- Astronomers discovered evidence of a direct hit from a dwarf galaxy 10 billion years ago that likely flipped the Milky Way.
- The collision resulted in a significant reorientation of the Milky Way's disc, possibly by more than 90 degrees over hundreds of millions of years.
- Researchers used supercomputer simulations to explain the slow rotation of stars in the Milky Way’s halo, linking it to this ancient event.
- The dwarf galaxy responsible for the collision is named 'Gaia Sausage' due to its unusual orbiting pattern.
Discovery of a Major Cosmic Event
Astronomers at Durham University have uncovered evidence that a significant cosmic event occurred about 10 billion years ago, when our Milky Way was struck by a dwarf galaxy. This direct impact is believed to have dramatically altered the structure of the Milky Way, causing its disc to be flipped by more than 90 degrees over an extended period.
The research team used advanced computer simulations to explore how such a collision could affect the Milky Way. Kirill Batrakov, the lead researcher on this project, noted that it likely took at least several hundred million years for the disc flip to occur. The simulations suggest that galaxies like the Milky Way might undergo significant reorientations after merging with larger dwarf galaxies.
The Role of a Dwarf Galaxy
Identifying a dwarf galaxy as the culprit behind the Milky Way's transformation came in 2018, when an international team used data from the European Space Agency’s Gaia mission to map the orbits of stars. The name 'Gaia Sausage' stems from these unusual trajectories, which resembled a sausagelike pattern.
Impact on Milky Way's Structure
This ancient collision significantly shaped the Milky Way, contributing to the formation of its central bulge and dominating the stellar halo. Despite its dwarf status, this galaxy was massive enough to contain over 10 billion times the mass of the sun, including stars, gas, and dark matter.
Upcoming Major Mergers
While the Gaia Sausage represented a major upheaval in our galaxy's history, future mergers are anticipated. One such event involves the Large Magellanic Cloud, a nearby dwarf galaxy that is expected to merge with the Milky Way in several billion years. However, this merger is predicted to have less dramatic consequences compared to the Gaia Sausage collision.
Conclusion
The discovery of this dwarf galaxy and its impact on the Milky Way highlights the dynamic nature of our galaxy's evolution over billions of years. As astronomers continue to study these events, they gain deeper insights into the complex history and future trajectory of our cosmic neighborhood.
Source: The Guardian
Science Daily
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