Milky Way's Dramatic Flip Linked to Ancient Galaxy Collision

WHO:

The Guardian - Researchers from Durham University, led by Kirill Batrakov.

WHAT:

The Guardian - The Milky Way was flipped on its side following a collision with a dwarf galaxy known as the Gaia Sausage.

The Guardian - The collision occurred about 10 billion years ago.

The Guardian - The Milky Way absorbed stars from the Gaia Sausage, which had a mass exceeding 10 billion times that of the sun.

Phys.org - The research indicates that galaxies with slowly rotating stellar halos are more likely to have experienced a major "disk flip."

WHERE:

The Guardian - The findings were presented at the Royal Astronomical Society’s National Astronomy Meeting in Birmingham.

WHEN:

The Guardian - The next major upheaval in the Milky Way is expected to occur in a few billion years when the Large Magellanic Cloud merges with the Milky Way.

WHY:

The Guardian - The collision with the Gaia Sausage fundamentally reshaped the Milky Way, creating the bulge at the center and dominating the stellar halo.

HOW:

The Guardian - Researchers used supercomputer simulations to study the effects of head-on collisions with galaxies like the Gaia Sausage.

The Guardian - The simulations showed that a disc flip likely occurs in galaxies involved in such collisions, taking at least a few hundred million years.

(UPDATED July 21, 2026 19:28 UTC)

Researchers from Durham University, led by Kirill Batrakov, have revealed that the Milky Way was flipped on its side after colliding with a dwarf galaxy known as the Gaia Sausage about 10 billion years ago, an event that fundamentally reshaped our galaxy. This collision, which involved the Milky Way absorbing stars from the Gaia Sausage, created the bulge at the center and influenced the stellar halo, and findings were presented at the Royal Astronomical Society’s National Astronomy Meeting in Birmingham. Looking ahead, the next major upheaval in the Milky Way is anticipated to occur in a few billion years when the Large Magellanic Cloud merges with our galaxy.