Student Team Finds One of the Oldest Stars in the Universe that Migrated to the Milky Way
#Population III star#Sloan Digital Sky Survey#stellar migration#Large Magellanic Cloud#metallicity#University of Chicago#ancient star#astrophysics education
📌 Key Takeaways
Undergraduate students discovered an ancient, metal-poor star within the Milky Way using SDSS data.
The star's composition indicates it formed in the early universe, making it a rare Population III candidate.
Orbital analysis shows the star originated in the Large Magellanic Cloud and migrated to our galaxy.
The find demonstrates the educational and scientific value of integrating real survey data into university curricula.
📖 Full Retelling
A team of ten undergraduate students from the University of Chicago, led by Professor Alex Ji, discovered one of the oldest known stars in the universe, named SDSS J0715-7334, on March 21, 2025, using data from the Sloan Digital Sky Survey (SDSS) and follow-up observations from the Las Campanas Observatory in Chile. The star, located 79,256 light-years away within our Milky Way galaxy, is significant because its extremely low metal content indicates it formed in the universe's infancy, and orbital analysis reveals it migrated from the Large Magellanic Cloud, a satellite galaxy, billions of years ago.
The discovery was made as part of a hands-on astrophysics field course where students sifted through vast SDSS datasets. After identifying thousands of candidates, they used the Magellan telescopes to observe 77 promising stars, ultimately focusing on SDSS J0715-7334 for three hours. Spectral analysis showed the star is composed almost entirely of hydrogen and helium, with a metallicity—a measure of elements heavier than helium—of just 0.005% that of our Sun. This makes it a pristine Population III star candidate, a type theorized to have formed from primordial gas before supernovae seeded the cosmos with heavier elements.
Further investigation, incorporating data from the European Space Agency's Gaia mission, traced the star's motion back to the Large Magellanic Cloud. This migration history, coupled with an undetectable level of carbon in its spectrum, suggests a unique formation pathway involving an early "sprinkling of cosmic dust." Professor Ji noted the find, nicknamed the "Ancient Immigrant," upended the course's plans and provides an unprecedented window into early cosmic conditions. The discovery underscores how large-scale astronomical surveys are democratizing science, enabling student-led breakthroughs that challenge our understanding of stellar evolution and galactic history.
The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (163,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (c. 16 kiloparsecs (52,000 light-years) away...
Multi-spectral imaging and spectroscopic redshift survey
The Sloan Digital Sky Survey (SDSS) is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 and was named after the Alfred P. Sloan Foundation, which c...
In 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations.
In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926.
Baade observed that bluer stars were strongly associated with the spiral arm...
The University of Chicago (UChicago, Chicago, UChi, or U of C) is a private research university in the Hyde Park community area of Chicago, Illinois, United States.
The university is composed of an undergraduate college and four graduate research divisions: the Arts & Humanities Division, the Biolog...
Student Team Finds One of the Oldest Stars in the Universe that Migrated to the Milky Way By Matthew Williams - April 10, 2026 10:28 PM UTC | Extragalactic Ten undergraduate students from the University of Chicago made an astounding discovery using data from the Sloan Digital Sky Survey . As part of their "Field Course in Astrophysics," they located one of the oldest stars in the Universe living in the Milky Way. The star, SDSS J0715-7334 , is a red giant with 29 times as much mass as our Sun, located 79,256 light-years away. But here's where things truly get interesting: according to their findings, this star wasn't born in the Milky Way, but migrated here from another galaxy. The team is led by Professor Alex Ji , the deputy Project Scientist for SDSS-V, and graduate teaching assistants Hillary Andales and Pierre Thibodeaux. The SDSS-V program began in 2020 and is the latest phase of the Survey's 25-year commitment to acquiring spectra of millions of objects in the Milky Way and beyond, to improve our understanding of how stars, black holes, and galaxies grow and evolve. The program relies on two telescopes in both hemispheres to provide full-sky coverage, including the 2.5-meter Sloan Foundation Telescope at Apache Point Observatory in New Mexico and the 100-inch du Pont Telescope at Las Campanas Observatory in Chile. In Ji's class, the SDSS is embedded into the class curriculum, and the student team spent the first several weeks looking through its data for interesting stars. After examining several thousand candidates, they flagged 77 for follow-up observations using the Magellan Inamori Kyocera Echelle instrument on the Magellan telescopes at the Las Campanas Observatory. On the evening of March 21st, 2025, they found SDSS J0715-7334 and observed it for three hours. *The Large Magellanic Cloud, a satellite galaxy of the Milky Way, as imaged from the Hubble Space Telescope. Credit: NASA/JPL-Caltech* From its composition, almost entirely hydrogen/helium, they de...
