Machine Learning and the Hunt for Earth Analogs Come to Carnegie’s Pasadena Campus – Pasadena Now
Scientists can find small planets by watching how their stars move back and forth. To do this, they must measure movements as small as 10 to 30 centimeters per second, or about 4 to 12 inches per second.
Lily Zhao, a NASA Sagan Fellow at the University of Chicago, will give a lunchtime talk in Pasadena about how astronomers are working to make these very precise measurements. According to the description published with Carnegie Science's event listing, she will explain how computer programs that learn from data have improved measurements of stars' movements toward or away from us. She will also discuss how these programs could shape future research.
Radial velocity is the part of a star's movement that is toward us or away from us. As a planet travels around a star, the planet's gravity pulls on the star, making it wobble back and forth. Tools such as MAROON-X, a spectrograph at the University of Chicago, can detect this wobble by measuring tiny changes in the color of the star's light, according to a University of Chicago news release.
In her talk description, Zhao wrote that scientists need measurements this precise to find planets with low masses, improve their understanding of how planets form, work out what planets contain inside, and improve models of their atmospheres. She wrote, "We are now in an era of unprecedentedly high-fidelity spectra."
On her research website, Zhao says she is the project scientist for EXPRES, a spectrograph on the 4.3-meter Lowell Discovery Telescope. She also says she founded the Extreme Stellar Signals Project, an international group working to tell the difference between signals caused by a star itself and signals caused by its planets. According to her website, signals produced by stars themselves are currently the biggest source of error in extremely precise radial velocity measurements.
In 2024, Zhao was one of 24 fellows chosen by NASA for its Hubble Fellowship Program. NASA selected them from more than 520 applicants, according to a NASA news release. The University of Chicago's astronomy department lists her proposed research project as "Enabling Radial Velocity Detection of Earth-Twins Through Data-Driven Algorithms and Community Collaboration."
According to the 2024 announcement, the Space Telescope Science Institute runs the program for NASA with help from the Chandra X-ray Center and the NASA Exoplanet Science Institute at Caltech/IPAC in Pasadena.
According to the Simons Foundation, Zhao earned her undergraduate degrees at the University of Chicago and her doctorate in astronomy at Yale University. She joined the Flatiron Institute's Center for Computational Astrophysics as a research fellow in 2021. While she was a graduate student at Yale, she was the lead author of a 2017 study that aimed to narrow the search for planets that might support life in the Alpha Centauri system, according to Yale News, the university's news office. Zhao described the study as "a very green study in that it recycles existing data to draw new conclusions."
In 2025, Zhao was one of the University of Chicago researchers who co-authored a study reporting four small planets orbiting Barnard's Star. Each planet has about 20 to 30% of Earth's mass, according to the university's news release about the study. The team studied observations collected by MAROON-X over 112 nights across three years.
Carnegie's Observatories began their history in December 1904. At that time, George Ellery Hale learned that Carnegie would provide money for the observatory he had proposed building on Mount Wilson, according to Carnegie Science. Hale had been looking for clearer skies than those near his hometown of Chicago.
NEED TO KNOW: The talk is called "Advancing Precision Spectroscopy and Detecting Earth Analogs" and is hosted by Carnegie Science's Observatories division. It will take place on Friday, October 23, from 12:15 p.m. to 1:15 p.m. at the William T. Golden Auditorium, Carnegie Observatories, 813 Santa Barbara Street. The event is listed as an in-person talk, and a Zoom link is also available. For more information, call Carnegie Science's main office in Washington, D.C., at (202) 387-6400, or visit carnegiescience.edu/events/