Undergraduate Students Discover "Ancient Immigrant" Star from the Early Universe Drifting Through the Milky Way

Undergraduates discover an "ancient immigrant" star with record-low metallicity. Learn how SDSSJ0715-7334 traveled from another galaxy to our own.

By: AXL Media

Published: Apr 4, 2026, 9:38 AM EDT

Source: Information for this report was sourced from the Sloan Digital Sky Survey (SDSS).

A Discovery Born from Undergraduate Research

What began as a routine academic exercise in a University of Chicago astrophysics course has resulted in a landmark astronomical discovery. Ten undergraduate students, working under the guidance of Professor Alex Ji and a team of graduate assistants, utilized the vast datasets of the Sloan Digital Sky Survey (SDSS) to hunt for rare stellar candidates. After sifting through thousands of stars, the group identified a "pristine" candidate that appeared to belong to the universe's earliest generations of suns. The discovery highlights the growing power of big data in allowing students to contribute to high-level scientific breakthroughs.

The "Ancient Immigrant" Across Galactic Boundaries

Further analysis revealed that the star, designated SDSSJ0715-7334, is not a native of the Milky Way. By combining their spectral observations with positional data from the European Space Agency’s Gaia mission, the team traced the star’s trajectory back billions of years. They determined that it was born in the Large Magellanic Cloud (LMC)—the Milky Way's largest satellite galaxy—and was eventually pulled into our galaxy by gravitational forces. Because of its extragalactic origins and extreme age, Professor Ji dubbed the find an "ancient immigrant," providing a unique opportunity to study the early chemical evolution of a galaxy other than our own.

Record-Breaking Purity and Cosmic Origins

In astronomy, "metals" refers to any element heavier than hydrogen and helium. SDSSJ0715-7334 has the lowest metallicity ever recorded for a star, containing less than half the heavy elements of the previous record-holder. Specifically, it possesses only 0.005% of the metallic content found in our Sun. Because these heavier elements are created and dispersed through supernova explosions over time, a star with such extreme purity must have formed before the universe was "polluted" by multiple generations of dying stars. This suggests SDSSJ0715-7334 is a "time capsule" from a period shortly after the Big Bang.