Researchers from the Massachusetts Institute of Technology have discovered the three oldest stars in the Universe, which are located near the Milky Way. This was reported in an article published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).
The oldest stars are located in the halo of the Milky Way – a sparse cloud of stars and gas that surrounds the galactic disk. According to the team’s analysis, the three stars formed between 12 and 13 billion years ago. They have been grouped together as SASS (small accreted stellar system), indicating that each star once belonged to a small, primitive galaxy absorbed by the growing Milky Way.
SASS emerged shortly after the Big Bang, which occurred 13.8 billion years ago, when the Universe consisted mainly of hydrogen and helium and very small amounts of other chemical elements, such as strontium and barium. These oldest stars have a similar composition. Therefore, studying SASS could be key to understanding the evolution of ancient ultra-faint dwarf galaxies.
All three stars are located in different parts of the halo, but their distance from Earth is about 30,000 light years (approximately one-third of the diameter of the Milky Way’s disk). Their movement is opposite to the rest of the galaxy’s disk, and combined with their unusual chemical composition, indicates that they did not originally belong to the Milky Way.