September 17, 2000|By Stephanie Fletcher | By Stephanie Fletcher,SPECIAL TO THE SUN
Driving through Deer Creek Valley in mountainous eastern West Virginia, I came upon an amazing sight. A charming red barn with a silo stood in the foreground and a green alpine meadow spread out around it in all directions.
Nothing unusual about that. But what was that huge, futuristic structure in the background towering above the tree line?
I soon discovered that the titanic form looming on the horizon near the tiny farming community of Green Bank was the largest fully steerable radio telescope in the world. The colossus became operational last month and will soon begin collecting radio waves from space.
Although one might think such governmental space-gazing might be top-secret and hush-hush, this National Radio Astronomy Observatory site is open to the public and even provides free tours.
Radio telescopes do not look or act like telescopes that use lenses. The instruments feature large, shallow dish antennae. Instead of registering sources of visible light, they gather radio emissions coming from space. After a computer processes the information, astronomers can create viewable pictures.
The Green Bank Telescope (GBT) is mammoth: taller than the Statue of Liberty and wider than a football field. It will be used for all sorts of useful scientific research, and it's possible that if there's intelligent life elsewhere in the universe, earthlings may first learn of it from this remote outpost.
The West Virginia site is one of three major telescope sites of the National Radio Astronomy Observatory. The observatory was created in 1958 by the National Science Foundation - a federal agency - for the purpose of exploring the universe.
Telescope facilities are operated by a consortium of nine universities. Two additional sites are in Socorro, N.M., and Kitt Peak, Ariz. The observatory's headquarters are in Charlottesville, Va.
Perfectly isolated
Deer Creek Valley was selected as a site because of its isolation. Also, the barrier provided by surrounding mountains protects sensitive receivers from radio frequency interference. A staff of 105 runs the Green Bank facility, which includes six large radio telescopes besides the GBT.
The 2,700-acre site consists of four main buildings, one of which is called the Tour Center and functions as a visitors center. The telescopes are spread out behind the buildings in vast, close-cropped meadows. Walkers and bikers are welcome to explore the grounds.
During a short lecture in the Tour Center, the audience learns that radio telescope receivers are frozen with liquid nitrogen to facilitate reception.
"Signals from space are often so weak that simply the heat of the electronics in the receivers overwhelms them," says Green Bank spokesman Michael Holstine. "We must freeze the electronics to a point where there is almost no molecular movement. We can reach a point about 4 degrees above absolute zero - the point where there is no molecular movement."
The presentation includes a demonstration of how the freezing property of liquid nitrogen effects gas molecules. A red balloon is shrunk to baseball size by liquid nitrogen and then slowly reinflated after it comes in contact with room-temperature air. Then the demonstrator splashes the frigid fluid on the carpet where it surges like a vaporous wave into the audience and then slowly dissipates. Kids will love this.
A slide show features colorized pictures of space oddities (quasars and evidence of black holes) gained from radio telescope technology.
After the indoor presentation, there is a guided tour of the facility. During the one-hour excursion, a 20-seat minibus travels along a service road and a guide points out several structures.
One highlight is a relatively small radio telescope - a forerunner of the titans currently in operation. Grote Reber, a radio physicist and a pioneer in radio astronomy, built the first dish antenna in his back yard in Wheaton, Ill., in 1937. Now it sits in a place of honor on the NRAO campus at Green Bank. Although imposing, the ancestor of the GBT has a diameter of only 32 feet - a pipsqueak compared with the giants there now.
Searching for life
Two other interesting instruments are an 85-foot telescope and a 145-foot telescope used by the folks from SETI: Search for Extraterrestrial Intelligence. When it was first introduced, radio astronomy was a new and exciting way of possibly detecting transmissions from beings from other worlds. Dr. Frank Drake, the first director of the observatory, conducted the initial SETI project in 1958.
The last SETI project at Green Bank took place in 1996. SETI searches for transmissions that do not appear natural, Holstine says.
When such a signal is found, "a protocol goes into effect which tests for repeatability. After a lengthy analysis process is conducted, if no explanation for the signal is forthcoming, it is identified as an `unknown source.' I think there are 56 unknown sources listed to date," Holstine says.
