Undergraduate Astronomers Observe Rare Asteroid Eclipse
Students Co-author Paper After Analyzing Celestial ‘Fossils’ That Hint at Solar System’s Birth
An artist’s concept of the Jupiter Trojan asteroids, mysterious space rocks that orbit around Jupiter in its path around the sun.
Image courtesy of NASA/JPL-Caltech
When images of a distant asteroid called 617 Patroclus grew dim across Oliver O’Brien’s computer screen, they knew that they were witnessing something rare.
“We were observing what’s called ‘mutual events’ between Patroclus and another similarly sized asteroid in its orbit called Menoetius,” said O’Brien ’26, a University of Maryland astronomy and anthropology dual-degree student. “These two asteroids circle each other every 103 hours, but once in a while, they pass in front of each other or shadow each other from our perspective. We knew we only had one chance at capturing these mutual events within our time constraints.”
This wasn’t just part of an assignment for the “Special Problems in Astronomy” course on stellar and high-energy astrophysics with Astronomy Principal Lecturer Melissa Hayes-Gehrke—O’Brien and their classmates were collecting and analyzing data that could influence the flight plan of a billion-dollar NASA mission.
O’Brien is now the second author of a paper published this month in The Minor Planet Bulletin detailing the observations. The team also included astronomy majors Natalie Haugen ’26, Jorge Argueta ’25, Sarah Blaufuss ’25, Bodie Breza ’25 Joseph Kleinman ’26 and Nardos Mekonnen ’25; and astronomy and physics double majors Isabella Sanford ’25 and Qinyan Lu ’26. Their goal was to use the data collected from their observations of the asteroids Patroclus and Menoetius to help NASA researchers gain a better idea of what its Lucy spacecraft would encounter at the Jupiter Trojan asteroid belt during its planned flyby in 2033.
NASA’s Lucy spacecraft, launched in 2021, will pass by Patroclus as it makes its journey through Jupiter’s Trojan asteroid belt years from now. Mission planners need detailed information—such as the asteroids’ sizes, shapes and orbital patterns—before its arrival to map a safer, more efficient flight plan. Remotely using telescopes at Australia’s Siding Spring Observatory, O’Brien studied the asteroids’ changing brightness as they eclipsed and occluded each other and compared the light curves with predictions that the team already made to better understand Patroclus and its surroundings.
“There were a few discrepancies between the brightness and timing of the event, which is exciting because that means there’s something new to discover, more theories to explore,” O’Brien said. “We believe that there’s probably an unknown variable within Patroclus’ and Menoetius’ system that’s contributing to that difference, maybe more complex asteroid shapes or orbit irregularities that we haven’t accounted for.”
The observing nights came with significant challenges. Technical glitches and focusing malfunctions left many images looking like “huge doughnut shapes instead of small points of light,” according to Hayes-Gehrke, first author of the paper and O’Brien’s adviser on the project.
However, rather than give up, O’Brien took the lead.
“Oliver worked painstakingly to get all the work done properly,” Hayes-Gehrke said. “They patiently redid the analysis several times with many alterations to improve the outcome. And the finished results were amazing.”
For O’Brien, spending hours addressing the glitches and errors was more than just a school project—O’Brien believes the team’s findings helped to reveal patterns in the sky that tell a story billions of years in the making.
“The main driving force behind our work and NASA’s Lucy mission is to study the building blocks of the solar system,” O’Brien explained. “Patroclus was one of the asteroids selected because it can showcase what the solar system was like when it was first forming.”
O’Brien’s fascination with origins also led them last summer to trade telescopes for trowels during an archaeological dig in Ireland. In the home country of many of O’Brien’s ancestors, they unearthed human artifacts that hinted about the culture of people who lived there long ago.
Both the published astronomy paper and the dig in Ireland “were eye-opening parts of my time here at UMD, especially because my paper on Patroclus was my first formal research experience.” O’Brien said. “We weren’t just going through the motions for a class; we were collecting data to be uploaded to the Asteroid Lightcurve Photometry Database for other researchers to use.”
As NASA’s Lucy spacecraft speeds closer to the Trojans, O’Brien hopes that their work will lay the groundwork for other astronomers and researchers to study the universe’s evolutionary story. By tracking the movements and features of faraway asteroids, O’Brien hopes to help piece together the history of the solar system and potentially the origins of life itself.
“I want to understand where we came from, how we got to be what we are today, and where else life might exist,” they said. “The answer probably goes beyond what we can find on Earth.”
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