Proof that the Milky Way experienced a significant merger only 1.5 billion years after the Big Bang

arXiv:2601.18896 · astro-ph.GA · Submitted 2026-08-17 · Read on arXiv

Davide Massari, Chiara Zerbinati, Cristiano Fanelli, Amina Helmi, Edoardo Ceccarelli, Fernando Aguado-Agelet, Santi Cassisi, Ewoud Wempe, Matteo Monelli, Andrea Bellini, Thomas Callingham, Hanneke C. Woudenberg, Roger Cohen, Carme Gallart, Elena Pancino, Sara Saracino, Maurizio Salaris, Alessio Mucciarelli

astro-ph.GA

Submitted: 2026-08-17

Updated: 2026-08-18

Comments: Revised version of a paper under review, 26 pages, 8 figures, 2 tables

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Milky Way — 43× in this paper
• Metallicity — 23× in this paper · explained in 3 episodes
• Abundance — 3× in this paper · explained in 1 episode
• Clustering — 1× in this paper · explained in 2 episodes
• Consistency — 1× in this paper · explained in 3 episodes
• Core — 1× in this paper · explained in 2 episodes
• Fidelity — 1× in this paper · explained in 2 episodes
• Maximum A Posteriori — 1× in this paper
• Stellar Feedback — 1× in this paper · explained in 2 episodes
• alpha — 1× in this paper · explained in 1 episode

Sources

• Birth of the Galactic Disk Revealed by the H3 Survey
• Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) II. Unveiling the formation and evolution of the kinematically selected Thick and Thin Discs
• Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) IV. Chrono-dynamics of seven old star clusters in the Large Magellanic Cloud and the peculiar origin of NGC 1841

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