A trio of ancient stars found right here in our own Milky Way could be some of the oldest stars in the Universe.
The earliest stars were mostly made of hydrogen and helium, as this was all that was created during the Big Bang.
These stars produced heavier elements, which were then incorporated into subsequent generations of stars.
The amount of heavy elements within this trio indicates they must have formed around 12–13 billion years ago, soon after the Big Bang.
The stars are also moving very quickly and in the opposite direction to most other stars in our Galaxy.
This indicates they started life outside the Milky Way, probably in primitive dwarf galaxies that later fell into our own.
Though some of these dwarf galaxies still exist today, they are too faint to be studied in detail.
The team behind the study have called the stars 'SASS', meaning Small Accreted Stellar System stars, because it seems each star once belonged to its own small galaxy that was later absorbed by the Milky Way.
"Now we can look for more analogues [stars like these] in the Milky Way that are much brighter and study their chemical evolution without having to chase these extremely faint stars," says Anna Frebel from MIT who led the study.
"They’re part of our cosmic family tree. And we now have a new way to find them."
Read the full paper at academic.oup.com/mnras/article/530/4/4712/7667655
