The Milky Way was dramatically flipped on its side after a head-on collision with a dwarf galaxy called the Gaia Sausage about 10 billion years ago, astronomers have revealed. This cataclysmic event reshaped our galaxy long before the solar system formed, offering new insights into galactic evolution.
How the Milky Way Flipped After a Galaxy Collision
Using supercomputer simulations, researchers at Durham University found that the Milky Way likely experienced a “disc flip” of more than 90 degrees when it absorbed the Gaia Sausage. The collision tore the dwarf galaxy apart, but the momentum caused the entire disc of the Milky Way to reorient slowly over hundreds of millions of years.
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“It probably takes at least a few hundred million years,” said Kirill Batrakov, lead researcher on the project. The discovery explains a long-standing mystery about the slow rotation of stars in the Milky Way’s halo.
Why Halo Stars Rotate Slowly
Previous data from the European Space Agency’s Gaia mission showed that stars in the Milky Way disc orbit at about 220 km per second, while halo stars circle at just 25 km per second. The simulations revealed that head-on collisions with dwarf galaxies like the Gaia Sausage produce these slow-moving halo stars.
| Star Location | Orbital Speed | Cause |
|---|---|---|
| Milky Way Disc | 220 km/s | Normal rotation |
| Stellar Halo | 25 km/s | Collision-induced disc flip |
Key Takeaways from the Research
- The Milky Way flipped by over 90 degrees after a head-on collision with the Gaia Sausage dwarf galaxy.
- The event occurred about 10 billion years ago, before the solar system existed.
- Supercomputer simulations at Durham University matched the observed slow rotation of halo stars.
- The disc flip took at least a few hundred million years to complete.
FAQ
What caused the Milky Way to flip?
The Milky Way flipped after a head-on collision with the Gaia Sausage dwarf galaxy about 10 billion years ago, according to Durham University simulations.
How long did the Milky Way flip take?
The disc flip likely took at least a few hundred million years to complete, gradually reorienting the galaxy.
Why are halo stars in the Milky Way so slow?
Halo stars orbit at about 25 km/s because the collision and disc flip disrupted their motion, unlike stars in the disc that travel at 220 km/s.
This groundbreaking research sheds light on the violent history of our galaxy and confirms that the Milky Way has been reshaped by cosmic collisions. For more astronomy updates, stay tuned to GrandGoldman.com.