Story perspectives

Milky Way Disc Flipped 90° After Gaia-Sausage Collision

7/23/2026

Summary

Story summary

Kirill Batrakov and his Durham University team presented evidence that the Milky Way’s disc flipped over 90 degrees after a head-on merger with Gaia-Sausage-Enceladus.
Auriga simulations of 25 Milky Way-like galaxies showed the slowest stellar haloes (?10–20 km/s) result from such mergers and disc-flip events.
The authors say a disc flip would have reshaped stellar orbits, altering the Sun’s path, and that the Milky Way’s dark-matter halo rotates slowly and appears twisted.

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Story summary

Kirill Batrakov and his Durham University team presented evidence that the Milky Way’s disc flipped over 90 degrees after a head-on merger with Gaia-Sausage-Enceladus.
Auriga simulations of 25 Milky Way-like galaxies showed the slowest stellar haloes (?10–20 km/s) result from such mergers and disc-flip events.
The authors say a disc flip would have reshaped stellar orbits, altering the Sun’s path, and that the Milky Way’s dark-matter halo rotates slowly and appears twisted.