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Milky Way Flipped by Ancient Galaxy Smash
21 Jul
Summary
- Galaxy was struck by the Gaia Sausage 10 billion years ago.
- Collision likely flipped the Milky Way's disc over 90 degrees.
- Simulations confirm a head-on impact caused the galaxy flip.
Approximately 10 billion years ago, the Milky Way galaxy underwent a dramatic transformation due to a head-on collision with an incoming dwarf galaxy, the Gaia Sausage. This cataclysmic event, occurring long before the solar system's formation, caused the Milky Way to tear apart and absorb its smaller companion.
New supercomputer simulations by Durham University researchers suggest this impact likely flipped the entire disc of the Milky Way by over 90 degrees, settling it into its present position. This process would have taken several hundred million years.
The collision was initially uncovered by studying the surprisingly slow rotation of stars in the Milky Way's halo. Simulations showed that galaxies experiencing such a head-on strike typically develop slower-moving halo stars, explaining the observed phenomenon. The Gaia Sausage's stars, gas, and dark matter amounted to over 10 billion times the Sun's mass. Future galactic upheavals include mergers with the Large Magellanic Cloud and the Sagittarius dwarf galaxy, though these are expected to be less impactful than the ancient Gaia Sausage collision.
