They were made of hydrogen and helium only, without any heavy elements. The first stars were so massive that it is believed none of them have survived until today. Their smaller descendants could be still alive today, even if they were born. They would be recognizable by their very low metalities or the proportions of heavier than helium elements that are associated with them.
Scientists, among them a group of students from the University of Chicago’s undergraduate program, have discovered what is believed to be the universe’s most chemically pure star. SDSS J07157334 shines in the Large Magellanic Cloud’s halo, and the star’s elemental composition tells the story of more than 13 billions years.
It is located about 80,000 miles away. Observations indicate that the star is from the beginning of the universe.
The star formed before the Earth or our Sun in the early billions of years following the Big Bang.
This discovery offers an unique look at the evolution of stars from the very beginning of time, especially their transition from large to small stars.
When were the first stars born in the Universe?
Alexander Ji is an assistant professor at the University of Chicago and first author for the study. These pristine stars provide a window into the beginning of galaxies and stars in the Universe.
This star’s iron content is [Fe/H] Carbon levels even lower than -4.3%[C/Fe] Its total metallicity (-0.2) is below 7.8 x 10- 7, making it ten times cleaner than even the oldest galaxies observed so far by the James Webb Space Telescope.
The team found that it was the oldest known star, by far.
It had only half the number of heavy elements, compared to its previous record-holder. The team also discovered that it was a galactic immigrant star, which originated elsewhere and is now being drawn into the Milky Way.
Chemical fingerprints reveal that the star was enhanced by a supernova from an old star with a mass about 30 times greater than the Sun.
This early explosion was responsible for spreading the first heavy elements throughout the universe. Some of this material went on to form the modern star.
The orbit of this satellite confirms it to be a part of the Large Magnellanic Cloud.
This is a satellite galaxie of our Milky Way. It is one of the most rare finds and a fossilized living record of chemical enrichment in the early universe.
Scientists have discovered the earliest signs of hydrogen in our universe
This discovery explains why stars of later generations are smaller than those from the beginning. The scientists had previously proposed two theories, one involving the presence of heavier elements and the other relating to cosmic dust particles (such as silicates or soot).
Pierre Thibodeaux is a UChicago graduate student and co-author of the study. Dust is all over the place now.
We weren’t certain if dust existed then. Dust could have caused the gas to fragment, resulting in several small stars rather than one large star.
Natalie Orrantia is a College fourth-year student. Scientists can now narrow down their search to find similar stars, once they have found this star. It’s great that we have found this early star. But the more stars you discover, the better you can explain how the universe developed.
Journal Reference
- Ji, A.P., Chandra, V., Mejias-Torres, S. The et all The Large Magellanic Cloud has produced a star that is almost pristine. Nat Astron (2026).
DOI: 10.1038/s41550-026-02816-7
