Petra Mengistu '24 Wins Prestigious Chambliss Astronomy Achievement Student Award

Last month, at the 243rd meeting of the American Astronomical Society, Petra Mengistu ’24 was one of just 19 undergraduate students to receive the organization’s prestigious Chambliss Astronomy Achievement Student Award. She joined hundreds of her peers in New Orleans for the society’s annual poster competition, though, in our modern age, budding astronomers and astrophysicists have traded posterboards for high-definition screens for their presentations.

Mengistu, an international student who hails from Addis Ababa, Ethiopia, has had her eye on the heavens since fifth grade, despite some early hesitation when a teacher presented her with an assignment on black holes.

“I really don’t want to do this,” Mengistu, a physics and astronomy double major, recalls telling the teacher, who gently countered that she might actually like it. “And I absolutely did enjoy it. From then on, astronomy became a hobby for me.” That early engagement with exploring planets, stars, and the secrets of the cosmos led to work with the Ethiopian Space Science Society in high school, where she was involved in launching a CubeSat, a miniature four-inch satellite built from off-the-shelf electronic components.

At Haverford, Mengistu has been intensely focused on structures in galaxies known as bars and how they affect the overall life evolution of a galaxy, particularly their deaths. Her research was the crux of her award-winning presentation in New Orleans, titled “The Role of Galactic Bars on Star Formation,” and is the subject of her senior thesis. As their name implies, bars are rectangular-shaped features that can span almost the full size of a galaxy and draw materials inwards towards the center. They’re most often found in spiral galaxies like the Milky Way we call home, which is known to have a bar.

“In the classic picture of galaxy evolution, galaxies go from being young, active, and star-forming to getting older and inactive,” Mengistu says. Recently, as her thesis advisor Professor and Chair of Physics and Astronomy Karen Masters has observed, there’s a tendency to find them more often in older inactive galaxies, also known as quenching galaxies.

Consider bars a type of dynamic, galactic traffic jam showing where stars are situated in a galaxy, Masters says. Scientists believe the curious structures hold answers to how some galaxies live and die and carefully study their shape, strength, and speed at which they rotate through their galaxies, a measure called pattern speed.

They’re curious structures, Masters says, since spiral galaxies tend to be more active in star formation, but those with bars are much less active. “Is it because spiral galaxies that are less likely to form stars are forming bars, or is it because the bar is something that stops galaxies from forming stars?” Masters asks. “Petra is using some pretty complex data to investigate this question.”

“What we’re seeing is that strong and slow bars have the most pronounced impact on quenching in their host galaxies in ways that cause the galaxy to use up its gas within the barred region more quickly than it should,” Mengistu says of her research. “The galaxy dies faster, essentially, if it has a strong and slow bar at its center.”

To assist Mengistu’s search for answers, Masters connected her with colleagues in her research group, professors Rebecca Smethurst and Chris Lintott at Oxford University. Mengistu was also supported by their former PhD student, Tobias Géron, who, she says, helped lay the groundwork for her research. During the summer between her first and sophomore years, Mengistu led research on a separate, but still galactic, topic that was published as a research note. Later, with funding provided through the Marian E. Koshland Integrated Natural Sciences Center (KINSC), Mengistu spent last summer at Oxford immersed in her research.

Now, as Mengistu begins thinking about life post-Haverford, she’s waiting to hear from the 12 graduate schools she’s applied to. The Chambliss Award and her research, Masters says, will increase her chances of landing at one of her dream schools, especially as PhD programs have become more competitive and astrophysics remains a top pursuit.

“Our colleagues are telling us that if a student has had a chance to experience summer research as an undergraduate, they can see that they know what it means to do research and understand the rigors of a PhD program,” Masters says. “She’s really ready to go. Honestly, I’ve worked with PhD students, and Petra interacts with research like a PhD student already.”