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Jun 29, 2012

Observatory Exposes JMU Astronomers to What They Can't See

Video by Kelly Abbott


Reflections

Ashley Lauren Schaper, vice president of the JMU Astronomy Club, on her third trip to the observatory: "Being at Green Bank, I'm constantly reminded just how massive our universe really is. Over the years, science has achieved so much, and yet there is never an end to the things we don't know."

William Alexander: "(The students) got to have an experience where they were immersed in astronomy. So it wasn't just a lab that you spend one or two hours in and then leave. I mean, we were here for two whole days."

Chris Wolfe, on his first visit to Green Bank: "This trip has reminded me how intricate our own galaxy is. Not only are we revolving around the sun, but our entire solar system is revolving around the galactic center of the Milky Way. It seems like there would be so much chaos and countless collisions within the Milky Way when considering the hundreds of billions of stars that could possibly contain planets of their own, but the physics ends up making everything work out nicely."

What do we already know about our galaxy?

The 26 JMU students who traveled to the National Radio Astronomy Observatory in Green Bank, W.Va., Oct. 2-4 blurted out ideas, most of which are widely accepted by the astronomic community:

  • The Milky Way galaxy is a barred spiral 100,000 light years across.
  • All stars and gases in the galaxy are concentrated on a broad, flat disc.
  • There is a huge black hole at its center, and our solar system is two-thirds of the way out from that center.

"Here we have a list of supposed facts, facts that we're taught; they're in our textbooks," Sue Ann Heatherly, an education officer at the observatory, explained to the classroom full of astronomy enthusiasts. "But I find it amazing that we can even make this list at all, given that we are embedded in this thing called the Milky Way galaxy. I mean all of our telescopes are located on Earth, and so trying to figure out what the galaxy looks like—how big it is and so on—has been a really daunting task over time."

Heatherly makes an interesting point. How can we possibly know what our galaxy looks like as a whole, when we are looking from within that galaxy? How can we prevent what we can see from limiting what we can know?

The short answer is spectroscopy. According to the Research GATE scientific network, spectroscopy uses the Doppler Shift—wherein the velocity of the observer and the source must be considered in observing light and sound waves—to distinguish the properties of distant stars and galaxies, including their motion and chemical composition. Spectral data gathered by radio telescopes can also detect the presence of gases, and their motions, within the galaxy.

Since digital telescopes only detect objects that can be seen by the eye, like stars and planets, researchers need a radio telescope—a big one—to gather this information.

The Project

"You will use the telescope like a spectrometer to search within our galaxy for clouds of hydrogen gas by tuning the telescope to the right frequency, the frequency at which atomic hydrogen emits radio waves," Heatherly explained to the students. "You're not going to be looking at stars. You won't be looking at ionized gas. You're not going to be looking at nebullae like the Orion nebullae. You're looking at the cold atomic gas out of which all this stuff forms."

The group used a 40-foot-wide radio telescope, solely designated for educational endeavors since 1987, to gather spectral data. Looking in multiple directions, students mapped the Milky Way by highlighting clouds of atomic hydrogen to reveal the spiral nature of the galaxy.

William Alexander, assistant professor of physics and astronomy and director of JMU's John C. Wells Planetarium, explained how we can "see" the galaxy using spectral data.

"Basically, clouds of hydrogen gas give off very specific wavelengths, one of which is given off in the radio part of the spectrum," said Alexander, who made the trip with members of the JMU Astronomy Club and a few select astronomy students. "If clouds of gas are moving either toward you or away from you, they will either be blue-shifted or red-shifted, effecting where the clouds will show up on the spectrum."

Spectral data allows researchers to go beyond the visible realm of the universe, which is heavily influenced by perspective and visual confirmation, to develop theories about the galaxy in which we live.

"There is a lot to be learned from studying wavelengths of light that our eyes cannot detect," said Patrick McCauley, president of the Astronomy Club. "Modern astronomy is 400 years old this year, but it wasn't until 80 years ago that we began utilizing new wavebands and this is something that the public doesn't always understand."

The JMU group worked in the telescope control room through Friday night and into the wee morning hours of Saturday, reading spectral lines and analyzing printouts. Chris Wolfe hadn't expected to still be awake at 5 a.m. scanning the galaxy for gas clouds, but he didn't have much trouble staying up.

"Seeing the different peaks of neutral hydrogen drawn as it rolls off a chart recorder at 2 in the morning is an amazing thing to witness, as you are essentially seeing the Milky Way's spiral arms moving," Wolfe said.

The students completed step one of their research project at Green Bank, which was to gather quantitative spectral data about the Milky Way. Step two, analyzing the data and drawing conclusions, will be finished in class over the next few weeks.

Green Bank, W.V.

Located about two hours southwest of Harrisonburg, the NRAO at Green Bank is home to the world's largest fully steerable radio telescope. Named the Robert C. Byrd Green Bank Telescope, the instrument is more than 100 meters wide and its massive white structure towers over the rural landscape.

The observatory houses five other radio telescopes, including the 40-foot educational telescope used by the JMU students. Green Bank is an ideal location for this technology because there is very little radio interference from the local population.

"There's really nothing there," Alexander said.

McCauley, the Astronomy Club's president, worked at the observatory over the summer.

"The observatory is centered in the National Radio Quiet Zone, where cell phone towers are prohibited, wireless devices of nearly all sorts are strictly regulated, and even faculty appliances are hunted down on an individual basis because they can interfere with the telescopes," McCauley said.

Alexander said a team employed by the observatory identifies and fixes stray radio noises, like a malfunctioning microwave oven or a short-circuiting dog blanket.

"They go around in a truck with a directional antennae and find out where the stray frequency is coming from, and they buy the owners a replacement product that works properly," he said.

 

Published October 2009








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