University of Chicago Students Discover One of the Oldest Stars in the Universe

The ancient star, named SDSSJ0715-7334, formed in a companion galaxy and migrated to the Milky Way billions of years ago.

Apr. 4, 2026 at 8:26am

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A highly structured abstract painting in earthy tones of brown, ochre, and deep blue, featuring sweeping geometric arcs, concentric circles, and precise botanical spirals, conceptually representing the ancient immigrant star SDSSJ0715-7334 and its journey through the cosmos.An abstract visualization of the ancient immigrant star SDSSJ0715-7334, which formed in a companion galaxy and migrated to the Milky Way billions of years ago, providing a rare glimpse into the early universe.Chicago Today

A class of undergraduate students at the University of Chicago has used data from the Sloan Digital Sky Survey (SDSS) to discover one of the oldest stars in the universe. The star, named SDSSJ0715-7334, formed in the Large Magellanic Cloud and migrated to the Milky Way billions of years ago. Analysis shows it has an extremely low metallicity, making it one of the most pristine stars ever observed.

Why it matters

This ancient immigrant star provides an unprecedented look at conditions in the early universe, as stars with such low metallicity must have formed from gas before most supernovae occurred. The discovery highlights how big data projects like SDSS are enabling students to make important contributions to astronomy.

The details

The ten students found the star as part of their "Field Course in Astrophysics" at the University of Chicago, led by Professor Alex Ji. After examining thousands of stars from SDSS data, the students observed the star for three hours at the Las Campanas Observatory in Chile. They found the star has the lowest metallicity of any star yet observed, with only 0.005% of the metals found in our Sun. This suggests the star formed from some of the earliest gas in the universe, before most supernovae had occurred.

  • The students discovered the star on March 21, 2025 during their Spring Break trip to the Las Campanas Observatory.
  • SDSS, the international collaboration that operates the survey the students used, has been running for 25 years.

The players

Alex Ji

Professor at the University of Chicago and the deputy Project Scientist for SDSS-V.

Natalie Orrantia

One of the students who made the discovery of the ancient immigrant star.

Ha Do

One of the students who made the discovery of the ancient immigrant star.

Juna Kollmeier

The Director of SDSS-V.

SDSS

The Sloan Digital Sky Survey, an international collaboration of over 75 scientific institutions that has been operating for 25 years.

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What they’re saying

“We found it the first night, and it completely changed our plans for the course.”

— Alex Ji, Professor, University of Chicago

“I was looking at that camera the whole night to make sure it was working.”

— Natalie Orrantia, Student, University of Chicago

“This ancient immigrant gives us an unprecedented look at conditions in the early universe.”

— Alex Ji, Professor, University of Chicago

“To be able to actually contribute to something like this, it's very exciting.”

— Ha Do, Student, University of Chicago

“These students have discovered more than just the most pristine star. They have discovered their inalienable right to physics.”

— Juna Kollmeier, Director, SDSS-V

What’s next

The team plans to continue analyzing the star to learn more about the early universe, and the students involved are considering pursuing graduate careers in astronomy.

The takeaway

This discovery highlights how big data projects like SDSS are empowering students to make groundbreaking contributions to our understanding of the cosmos, even at the undergraduate level.