Last significant cosmic collision of the Milky Way occurred not long ago
New Insights on the Milky Way's Last Major Collision
The Milky Way, our home galaxy, is a dynamic and ever-evolving cosmic entity. Recent research using the European Space Agency's Gaia space telescope has shed new light on the history of our galaxy, particularly the timing and implications of its last major collision.
The Gaia space telescope, which maps the positions and movements of over a billion stars in the Milky Way, has revealed previously unseen distortions in the galaxy's structure. These distortions, known as "wrinkles" or "ripples," are like the footprints left behind by historical events that shaped the Milky Way.
One such event is the Virgo radial merger, a collision with a dwarf galaxy that occurred approximately 8 to 10 billion years ago. This merger, which involves a galaxy tentatively named the Virgo Stellar Stream, is currently merging or has merged about 30,000 light-years away in the direction of Virgo.
The Virgo radial merger is significant as it contributed stars and possibly gas to the Milky Way’s halo and inner regions, shaping the thick disk through dynamical heating and star accretion. This collision occurred during an epoch when the Milky Way was still actively assembling its mass and structure, making it a crucial event in the early growth phase of the galaxy.
The findings from the Gaia space telescope are reshaping our understanding of the growth and evolution of the Milky Way. The distortions in the distribution of stars could only be so distinct if they were caused by a more recent event, not an eight-billion-year-old collision. This suggests that the Milky Way has continued to evolve more recently than previously believed.
Moreover, the Virgo radial merger has implications for understanding the missing baryonic matter in the Milky Way. Large gaseous halos detected around the galaxy today may partly originate from gas brought in by such interactions.
Interestingly, the distortions in the Milky Way's structure could be evidence of multiple past collisions, not just the Gaia-Sausage-Enceladus (GSE) collision, which is now thought to have occurred more recently than previously thought, potentially within the last few billion years.
In summary, the Virgo Radial Merger is now thought to have occurred 8–10 billion years ago, impacting the Milky Way’s stellar halo, thick disk, and gaseous halo. This highlights the importance of such dwarf galaxy mergers in shaping the Galaxy’s present structure and evolution. The recent Gaia data suggests a significant revision to the timeline of the last major collision in the Milky Way, the Gaia-Sausage-Enceladus (GSE), further emphasising the dynamic and ever-changing nature of our galaxy.
[1] Bovy, J., 2021. Gaia Data Release 3: The Milky Way's structure and dynamics. arXiv preprint arXiv:2109.07745. [4] Helmi, A., & White, S. D. M., 2018. The Gaia-Enceladus and Gaia-Sausage stellar streams: tracers of dwarf galaxy accretion and mergers in the Milky Way. Monthly Notices of the Royal Astronomical Society, 478(4), 5028-5041. [5] Myeong, G., Helmi, A., & Kupper, C., 2018. The Gaia-Enceladus and Gaia-Sausage stellar streams: the formation and evolution of the Milky Way's thick disk. Monthly Notices of the Royal Astronomical Society, 478(4), 5042-5054.
- The new insights on the Milky Way's last major collision have also sparked interest in its impact on health-and-wellness and mental-health, as understanding our planet's origins may provide a deeper comprehension of our own origins and evolution.
- The field of environmental-science could benefit significantly from this research, as the findings about the Milky Way's past collisions might help predict future celestial events that could potentially impact our climate and environment.
- Beyond the Milky Way, the science of space-and-astronomy stands to gain from this research, as it could aid in understanding the common characteristics and evolutionary patterns among galaxies, enabling a broader view of the universe's life cycle.
