Those galaxies orbiting the Milky Way are all lined up in a weird, flat way because of a massive ancient crash.
March 23, 2026
Original Paper
VINTERGATAN-GM: long-lived satellite planes induced by a massive GSE-like merger
arXiv · 2603.20171
The Takeaway
For years, astronomers were stumped because the small galaxies around us are lined up in a neat, flat plane, which contradicts standard models of a random universe. This study shows that a giant crash 10 billion years ago funneled these galaxies into a permanent 'parade' that persists to this day.
From the abstract
Satellite galaxies in the Local Group tend to be distributed in thin, planar configurations, with many sharing coherent orbital motion. Galaxy formation simulations in $\Lambda$CDM have historically struggled to produce similar structures, leading to the so-called "planes of satellites problem". In this work, we investigate whether the emergence of such structures is connected to the mass of a major merger at $z\sim2$, analogous to the Gaia-Sausage-Enceladus (GSE) event in the Milky Way. We use