This is an article from the spring 2020 issue of LSA Magazine. Read more stories from the magazine.
An ambitious and dedicated student with a love of science, Tali Khain (B.S. ’19) emailed Arthur F. Thurnau Professor of Physics David Gerdes right after high school graduation to ask if he had any research projects she could work on the summer before she became a student at U-M.
Surprisingly, Gerdes did.
“I didn’t really have formed interests,” Khain says. “I just vaguely knew I liked math and physics, and everyone in the research group was lovely.”
The group Khain joined was led by Gerdes and Ta-You Wu Collegiate Professor of Physics Fred Adams. The team’s research focused on analyzing the outer solar system using data gathered from the Dark Energy Survey (DES), an international collaboration of more than 400 scientists from more than 25 institutions who are exploring the universe’s origins by mapping galaxies far beyond the Milky Way.
As Khain’s interests and knowledge developed, she was given more freedom to pursue the aspects of the project she found most interesting. For Khain, the project felt like a dream come true.
“I got really lucky,” Khain says. “To be quite honest, everything sort of feels like an accident.”
Everything in Motion at Once
Beyond Neptune, thousands of (relatively) small balls of ice and rock orbit the sun, the dust and debris left behind after the solar system’s formation that never coalesced into something larger, like a planet. These are Kuiper (rhymes with “hyper”) Belt objects, or KBOs. “I call them cosmic leftovers,” says Gerdes. “The same processes that gave birth to the Kuiper Belt gave birth to Earth and to us. When we study the outer solar system, we’re writing chapters in the story of where we came from.”
Using powerful telescopes, the DES has captured images of distant solar systems roughly the equivalent of detecting a single candle halfway to the moon. Using this data, the research group identified hundreds of KBOs, some as small as 100 km in diameter.
KBOs have elliptical orbits: some long and skinny, some inclined, some unstable, some very long and very skinny. Because everything in the solar system is in motion at once, calculating orbits on paper is tricky, so theorists rely on computational simulations to analyze the images and run experiments. Using this method, Khain created a scheme to classify the dynamics and specific trajectories of some 300 objects, and then used that method to actually code all of their properties.
The simulations track the orbits of the planets and objects over time. Khain calculated and analyzed how the orbits of specific KBOs have, or haven’t, changed. Because KBOs take hundreds, or even thousands, of years to orbit the sun, Khain’s work allows the research team to predict the behavior of these objects over millions of years of their orbital evolution.
Though it can be arduous, the work of combing through complicated data sets excites Khain.
“By using physics, math, and modeling, we can understand if there’s a driving mechanism that explains the complexity of the solar system,” says Khain. “We want to find the simplest explanation for what’s going on. It’s really exciting when you don’t quite know what you’re looking for and then you find a pattern.”
A New Frontier in Our Cosmic Backyard
During a summer research assistantship at the California Institute of Technology (Caltech), Khain used computational modeling to analyze the orbits of several KBOs whose particularly weird orbits all bizarrely point in the same direction.
One possible explanation for the coordination? A massive, undiscovered planet, hypothetically called Planet Nine.
If Planet Nine exists, its orbit is probably elliptical and unlike the circular orbits of other planets. It’s also very big, much bigger than any KBO.
At Caltech, Khain worked with professors Konstantin Batygin and Mike Brown, experts in Planet Nine, as first author on a paper that investigates the relationship between KBOs and Planet Nine using numerical simulations. “It would be amazing if Planet Nine were found," Khain says, "in part because there is very indirect evidence of its existence.”
Before she graduated, Khain’s involvement with these research projects conferred an expertise in the dynamics of planetary systems, and the numbers speak for themselves. She made original contributions to ten peer-reviewed publications, including three as the first author, and has one additional first-author paper currently under review. She presented on the dynamics of the outer solar system at research conferences, where she was often mistaken for a graduate student or postdoctoral fellow. In 2019, Khain received the American Physical Society LeRoy Apker Award in undergraduate physics achievement, which honors phenomenal achievements in undergraduate physics research.
Now a graduate student at the University of Chicago, Khain studies soft matter, another classical physics field that examines how systems of particles interact in various ways. It’s similar to her work with the outer solar system but on a much smaller scale.
Khain’s scientific accomplishments are well beyond her years, and she says that doing research as an undergraduate enabled her to approach her work from a place of wonder and play.
“It’s nice when you’re an undergrad because you don’t have high stakes,” Khain says. “Planet Nine is such an interesting problem, the orbit is so weird. I found the physics of it very fun.”
The research groups she worked with inspired Khain to explore open-ended problems and added dimensions of meaning and joy to her undergraduate education. Ultimately, she says, it was this collaboration that launched her success.
“The value of a mentor can’t be overstated,” says Khain. “Research is difficult, and it’s important to have people who encourage you to go on. It’s a gift.”
