astronomers submit competitive proposals, up to a year in advance, for telescope time. Agencies such as the National Optical Astronomy Observatory then award time on the nation's telescopes. Even if your proposal is awarded, it might be months before you can get on a telescope. And you'd better hope for clear skies, and that nothing is happening that's more interesting than what you originally proposed to do. "You don't just go in and pop off a red shift," Christiansen says, referring to a measurement that tells astronomers a galaxy is moving away from us.

But now Christiansen can pop off red shifts — and blue shifts, and almost anything else he cares to look for — on one of Carolina's 124 half-nights per year of observing with SOAR. Like his grandparents, he has settled in just the right place, and when all that light from long ago comes trickling down into SOAR, he'll be ready.

Wayne Christiansen and Bruce Carney with the SOAR telescope in La Serena, Chile. Photo by Jason Smith. Click to enlarge.

The Romantic

Astronomers will tell you that stars don't really twinkle. (It's just an effect caused by the earth's atmosphere.) So something else must be putting the sparkle in Bruce Carney's eyes. He's a bit of a romantic: he likes to point out that one of the agreements committing the university to SOAR was signed atop a pier that Joseph Caldwell built in 1824 to hold the university's first telescope. Carney wore the same necktie (printed with Van Gogh's Starry Night) to both the SOAR groundbreaking and the official SOAR dedication, which happened six years — to the day — apart. And when it comes to his research, Carney is fond of sticking close to home.

Carney studies our own galaxy, the Milky Way. Some of the Milky Way's oldest stars are near its center. All the dust between us and those stars makes them hard to see: in visible light, Carney says, they're three hundred thousand times dimmer than they are in infrared light.

So he attacks in infrared, where factors such as dust and moonlight don't make much difference. "Infrared astronomers are bottom-feeders," Carney jokes. "We're the catfish of the night. As long as we're getting light, we're happy." But by getting data on the temperature, brightness, and chemical compositions of our galaxy's stars, Carney can start to deduce their ages. "You can get some idea about whether the Milky Way took a billion years to form, or several billion years," he says.

The better the image quality, the more Carney can tell about the stars he studies. SOAR's images won't just be good, they'll be great — on the order of what the Hubble Space Telescope can do, if over a smaller field of view. SOAR's emphasis on image quality and aperture (the amount of light it can bring in) will make it a world leader in high-resolution astronomy images.

Carney remembers the day Christiansen had his big idea. Carney had a date that night: dinner at Crook's Corner with Ruth, to whom he's now married. He was excited to tell Ruth about the telescope over dinner. "She gave me neutrally positive comments about it," Carney says carefully, "but she was sort of inwardly rolling her eyes the whole time."

The Remote Controller

Gerald Cecil was SOAR's project scientist. But he'd be the first to admit that the control room down in Chile isn't going to knock your socks off. It's not 1950s sci-fi, he explains: no futuristic knobs or buttons, no glass balls buzzing with mysterious light. It's just a narrow room one floor below the telescope mirror, and it holds a handful of normal desktop computers and a TV monitor or two.

Then again, what you can't see from the control room is what Cecil is most proud of: SOAR's observatory, telescope, and instruments are controlled by computer systems more advanced than the control system of any other telescope on the planet. The programs that control SOAR are easy to understand, Cecil says, and they will adapt easily to changes that happen as SOAR's mission evolves.

Anyway, Carolina's astronomers won't mind the lack of whiz-bang in the control room up on Pachon — after all, they've got their own (see "The Undergraduate Behind the Controls"). They can be on SOAR and not at SOAR. Cecil made that happen.

"Really, when you're down in Chile, you rarely go upstairs to deal with your instrument," Cecil says. You merely deal with the stream of data it gives you, he explains, so you might as well do that in Chapel Hill. And when you need to know something about the sky or weather conditions, being five thousand miles away might just be an advantage. "Down there, the temptation is to just go out and look up," Cecil says.

But up on the big screen in Carolina's remote observing room, astronomers will "see" the cloud cover, the positions of the Milky Way and other celestial objects, and the weather conditions much better than they could with their own eyes in Chile. Their celestial targets will be superimposed on the night sky as it inches by. As the astronomers track these targets, they'll tell the telescope operator down in Chile how to react to the changing weather, cloud cover, and the moon.

Cecil's been working for years on outflows from galaxies. "Most of the motions in galaxies are boringly predictable," he says. "The stars go around the center in these one-hundred-fifty-million-year orbits, chug-chug-chug, living and dying, and some blow up, whatever."

But some galaxies intrigue Cecil a little more. He gets out a picture of galaxy NGC 3079, which has ejected a gigantic bubble of gas — about three thousand light-years across — that might be escaping NGC 3079's gravitational pull. That would send chemically enriched gas into contact with the primordial hydrogen of intergalactic space, which would theoretically affect the evolution of stars. But Cecil is just trying to learn why the gas flows as it does, and what causes these massive eruptions, called superbubbles.

Cecil wants to know if superbubbles occur in isolated galaxies, or if something has to alter the gravity of a galaxy — such as another galaxy passing nearby — before a superbubble can happen. Superbubbles are a crucial connection between the life cycles of stars and the evolution of galaxies, he says.

"And there are striking hints that the same sort of phenomenon is going on in our own galaxy," he says.

NEXT: "Within two minutes, I can get anywhere in the sky."

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