The Ancient Roots of the Milky Way’s Disks: Evidence for Early Co-Formation Before a Galactic Collision
Borbolato et al. find that the Milky Way’s thin and thick disks began forming over 11 billion years ago, earlier than previously thought. Using stellar ages and chemistry from APOGEE, LAMOST, and Gaia data, they show both disks co-formed, challenging models that rely on a major merger to start thin disk formation. Instead, the Gaia-Sausage Enceladus event likely halted thick disk growth and boosted thin disk star formation.
Investigating the Milky Way’s Thin Disk Evolution Through Solar Twins
The study by Anastasiia Plotnikova investigates the chemical evolution of the Milky Way’s thin disk by analyzing solar twins—stars similar to the Sun. Using high-resolution spectroscopy, the team examined the age-metallicity relationship (AMR) and found no evidence for a split into distinct populations, challenging previous studies. They suggest that radial migration and galaxy mergers, like the Gaia-Enceladus/Sausage event, significantly shape the disk’s chemical composition, indicating a more continuous, smooth evolution of the thin disk than previously thought.