Astronomers Discover Universe's Most Pristine Star

SDSS J0715-7334 is a rare second-generation star that formed just billions of years after the Big Bang.

Apr. 4, 2026 at 12:55am

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An abstract, highly structured painting in earthy tones of ochre, sienna, and indigo, depicting sweeping cosmic arcs, concentric circles, and precise botanical spirals, conveying the structural order of the early universe before the formation of heavy elements.A rare glimpse into the dawn of star formation, as astronomers uncover the most pristine celestial object in the known universe.Pasadena Today

An international team of astronomers, led by University of Chicago's Alexander Ji and including Carnegie Observatories' Juna Kollmeier, have discovered the most pristine star in the known universe. The star, named SDSS J0715-7334, is from the second generation of celestial objects that formed just a few billion years after the Big Bang and contains only trace amounts of heavy elements.

Why it matters

Pristine stars like SDSS J0715-7334 provide a unique window into the early universe, revealing how star formation and the production of heavier elements have changed over cosmic time. Studying these rare objects can help astronomers test theories about the first generations of stars and galaxies that emerged after the Big Bang.

The details

The team used data from the Sloan Digital Sky Survey-V (SDSS-V) and observations from the Magellan telescopes at Carnegie Science's Las Campanas Observatory in Chile to identify and confirm SDSS J0715-7334 as the most metal-poor star known, with less than 0.005% of the Sun's metal content. This makes it 40 times more iron-poor than the previous record holder.

  • The discovery was made during an observing trip to Las Campanas by Ji and his undergraduate students from the University of Chicago in spring 2025.
  • The team's findings were published in the journal Nature Astronomy on April 4, 2026.

The players

Alexander Ji

A former Carnegie Observatories postdoctoral fellow and current professor at the University of Chicago, who led the team that discovered SDSS J0715-7334.

Juna Kollmeier

A Carnegie astrophysicist who leads the Sloan Digital Sky Survey-V, a pioneering effort to map the entire sky with millions of optical and infrared spectra.

SDSS J0715-7334

The most pristine star in the known universe, containing only trace amounts of heavy elements and providing a rare glimpse into the early universe.

Sloan Digital Sky Survey-V

The fifth generation of the influential Sloan Digital Sky Survey, which has been a driving force in astronomy for decades.

Magellan Telescopes

The state-of-the-art telescopes at Carnegie Science's Las Campanas Observatory in Chile, which were critical for confirming the properties of SDSS J0715-7334.

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What they’re saying

“These pristine stars are windows into the dawn of stars and galaxies in the universe.”

— Alexander Ji, Professor, University of Chicago

“We have to look in our cosmic backyard to find these objects, because we can't yet observe individual stars at the dawn of star formation. Since these stars are rare, surveys like SDSS-V are designed to have the statistical power to find these needles in the stellar haystack and test our theories of star formation and explosion.”

— Juna Kollmeier, Astrophysicist, Carnegie Science

What’s next

The team plans to conduct further analysis of SDSS J0715-7334 to better understand the early universe and the formation of the first generations of stars.

The takeaway

The discovery of the most pristine star in the universe, SDSS J0715-7334, provides an unprecedented glimpse into the dawn of star and galaxy formation, and highlights the power of collaborative efforts between large-scale sky surveys and specialized observational facilities like the Magellan telescopes.