🔭 Here is the purest star ever observed

A star of exceptional purity has just been discovered in the Large Magellanic Cloud. With only 0.005% metals compared to the Sun, it is the "cleanest" ever observed. Its existence indicates that it formed shortly after the very first stars.

This red giant, named SDSS J0715‑7334, originates from the Large Magellanic Cloud, a dwarf galaxy interacting with our Milky Way. Its orbit shows that it is migrating from the outer halo of the dwarf galaxy. Researchers have nicknamed it the "Ancient Immigrant" because of this migration. Its age dates back to the first hundreds of millions of years after the Big Bang.

Chemical analysis reveals that SDSS J0715‑7334 was contaminated by the debris of a supernova from a first-generation star, known as Population III. This parent star, at least thirty solar masses, exploded in a particularly energetic manner.

This direct link to a Population III star is unprecedented. No known star has a composition as close to that of primordial stars. Astronomers think that Population III stars were massive and short-lived, making direct observation impossible today. SDSS J0715‑7334 therefore opens a window into that bygone era.

The discovery in the Large Magellanic Cloud indicates that dwarf galaxies may harbor a higher proportion of ultra‑metal‑poor stars. Unlike the Milky Way, these galaxies experienced late star‑formation activity. Their chemical isolation preserved almost pristine gases, conducive to the birth of stars like SDSS J0715‑7334.

Surveys from the Sloan Digital Sky Survey (SDSS) made it possible to identify this star among millions. Thanks to the Magellan spectrograph in Chile, researchers accurately measured its composition. The study of SDSS J0715‑7334, published in Nature Astronomy, marks a step toward understanding the first stellar generations.