Astronomers discover the purest star ever found

An ancient immigrant: an artist”s conception (not to scale) of the red giant SDSS J0915-7334, which was born near the Large Magellanic Cloud and has now journeyed to reside in the Milky Way. Credit: Navid Marvi/Carnegie Science

doi.org/10.1038/s41550-026-02816-7
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Astronomers have identified the poorest star in heavy elements ever observed, a true cosmic fossil that allows us to look into the early chapters of the Universe

Called SDSS J0715-7334, it belongs to the second generation of stars, formed a few billion years after the Big Bang, when the cosmos was still very young.

This star is composed almost entirely of hydrogen and helium, with an extremely low amount of “metals”-a term astronomers use for all elements heavier than helium, created by stars over time.

It has less than 0.005% of the Sun’s metal content, only half of what the previous record holder had, and especially low levels of iron and carbon.

In practice, it is 40 times poorer in iron than the poorest iron-rich star known until now.

Located approximately 80,000 light-years from Earth, the star likely originated outside the Milky Way, near the Large Magellanic Cloud, and was later drawn into our galaxy.

Because it formed from nearly pure primordial gas, it preserves the chemical conditions of the early Universe, before the first stars exploded and scattered heavy elements into space.

The discovery was made possible by the Sloan Digital Sky Survey-V (SDSS-V), a large project that maps millions of stellar spectra across the sky.

Initial data came from telescopes in Chile and the United States, and confirmatory observations were made with the Magellan telescopes at the Las Campanas Observatory in Chile.

Using a high-resolution spectrograph, researchers analyzed the star’s light with great precision.

Information from the European Space Agency’s Gaia satellite helped determine its position and origin.

The study, published in the journal Nature Astronomy on April 3, 2026, was led by astronomer Alexander Ji of the University of Chicago, with the participation of Juna Kollmeier and graduate students who experienced the entire process: from data collection to results analysis.

These “pristine” stars act as windows to the dawn of the Universe.

They help us test theories about how the first stars formed, how chemical elements were produced and enriched over time, and how nucleosynthesis occurred shortly after the Big Bang.

Since we cannot directly observe the oldest stars, these rare survivors are our best messengers from the cosmic past.

Finding such a pure star is like discovering a needle in a stellar haystack.

Projects like SDSS-V demonstrate the power of large-scale surveys to reveal exceptional objects and involve the next generation of scientists in the actual discovery process.

This ancient star, a cosmic immigrant now integrated into the Milky Way, continues to tell us the story of how the Universe went from a simple place, made basically of hydrogen and helium, to the rich and diverse cosmos we see today.

Published in 04/08/2026 09h28

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Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.

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