Go to Green Bank to listen to the stars
Visitors to the West Virginia telescope get a close-up with the world’s largest movable land object
BIG LISTENER To eavesdrop on the universe, the Green Bank Telescope requires a quiet location with little interference from human-made radio signals.
NRAO, AUI, NSF
Long before we reached Green Bank, W.Va., the gleaming white dish of a massive radio telescope stood out against the lush green vegetation of a remote valley four hours southwest of Washington, D.C. By then, the car radio received only static, and our cellphones hadn’t gotten a signal in hours. To get even closer to the Robert C. Byrd Green Bank Telescope — the world’s largest movable land object — we were required to turn off those useless phones and our digital cameras.
“The big battle we have here is to prevent any interference from getting to our telescope,” says Steve White, leader of the telescope’s microwave engineering group.
Many objects in the universe, such as quasars and clouds of hydrogen gas, give off radio waves, but they are weak and easily overwhelmed by human-made radio signals. That is why the telescope is in such a remote spot with strict rules about electronic equipment that could interfere with signals. Several rooms in the facility, including the telescope’s control room, are encased in copper mesh, creating big Faraday cages that prevent stray signals from escaping toward the telescope’s detectors. Even the microwave in the public café has shielding (SN: 5/16/15, p. 5). “We don’t want to self-interfere,” White says.
Standing taller than the Statue of Liberty, the telescope is the highlight of the facility’s hour-long bus tour. The instrument’s dish is bigger than a football field, but it’s nearly impossible to get a sense of just how big it is until the bus drops us at the fence surrounding it. We can then see the 2,004 aluminum panels that make up the huge dish, each one about the size of a queen mattress and individually adjustable to ensure the telescope’s accuracy. From our driver, we learn about recent discoveries, such as a white dwarf star so cold it had crystallized into an Earth-sized diamond. The tour also includes tales of annoying radio interference, including when the U.S. Fish and Wildlife Service released radio-tagged flying squirrels in the area.
The telescope’s science is not cheap. While touring the facility’s high-tech labs, White showed us custom-made gold-plated pieces inside the telescope’s detectors and talked about the sophisticated computer programs that focus the dish. “We’re trying to point something the size of a battleship with the accuracy of a wristwatch,” he says. But it’s only through such efforts that we can search for mysteries of the universe that we can’t even see.
