Picture from Google Earth
In a narrow vale between two folds of earthen ridges in eastern West Virginia, a man-made structure stands nearly 150 meters tall. This is the Green Bank radio telescope, a unique resource that is the largest fully steerable radio telescope in the world, with an antenna 100 meters in diameter. The radio telescope is at the heart of what was once called the National Radio Astronomy Observatory, and is now run by the Green Bank Observatory. The facility is in the middle of a radio-free zone, where cell phones go to die, since there is zero cell service in this region.
The facilities at this observatory are not just for the use of professional scientists. There is a 40′ radio telescope that is available for use by school groups to learn the principles of radio astronomy, and the principles of scientific observation. I was fortunate enough to chaperone two groups of high school seniors from South Charleston High School (SCHS) on their overnight excursions to this wonderful resource. The International Baccalaureate Physics teacher at SCHS, Janet Richardson, arranged for this field trip annually. I went in the years that my sons were in her physics class.
When we reached the observatory, we had a lecture from one of the observatory staff who explained what we were going to be looking for. The 40′ telescope is now fixed in place, so it allows observations of what is directly overhead as the earth rotates. This means that you can see the galaxy rotating towards you for one part of the day, and you can see the galaxy moving away from you 12 hours later. If you have a radio telescope tuned to the correct wavelength, you can observe the emissions from hydrogen gas found in our galaxy. If you remember the Doppler effect from physics, and you think about train whistles, you will remember that as the train is coming towards you, the pitch is higher. Then when the train passes you, the pitch lowers. That is the same phenomena that the radio telescope is observing. As the hydrogen gas in the galaxy moves towards you, the frequency moves up – the signal is shifted towards the blue end of the spectrum. If the gas is moving away, the signal shifts towards the red. By taking measurements around the clock, you can see the rotation of the galaxy as measured from our position on one of the outer arms of the galaxy.
The 40′ radio telescope is one of the first telescopes within the quiet zone of the observatory. Once you enter the quiet zone, there are no powered vehicles except for old diesels. Spark plugs are capable of creating intense interference for the radio telescopes, so you see Checker cabs from the 1940’s and 1950’s available to transport people. There are some diesel vans as well that are used to move the students back and forth. You enter the quiet zone after passing by the start of the scale model of the solar system, with the inner planets grouped closely together. Then a significant gap, and finally the symbol for Jupiter appears on the side of the road. The gaps between the planets grows, and we reach our destination for observation halfway between Uranus and Neptune. The building that accompanies the 40′ scope is small above ground. Once you enter the door, you descend a short flight of stairs to come to the observation room. This is a scientific instrument history display, but all of the analog dials and gauges and chart recorders are still working. I probably used similar chart recorders back in my college days in the 1970’s.
The room where the measurements are taken has been used by various school groups for decades. Mementos of these groups can be found scrawled on the ceiling beams, and the wall beams, where you can see which colleges, and which high schools left their mark for future students to see. The students have been instructed on how to tune the receiver to the correct frequency bandwidth, to start the chart recorder, and to begin their observational period. They move the frequency detector manually through that range, and the chart recorder shows the response. Hydrogen gas, if it is not moving relative to the observer, will emit radiation at 1420 mHz. If it is moving towards the observer, the frequency will increase, and if moving away, the frequency will decrease. As they step through the frequency range, all of a sudden the antenna picks up the signal from hydrogen, and the chart pen goes up. The height of the response is proportional to the concentration of hydrogen being observed. The students move the frequency through the entire assigned range, and the pen comes back down to the baseline. Thus completes one set of measurements. Each group of students makes two observations over the course of their stay.
The first year I went, Janet asked me to stay with the students through all of the late night observation shifts. So while each student only got to see one measurement in the middle of the night, I got to see multiple hours of observation, and really got the sense of seeing the motion of the galaxy in real time. But once the last group of students took their measurements, I was ready to go back to the bunkhouse where the boys in the group were sleeping. The accommodations are not spartan, but the dual rows of bunk beds do not allow for any privacy. They do enable a bit of mischief, like the spray cheese some of the boys put on the hand of another sleeping student, ensuring that when they tickled his face, he would smear the cheese all over his face. I, being a sound sleeper, heard none of this mild mischief.
On my second trip to the observatory, we saw the place where conspiracy theorists (the tinfoil hat crowd) would love. We got to go inside of a room-sized Faraday cage. A Faraday cage is an enclosure that does not permit electromagnetic radiation of certain frequencies to enter or leave. This is where the computer equipment is for the observatory. Since the antennas are so sensitive to stray radiation, the computers have to be totally shielded away from the antennas. The walls, ceiling, and floor are all impregnated with a copper mesh. There are holes in the mesh, because they are only concerned with blocking radiation of certain wavelengths and the size of the holes in the mesh govern the size of waves that can escape.
For this middle-aged self-admitted science and astronomy nerd, the two days off work that I took for these trips were some of the better vacation days I ever spent. It’s now been 10 years since my older son took his trip. I asked both my sons about what they remembered, but it seems that the details of the science portion has been lost to the vagaries of time. I asked Janet what she had the class do with their measurements once they returned to the classroom, and she said that their task was to get an image of the galaxy by looking at their observations over the course of a day. I cannot express my appreciation to teachers like Janet Richardson, who help to ignite the spark of curiosity in classes of young men and women. She said that in the future, they may get involved in the programs that they have to discover pulsars. It’s a crowd-sourced project, where the data from observations are available, and interested volunteers can use their computers and software from the observatory to try to detect pulsars that have not yet been identified.
I noted at the first of this post that the observatory used to be known as the National Radio Astronomy Observatory. It was funded by the National Science Foundation (NSF). As part of the ongoing disinvestment in science that began years ago, the NSF no longer provides 95% of the funds for the facility. Up until late in 2017, it was even feasible that the NSF would call for the demolition of the telescope. But since that time, a compromise was reached that enabled the observatory to stand as a self-sustaining organization. The Green Bank Observatory now is partnering with universities, like West Virginia University, and is involved with several multi-year projects including Project Breakthrough Listen, which is surveying the million closest stars to us and looking for signs of intelligent life. But like all such facilities, the needs for funds continues. If you would like to support the science programs of this unique facility that seeks to expand our knowledge of our origins, here’s the link to get involved: https://greenbankobservatory.org/engage/