Alum Finds Exoplanets at Yale

The stars and the way Earth fits into the universe’s bigger picture intrigue many people. It’s pretty rare, though, for someone to be on the cutting edge of finding the planets that fill out that picture.

That’s exactly what Sarah Millholland ’15 started at St. Thomas and now continues at Yale University. She recently contributed to the discovery of some 60 new exoplanets; known as hot Jupiters, these bizarre planets have temperatures that can reach above 2,000 degrees and orbit around stars found far outside our solar system.

“It’s really exciting,” Millholland said. “This project in particular was introducing a new method of finding exoplanets: We were looking at reflected light from the star. People have been proposing that for seven years or so, but no one had undertaken it. It’s cool to be at the forefront of this development.”

Using images from the NASA’s Kepler telescope to base their searching, Millholland’s work helps put our planet into perspective.

“It’s about understanding how our planet and solar system fit in with respect to all these other systems,” she said. “The diversity of planets in the universe and the question, ‘Is this [Earth] a common one, or are we on a rare planet?’ It’s really about our cosmic context.”

Looking upward

Millholland discovered and grew her passion for the stars while she was at St. Thomas, where she originally started as a math student. Some serendipitous scheduling put her in associate professor Gerry Ruch’s introductory physics course her freshman year; she quickly proved exceptionally adept.

“We have six exams. A perfect score on one of those is pretty rare; you’ll maybe see one in the stack. It’s unheard of for someone to get 100 percent on all six, which Sarah did. She aced everything. And everything in the next physics class. She just tore it up,” Ruch said.

Ruch pulled Millholland into a summer research project after her freshman year modeling planets’ rotations around their respective stars. Millholland quickly moved past anything Ruch originally had in mind for the scope of her work, learning from scratch how to code software and eventually developing the programming needed for St. Thomas’ south campus observatory to observe exoplanets. Throughout her four years at St. Thomas she also published papers, presented at a national astronomy conference and secured the prestigious Goldwater Scholarship.

“She’s one-student-in-20-years smart. Ridiculously smart,” Ruch said. “As a freshman coming in she didn’t realize it, so my job was to point her in a direction.”

Millholland said the tutelage of Ruch and the physics faculty was the key to everything she did at St. Thomas.

“I can’t even express in words how instrumental it was to have the physics faculty be so supportive of my academic and research development,” she said. “That’s a huge strength of St. Thomas: You formulate closer relationships with your advisers. Larger universities are more focused on their grad students. Right from the beginning I thought it was so cool you could teach in the classroom and also explore what you’re passionate about in your research. The passion professors there bring to both sides is amazing.”

All her research and coding experience at St. Thomas also gave Millholland a leg up in graduate school at University of California, Santa Cruz, where she connected with adviser Greg Laughlin. When Laughlin went to Yale in 2016 he asked Millholland to join him, and their continued work there is a testament to collaboration and the joy of discovery.

“I would put [finding a new exoplanet] analogous to a sports moment, where you’re just very, very excited. I’ll run up to [Laughlin] like, ‘Look at this!’” Millholland said. “I have to credit him for being very, very excited, which has kept me very excited about these new developments. It’s definitely super fun to work on.”

Millholland said her work over the next three years for her Ph.D. will likely focus on more theoretical areas than the exoplanet hunting she’s undertaken so far, but her overall goal is tied directly back to the teaching emphasis of her St. Thomas professors.

“I’m pretty passionate about teaching students about exoplanets, so a research and teaching path is what most interests me,” she said.