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Milky Way disk flip from Gaia‑Sausage collision

Updated 3 times since CLSTR started tracking revisions of this situation.

What changed

2026-07-27 05:19 UTC → 2026-07-27 18:58 UTC · added removed

Astronomers continue to build evidence have built a growing case that a head‑on merger with an the ancient dwarf galaxy Gaia‑Sausage‑Enceladus reoriented the Milky Way’s stellar disc by over roughly 90 degrees. Early simulations from Durham University simulations showed the Gaia‑Sausage‑Enceladus impact shredded the dwarf, deposited its stars in the halo, halo and caused a gradual disc flip lasting over several hundred million years. A larger suite of 25 Milky Way‑like simulated galaxies confirmed that later linked such frontal mergers can generate to the Galaxy’s unusually slow‑rotating stellar halo and linked to the elongated “Sausage” component to that event. component. British researchers have now used researchers, using the Auriga cosmological simulations of the same 25 analogues to argue analogues, argued that a similar collision, identified as Gaya‑Encel, collision more than 10 billion years ago likely altered the Milky Way’s orientation. Their analysis finds that slowly rotating stellar halos are frequently associated with strong impacts that re‑orient spiral disks, and ties Galaxy’s orientation, tying halo rotation to the surrounding dark‑matter halo. A concurrent study mapping the Galaxy’s farthest reaches with gamma‑ray bursts and X‑ray/radio observations suggests the Milky Way extends well beyond previous size estimates. Durham simulations Recent work presented at a Royal Astronomical Society conference reinforce the possibility 2026 National Astronomy Meeting in Birmingham, led by Kirill Batrakov and collaborators, reinforced these findings. Their analysis of the 25‑galaxy sample confirmed that the massive Gaia‑Enceladus merger tipped slow halo rotation is a hallmark of strong frontal impacts and suggested the disc, disc could have reversed its tilt by up to 90 degrees, reshaping both the Galaxy’s size Sun’s past trajectory and dynamical history. the coupled evolution of the stellar and dark‑matter halos.

Versions

  1. 2026-07-27 18:58 UTC Milky Way disk flip from Gaia‑Sausage collision
  2. 2026-07-27 05:19 UTC Milky Way disk flip from Gaia‑Sausage collision
  3. 2026-07-26 20:38 UTC Milky Way disk flip from Gaia‑Sausage collision
  4. 2026-07-26 08:58 UTC Milky Way disk flip from Gaia‑Sausage collision

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