Green Bank Observatory Science Center The Robert C. Byrd Green Bank Telescope (GBT) is the worlds largest steerable telescope, standing 485-feet tall, weighing over 17 million pounds, with a 2.3 acre surface. The 140- foot (43-meter) telescope has the world’s largest ball bearing inside, measuring 17 1/2 feet and 150 tons. The Green Bank Observatory occupies over 2,600 acres in the Deer Creek Valley, surrounded by the Allegheny Mountains. The Green Bank Observatory welcomes over 3,500 students on site each year for tours, field trips, and camps. students in front of the GBT Image of the Magellanic Cloud Photo Source: S. Brunier; Design & Illustration: P. Vosteen Credit: Bruce Campbell, Smithsonian’s Air and Space Museum, GBT Green Bank Observatory/AUI/NSF, Arecibo Observatory. A ribbon of ammonia — a tracer of star-forming gas — in the Orion Nebula as seen with the GBT (orange). Background in blue is a WISE telescope infrared image showing the dust in the region. GBO/AUI/NSF