A view of snow-capped Mount Graham. Credit: Larry Lebofsky

What is citizen science? The CosmoQuest website has this definition: “Put simply, citizen science is any science done by everyday people that has the potential to lead to new understanding of the universe we share. This can vary from people studying Earth’s climate change by recording when the first flowers bloom, to studying weather on Mars by recording the seasonal dust storms.” This is a very broad definition. At one extreme, a citizen scientist can be someone whose computer runs SETI@home which uses their computer to analyze radio telescope signals to search for alien signals. At the other extreme, a citizen scientist can be an amateur astronomer who has a 30-inch telescope, a sophisticated imaging system, and has orbital analysis programs that can calculate the orbits of near-Earth asteroids (NEOs) that might someday collide with the Earth.

Even though I spent most of my career as a professional planetary astronomer, something I now do several times a year as a “hobby” is to use a large telescope to look for NEOs; more of this later. This, then, makes me and my co-observers citizen scientists.

Back in early June I wrote an article about Hunting for Saffordites. At that time, I showed a picture of snow-capped Mt. Graham, west of where we were hunting in January and February.

Submillimeter Telescope (10-meter diameter mirror) in foreground with Large Binocular Telescope in background at sunset: Credit Larry Lebofsky.

Mt. Graham is located about 125 miles east and a little north of Tucson, AZ, where I live. Mt. Graham is home to the Mount Graham International Observatory’s (MGIO) three telescopes as well as the endangered Mt. Graham red squirrel. The three telescopes on Mt. Graham include the Heinrich Hertz Submillimeter Telescope (SMT), the Large Binocular Telescope (LBT), and the Vatican Advance Technology Telescope (VATT). Yes, the Vatican has a telescope in Arizona at an altitude of 10,425 ft, just under 2 miles up! The VATT has a 1.8-meter diameter mirror which was the first mirror spun and polished at the University of Arizona’s Mirror Lab. For the professional astronomical community who has access to telescopes with mirrors 3 or more meters in diameter all over the world, this is not a large telescope. But to the amateur with his backyard telescope, this is a large telescope.

Large Binocular Telescope (2 8.4-meter diameter mirrors). Credit: Larry Lebofsky.

The goal of our program is to recover virtual impactors and important, potentially hazardous asteroids. A virtual impactor (VI) is an asteroid that, with orbital uncertainties, could impact the Earth sometime in the near-future. A potentially hazardous asteroid (PHA) is an asteroid that, with orbital uncertainties, could come within 0.05 AU of the Earth (an AU is the mean distance of the Earth from the Sun; 0.05 AU is about 20 times the distance of the Moon from the Earth). “Recover” means observing asteroids that have been observed for a short period after their discoveries and have not been observed in about a year or more. There is a more technical definition of “recovery,” but this one works for most objects. These asteroids might become “lost” because of the uncertainty in their orbits. Our second priority is orbital extensions, making observations of asteroids that might have not been observed in a few months but are still observable with a telescope as large as we are using. Again, these asteroids have the potential to get lost and never be observed again, unless rediscovered accidentally with one of several NEO surveys. By reducing the uncertainty in the orbits of these asteroids, we hope to remove them from the list of VIs and PHAs.

A view of the VATT. This is our “home” for the duration of our time on the telescope. Credit: Larry Lebofsky.

I am part of a team that is fortunate enough to be able to propose for and get time on the VATT. We are now going up there two or three times a year for observing runs that last two or three nights. The team includes me, Mark Trueblood, and Robert Crawford. I am a retired planetary scientist from the University of Arizona and now work part time doing education outreach with Girl Scout adult leaders through the University of Arizona and teacher professional development at the Planetary Science Institute. Mark is a retired project manager who is the Director of the Winer Observatory in Sonoita, AZ. Robert is the owner of Rincon Ranch Consulting which specializes in air pollution control. Since none of us is paid for our observing at the VATT, we are citizen scientists!
From the MGIO basecamp, it is about 28 miles to the observatory, with the last two miles on a one-lane access road. You know that you are approaching an astronomical observatory because there are markers (for emergencies) at the access roads’ switchbacks that are named for the brightest stars in the Pleiades.

A view of the Mt. Graham access road with the sign labeled Electra, one of the stars in the Pleiades. The view in the distance shows some of the devastation left by the 2004 Nuttall Fire. Credit: Larry Lebofsky.

Each night there is a detailed startup procedure which includes putting liquid nitrogen in the Dewar (a thermos-bottle-like container for the imager) and turning on all of the equipment for running the telescope and the imaging camera. For our group, Mark runs the telescope, Larry runs the camera, and Robert analyzes the images, looking for our target asteroids. Mark is responsible for most of the telescope startup at the beginning of the night and then is responsible for moving the telescope to the field where we hope to find the asteroid.

The 1-8-meter telescope. Credit: Larry Lebofsky.

Larry takes the images, makes sure that the data files are labeled correctly, and are put into the proper directories for analysis. He also keeps a record of the observations (weather conditions, object being observed, time of observation, integration time, focus settings, etc.) in a logbook that can be referred to on future nights and observing runs. Robert downloads the images and analyzes them, looking for the moving object that we hope is our target asteroid. Once we have observed the object at least three times, which gives us the motion of the object as well as its brightness, he then sends our observations to the Minor Planet Center where identity of the object is verified and the results are posted for other observers to see.

Filling the Dewar. As the liquid nitrogen goes into the Dewar, it cools the metal tubing used to transfer the nitrogen into the Dewar reservoir. The first liquid that is seen is actually liquid oxygen condensing on the outside of the transfer tube. Credit: Larry Lebofsky.

The primary target for our observing run in November (Thanksgiving) was 2015 XF261, an asteroid that was discovered in late 2015 and had not been observed in nearly a year. This asteroid is estimated to be about 50 meters in diameter, twice the diameter of the Chelyabinsk asteroid. 2015 XF261 is an Aten asteroid whose mean distance from the Sun is less than that of the Earth, but whose farthest distance from the Sun is outside Earth’s orbit. Given the uncertainty in its orbit, there was a small chance that it would hit the Earth in 2106. With our observations and some taken a few days later by another group, the orbit is now known well enough so that there is no chance in the foreseeable future that 2015 XF261 will hit the Earth. However, in 2090, it is now predicted to pass between the Earth and the Moon.

On this two-night observing run we observed and submitted for publication this and one other faint near-Earth asteroid. Unfortunately, we lost parts of both nights due to poor weather conditions. But we did get our primary object and removed it from the list of virtual impactors!

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Mark and I went back to the VATT three weeks later for another two-night run. This was only a few days after full Moon, limiting our ability to do faint asteroids, but we were offered the time and could not turn down the opportunity to observe additional objects. Robert was not able to come, so Dave Bell, a software manager at the National Optical Astronomy Observatory was able to join us. Despite snow the first night and clouds for some of the second night, we were able to observe and submit for publication three objects. Again, our observations and subsequent observations by others have removed these asteroids as potential threats to the Earth!

Three images of asteroid 2016 XA2. We track on the moving asteroid so the star images are elongated. With three separate exposures we can see the motion of the asteroid relative to the “fixed” stars. Credit: Dave Bell and Larry Lebofsky.

Over 90% of the NEO discoveries are made by a few groups that are supported by NASA. However, most of the follow-up observations are done by amateur astronomers, citizen scientists who dedicate their evenings and nights to providing the observations that help scientists to determine the orbits of these asteroids, assuring that they will not become “lost” due to poorly known orbits. We are fortunate enough to be able to have access to large telescopes, by amateur standards, and so can observe asteroids that are fainter than what can be attained by amateurs with smaller telescopes.