Some of them, anyhow:
Using Australia’s SkyMapper Southern Survey, the team identified 475 stars with a [Fe/He] ratio less than one-thousandth that of our Sun. We would expect them to be halo stars, but when the team calculation the positions and orbits of these stars using data from Gaia they found that 11% of them orbit within the galactic plane. Their orbits are also very circular, similar to the orbit of the Sun. This is surprising and goes against predictions of current galactic evolution models.
Large sky surveys of our galaxy are certain to revolutionize our understanding of the Milky Way. As even these early results show, it is clear we still have much to learn.Brian Koberlein, “Some of the Milky Way’s oldest stars aren’t where they’re expected to be” at Universe Today
Much to learn? Good place to begin! The paper is paywalled.