Tucked away amidst the rolling Allegheny Mountains, Green Bank is home to one of the world’s premier astronomical observatories. There, radio telescopes tune in to the whispers of the universe, night and day. It’s a place unlike any other on Earth.
The expansive grounds of Green Bank Observatory are dotted with what appear to be eight oversized satellite dishes, the largest with a dish bigger than a football field and taller than the world’s highest roller coaster. Instead of receiving TV signals, these dishes detect radiation from objects in space in the form of radio waves. Invisible to the human eye, radio waves travel from distant stars and galaxies and pass through Earth’s atmosphere to the ground, where they are collected by radio telescopes. From there, these radio signals are decoded by scientists eager to learn more about our universe.
Some of Green Bank’s radio telescopes have graced the grounds since 1958, shortly after the National Science Foundation selected Green Bank as the site of its new radio astronomy observatory. These venerable telescopes are joined by the crown jewel of the observatory: the 328-foot-diameter Green Bank Telescope (GBT), which celebrated its twentieth birthday last summer.
With a dish area of 2.4 acres, the GBT is the largest fully steerable radio telescope in the world. The GBT’s massive metal support structure can rotate and tilt, allowing the telescope to point in almost any direction. It’s also exceptionally precise—the GBT can resolve fine details equivalent to discerning the presence of a quarter at a distance of three miles. It does this using two thousand tiny motors that gently press on the thin aluminum panels lining the dish to maintain the dish’s shape.
The GBT’s size and precision makes it great for studying faraway galaxies, but it’s also sensitive to radio waves generated by nearby objects, like refrigerators, vacuum cleaners, Bluetooth devices, and vehicles. “So many things have that technology that can cause interference baked in now,” said Jill Malusky, public relations specialist at Green Bank Observatory. If the GBT can detect a signal from a galaxy millions of light-years away, “imagine how bright of a signal your cell phone sitting next to it is going to be,” says Amber Bonsall, a scientific data analyst at Green Bank Observatory.
Because interference can be extremely harmful to radio astronomy, the remote town of Green Bank, population 182, was the perfect place to establish an observatory. To protect the observatory from radio interference, the Federal Communications Commission, a government agency that regulates radio, cable, and satellite communications, established the National Radio Quiet Zone around the observatory in 1958. This 13,000-square-mile expanse restricts human-made radio transmissions and extends into Virginia and western Maryland.
While residents near the perimeter of the Quiet Zone probably don’t notice any restrictions, the restrictions become progressively more stringent closer to the observatory. At Green Bank, there are no microwaves, no cell service, and no Wi-Fi. “We always joke that it’s like living in the 1960s,” said Bonsall, who lives on site. She has an old-school landline—stretchy spiral cord and all—and her cell phone is essentially a “glorified alarm clock.”
Many Green Bank residents, including Bonsall, happily give up cell service and Wi-Fi to live in such a peaceful place and to be part of some of the biggest discoveries in the history of astronomy. “It’s a very odd experience because most people are like, ‘I can’t live without my cell phone!’ It’s amazing how quickly you get used to not having it,” she said.
From identifying a black hole in the Milky Way to the search for extraterrestrial life, Green Bank Observatory provides scientists and West Virginians an extraordinary view of the universe.
A Black Hole Bombshell
In the early 1970s, Green Bank was the place to be for radio astronomy. Scientists from around the world used the telescopes to discover a dense, rapidly spinning object called a pulsar in the remains of an exploded star, find molecules in interstellar space, and measure the rotation of galaxies outside our own. These discoveries helped us understand what happens at the end of a star’s lifetime, showed us that molecules—including those important for life—are common in our galaxy, and led to our current understanding of dark matter, a difficult-to-detect form of matter that scientists believe makes up 85 percent of our universe.
Bruce Balick, an emeritus professor of astronomy at the University of Washington, used the telescopes at Green Bank during this astronomical heyday. Balick and his research partner, Robert Brown, the former Deputy Director of the National Radio Astronomy Observatory, set out to observe clouds of gas where stars are thought to form, including one at the center of the Milky Way.
Despite the name, astronomers don’t typically listen to radio signals. Instead, the signals are recorded as squiggly lines on a sheet of paper, like an astronomical polygraph machine. (Today, a computer does the recording.) As Balick and Brown maneuvered the telescopes to observe different gas clouds, the signals were almost nonexistent. “Nothing, nothing, nothing, nothing. And then finally we went to [the center of the Milky Way], and POW!” said Balick. “My stomach ended up in my throat. This is amazing. This is nothing like we ever would have expected.”
The radio waves detected by Balick and Brown weren’t from an ordinary gas cloud. Instead, they were from a supermassive black hole, containing more than four million times the mass of our Sun, lurking at the center of our galaxy. The discovery turned black holes from science fiction into fact, and scientists have since found even larger black holes at the centers of other galaxies. In 2019, astronomers took the first-ever picture of a supermassive black hole in a galaxy over 50 million light-years away, using a network of radio telescopes all over the world—including those at Green Bank.
Ice Storm vs Giant Telescope
Scientists also use the telescopes at Green Bank to observe objects a little closer than the Milky Way’s center. As robotic landers and rovers make their way from Earth to their destinations across the solar system, radio telescopes around the world keep tabs on their journeys. Most recently, the GBT tracked NASA’s Perseverance Mars rover as it made its final descent to the Martian surface in February 2021.
In true West Virginia fashion, the weather did not cooperate. The morning of the landing, a snowstorm enveloped the observatory. Although the snow wouldn’t affect the radio signal itself, piles of heavy snow can deform the panels of the dish, altering the signal and preventing researchers from observing the rover’s landing on Mars.
In the hours leading up to the landing, the operators instructed the telescope to follow the Sun as it moved across the sky, hoping that the faint warmth would melt the snow. Intermittently, they nodded the GBT’s massive head as far toward the ground as possible—into the so-called “snow dump” position—to get rid of any snow in the dish. Usually, the GBT would start tracking the rover hours before landing, but for the safety of the telescope it was critical to continue the snow dumping routine and delay the observations as long as possible. “Even then, it was a possibility that, because of the weather, we weren’t even going to be able to do it,” Bonsall said.
With the countdown clock ticking, the GBT locked on to the signal from Perseverance. Bonsall and Green Bank scientist Will Armentrout monitored the signal as Perseverance entered Mars’s atmosphere and began its harrowing seven-minute journey to the surface. When Bonsall tracked the InSight Mars lander in 2018, the room was packed with other members of the Green Bank observatory team, scientists from NASA, and even Boy Scouts. But on the day of Perseverance’s landing, it was just Bonsall and Armentrout, masked and six feet apart. “It was really, really nerve wracking,” said Bonsall. “We sat there in complete silence for a good five minutes, and at one point one of us said “did it land?””
Finally, a small bump appeared in the signal, indicating that Perseverance had touched down. For a few brief moments, Bonsall and Armentrout were the only people in the world who knew that Perseverance had landed safely, except for a few scientists at the Effelsberg telescope in Germany who turned a radio eye to Mars as well. With its descent completed, Perseverance began its mission. The rover is searching for specific minerals and molecules on Mars’s surface and creating caches of promising samples. A future mission will collect these samples and return them to Earth, so scientists can study them to determine if the Red Planet ever hosted life.
Searching the Cosmic Haystack
While Perseverance looks for life on the surface of our planetary next-door neighbor, Green Bank astronomers are undertaking their own search for life beyond Earth. Since humans have the ability to transmit radio waves, many astronomers believe that other intelligent life in the universe could develop the same technology, making radio telescopes a good tool for the search.
In 1960, Green Bank astronomer Frank Drake undertook the first ever radio search for intelligent extraterrestrial life, sifting through the cosmic haystack in search of unusual signals that may indicate other intelligence. He pointed a telescope at two nearby stars for 150 hours over the course of a few months. The search came up short, but it led to a conference at Green Bank where a group of astronomers, including Carl Sagan, gathered to discuss the search for extraterrestrial life. The conference centered around the Drake Equation, a mathematical formula that estimates how many potential civilizations in the Milky Way might be able to communicate with us. Currently, estimates range anywhere from tens of millions of civilizations to just us, alone in the galaxy.
Today, the search for extraterrestrial civilizations continues with the Breakthrough Listen project, which relies on the GBT as well as the Parkes Observatory in Australia and the Automated Planet Finder Telescope in California. Since the project started in 2016, Breakthrough Listen has collected petabytes of data (equivalent to the capacity of several million CDs) from the million stars closest to Earth, the center of the Milky Way, and the hundred closest galaxies to ours. So far, the universe seems to be quiet. But if there’s someone or something out there that wants to be heard, Green Bank may be the first to know.
Memories of the Observatory
As the birthplace of American radio astronomy, Green Bank is a place of many superlatives and firsts, from the world’s largest fully steerable telescope to the one-of-a-kind Radio Quiet Zone that protects it. Every year, tens of thousands of visitors flock to Green Bank to get their astronomy fix and enjoy the lush, green mountains and brilliant, starry skies of Pocahontas County.
Professional astronomers from around the world make the pilgrimage to West Virginia to use the Green Bank telescopes, although increasingly many observe remotely. For those who get the chance to visit, the observatory evokes fond memories. “Anytime I come to the east coast, it is so tempting to rent a car and make the drive through the mountains,” says Balick. He and his wife cherished their time in Green Bank. “We loved the fact that everybody at the observatory was so friendly.”
Professionals aren’t the only ones who use the telescopes at Green Bank; students from all 50 states participate in the educational programs at the observatory. West Virginian middle schoolers attending the Governor’s STEM Institute spend two weeks in the summer bunking in the observatory dormitory and learning about radio astronomy. These students get a rare chance to engage in astronomy research by designing a project, collecting data, and preparing a proposal to be granted observing time on the GBT. When students aren’t working on their research projects, they can go hiking, mountain biking, and spelunking in the surrounding mountains.
In 2006, I was one of those middle schoolers. I woke each morning to the Rhododendron Song blaring in the bunkhouse, watched the telescope’s recording pens write the story of the Milky Way, and spent hours scrutinizing data. Looking back on it now, I’m stunned that they let a bunch of eighth graders use one of the largest telescopes in the world. The experience didn’t quite turn me into a radio astronomer, but it did set me on my current path as an astronomy graduate student. Whenever Green Bank is mentioned in conference talks or seminars, I feel a quiet spark of joy. How lucky West Virginians are to have a connection to Green Bank, a place that connects us, in turn, to the universe.
Kerry Hensley is an astronomy PhD candidate and science writer in Boston, where she tells anyone who will listen about how great the stars are in West Virginia.