A classroom search led to a remarkable stellar find

A group of undergraduate students at the University of Chicago has identified what may be one of the oldest known stars in the universe, and the object appears to have an origin story even more unusual than its age. According to Universe Today, the star, designated SDSS J0715-7334, is now in the Milky Way but likely formed in another galaxy before migrating here.

The discovery grew out of a “Field Course in Astrophysics” led by Professor Alex Ji, with graduate teaching assistants Hillary Andales and Pierre Thibodeaux. Working with data from the Sloan Digital Sky Survey, students spent weeks examining thousands of stellar candidates and narrowed them to 77 objects for follow-up observations. On March 21, 2025, they observed SDSS J0715-7334 for three hours using the MIKE instrument on the Magellan telescopes at Las Campanas Observatory.

Why this star stands out

Universe Today reports that SDSS J0715-7334 is a red giant located 79,256 light-years away and has an extraordinarily low metallicity. Its composition is described as almost entirely hydrogen and helium, with only 0.005% of the metals found in stars like the Sun. The report says this gives it the lowest metallicity of any star yet observed.

That is the key to its significance. In astronomy, “metals” means elements heavier than helium. The earliest stars formed before the universe had been significantly enriched with those heavier elements. Later stellar generations inherited progressively more of them after earlier stars lived, exploded, and seeded space with new material. A star with extremely little metal content is therefore a clue to a much earlier cosmic era.

In that sense, SDSS J0715-7334 is valuable not only as an object in the sky but as a record of conditions close to the beginning of stellar history. It appears to belong to a population that formed after the very first stars had already ended their lives and enriched the universe just enough for a second generation to emerge.

The migration story may be just as important

The most striking twist is that the star may not be native to the Milky Way at all. Universe Today says the team concluded that it migrated from another galaxy. That claim adds a galactic archaeology dimension to the discovery. The Milky Way is not a static, closed system; it has grown over time by interacting with and absorbing smaller companions. A star like this could therefore act as evidence of that long history of assembly.

The report specifically references the Large Magellanic Cloud, one of the Milky Way’s satellite galaxies. While the supplied text does not fully detail the chain of evidence connecting the star to a specific origin, the core point is clear: researchers believe this ancient object formed outside our galaxy and later became part of it.

If that interpretation is correct, the find is important for two reasons at once. It extends the catalog of extremely ancient stars and strengthens the idea that the Milky Way’s oldest stellar inhabitants may include immigrants from other galactic systems. In effect, the star becomes both a chemical fossil and a witness to galactic mixing.

A reminder of what big sky surveys can enable

The discovery also highlights the continuing scientific value of survey infrastructure. The Sloan Digital Sky Survey has spent decades collecting spectra of millions of objects across the sky, and the current SDSS-V phase continues that work with observatories in both hemispheres. That broad coverage makes it possible not only to answer planned research questions but to give students access to datasets rich enough for real discovery.

That educational angle is more than a feel-good detail. It shows how modern astronomy increasingly depends on large, open-ended data systems that can be used by many kinds of investigators, from senior researchers to students in a university field course. The bottleneck is not simply access to telescopes; it is the ability to identify rare objects hidden inside enormous catalogs.

In this case, that process appears to have worked exceptionally well. Students screened several thousand candidates, selected a much smaller set for closer attention, and then captured an object with unusually strong scientific value. The result is a reminder that discovery in astronomy often comes from patient filtering as much as from headline-grabbing instruments.

What scientists may learn next

Even from the limited material provided, the next stage is easy to see. An object this metal-poor invites more detailed study of its chemistry, motion, and origin. Researchers will want to understand exactly how it fits into the early history of star formation and how confidently it can be linked to an external galaxy.

Whatever those follow-up results show, SDSS J0715-7334 already represents a notable find. It is a rare example of how a single star can touch several of astronomy’s biggest themes at once: the aftermath of the first stars, the chemical evolution of the universe, and the long merger-driven growth of the Milky Way.

Key points

  • University of Chicago undergraduates identified SDSS J0715-7334 using Sloan Digital Sky Survey data.
  • The star is described as extremely metal-poor, with only 0.005% of the metals found in stars like the Sun.
  • Researchers say it is one of the oldest known stars and likely originated outside the Milky Way.
  • The finding links early-universe chemistry with the Milky Way’s history of absorbing smaller galaxies.

This article is based on reporting by Universe Today. Read the original article.