Milky Way Swallowed Dwarf Galaxy Nearly 11.8 Billion Years Ago
Sci.News · 2026-08-18
Astronomers utilizing the NASA/ESA Hubble Space Telescope have uncovered definitive evidence that the young Milky Way absorbed a dwarf galaxy approximately 11.8 billion years ago, just two billion years after the Big Bang, marking one of the earliest major mergers in our Galaxy's history. This event, preceding the 10-billion-year-old Gaia-Sausage-Enceladus merger, involved a dwarf galaxy now named Low-energy-Kraken-Heracles (LKH).
Dr. Davide Massari and his team at the Osservatorio di Astrofisica e Scienza dello Spazio di Bologna analyzed 39 globular clusters using Hubble observations and advanced statistical modeling to ascertain their ages and chemical compositions. Through age-metallicity sequencing, they identified three distinct events: the proto-Milky Way, the Gaia-Sausage-Enceladus merger, and an earlier merger approximately 1.8 billion years prior to the latter. The LKH system, estimated to have had a stellar mass similar to Gaia-Sausage-Enceladus, deposited significant material into the inner regions of the Galaxy. This research highlights that the Milky Way’s early evolution was not solely shaped by internally born stars but also by substantial contributions from external galaxies.
*The full article also explores the methodological details of age-metallicity sequencing and the implications for understanding galactic formation models.*