Pristine star near Milky Way's heart hails from the dawn of time

ESO

Pristine star near Milky Way's heart hails from the dawn of time

Sometimes the best place to hide is in the biggest crowd. That may have been on the mind of a star named SMSS J181609.62-333218.7, which inhabits the Milky Way's central bulge of stars 34,000 light-years from Earth in the constellation Sagittarius and boasts a chemical composition nearly matching the one that prevailed right after the birth of the universe, before stars had created any iron. As astronomers report online today in Naturethe star's iron-to-hydrogen ratio is just 1/9000th the solar value, making it the most pristine star ever found in the galaxy's central bulge and indicating it dates back to a time before most other stars had exploded and spewed iron into space. Moreover, the pattern of chemical elements on the star's surface suggests it arose from a cloud of gas and dust enriched by debris from just one powerful supernova (artist's conception shown, above). Even more pristine stars exist in the Milky Way's halo, but the bulge formed first, so the newfound star is one of the most ancient in the entire galaxy, born just a few hundred million years after the big bang.