Atop a Chilean mountain, undergraduate students make cutting-edge astronomical observations

Editor’s Note: This is part of a series called UChicago Class Visits, spotlighting transformative classroom experiences and unique learning opportunities offered at UChicago.

At the top of a mountain in the Chilean Andes, peering into the cosmos from 8,000 feet above sea level, a University of Chicago student had a revelation.

“I sat down at the telescope on our first night on the mountain and started taking observations, and I realized immediately it was what I wanted to do with the rest of my life,” said Sarah Grannis, a third-year undergraduate student. “It was nothing short of career-defining for me.”

Grannis was part of a field course in astronomy and astrophysics at UChicago, which immerses students in the full scientific process: how to propose and design an astronomical experiment, how to make observations at a telescope, and how to analyze the data and publish it. Students and alumni of the class have already published six papers in scientific journals.

Previously, due to pandemic travel restrictions, the class had to conduct observations remotely. But this past spring break, seven students were able to travel to the Magellan telescopes at Carnegie Science's Las Campanas Observatory in Chile to use the telescopes for research.

“It was amazing, I don’t know how to describe it,” said third-year student Joseph Yeung. “It’s crazy to be in the driver’s seat, sitting there in the moment and knowing you’re one of the first people—maybe the first person ever—to see this light.”

Universal mysteries

Prof. Mike Gladders has taught the course since its inception in 2020. In his mind, the course is an opportunity to not only teach students about astronomy, but for them to make new contributions to the scientific literature while doing so.

In the first quarter of the course, the students learn about astrophysics as well as the telescopes and the types of measurements and calibrations that can be made. Then they search existing databases of the sky to try to find promising objects to look at more closely with the Magellan telescopes.

In particular, they are searching for extremely distant galaxies that have been “lensed”—magnified like a fish through the fishbowl, thanks to the enormous power of gravity. The light from these far-away galaxies has been traversing the cosmos at the speed of light for billions of years, and so the students were looking back in time to the deep past, when both the universe, and the galaxies in it, were young. These galaxies are of interest to scientists because they provide clues about the physical processes that helped form and shape galaxies over cosmic time.

In the early days of the cosmos, the universe mostly consisted of dark clouds of hydrogen gas. Then, about 500 million years after the Big Bang, some intense form of radiation began ionizing the hydrogen, leading to the makeup of the universe that we know and love today. “This launches the development of complexity in the cosmos,” said Gladders. But very little is known about how this happened; finding these very early galaxies can offer clues to the processes at work.

Once the students have identified promising objects to take a closer look at with the telescopes, they travel to Chile over spring break to make those observations.

‘A mad scramble’

The excursion is possible, in part, because the University of Chicago is a partner of the Magellan telescopes at Carnegie Science's Las Campanas Observatory and has institutional access to the telescopes.

Because it was over spring break, the trip was short and intense. To get to the telescopes, the group flew to Santiago, Chile, then took a smaller plane to a town called La Serena, and then drove for several hours into the mountains before staying up to make observations at night.

At 8,000 feet, the air is significantly thinner than in Chicago, which makes it great for observing the sky but taxing for humans used to the plentiful oxygen at sea level. “The first night was a mad scramble,” said Gladders. “By the second night we had our feet a little more underneath us.”

The students took observations at the telescopes in shifts throughout the night.

“Until that point, I had only had experience analyzing data that had already been taken and processed for me,” said third-year student Camila Silva. “But when you are taking the data yourself, you gain a really good sense of how every single adjustment, calibration, and decision you make during observing will affect the validity and quality of the data you get.

“Getting to have that firsthand experience really instilled a deep reverence for the scientific process in me,” she said.

In between shifts, the students could step out and see the night sky with the naked eye, which was also intense; the mountain was chosen because it is one of the darkest and clearest skies on Earth. “The stars are like nothing you’ve ever seen in your life,” said Grannis.

They also took side trips to visit other observatories in the area, including the Gemini and Blanco telescopes and the construction site for the upcoming Vera C. Rubin Observatory, which will serve as a flagship ground telescope; as well as visiting a nearby cloud forest in the mountains that is so unique it is designated as a UNESCO biosphere reserve.

A meaningful experience

Back in Chicago, the students are now analyzing the data they took and preparing for eventual publication.

As members of the course, the students join an ongoing collaboration known as COOL-LAMPS (for ChicagO Optically-selected strong Lenses – Located At the Margins of Public Surveys). Consisting of current and former members of the course as well as collaborators from multiple other institutions, the collaboration has published multiple studies in scientific journals and is preparing more.

“It really struck me when Professor Gladders said at the beginning of our first class that our collaboration is actually one of the leaders in this particular field of science,” said Yeung. “Since the class started a few years back, we’ve been leading the observations and data analysis of these types of astronomical objects. It makes me feel like I’m not just a student; I’m also an astronomer.”

For his part, Gladders is thrilled to be able to fully realize his original vision for the course by traveling to the telescope.

“I do what I do because 25 years ago, I got the experience to work at a significant research telescope—and that feeling is why I’m here now as a professor,” he said. “To stand under the sky like that, to appreciate it as a curious being looking out into the cosmos, is something you just have to experience. And to couple that with being able to ask and even answer certain questions about what you’re looking at—together, those are very powerful.

“People do transformative things when they are inspired by transformative experiences.”