Recent research provides new clues to solve one of the oldest enigmas about the evolution of the Milky Way. The study suggests that our galaxy would have experienced a significant change in its orientation during its cosmic history, modifying the direction of its galactic disk billions of years ago. This structure houses the largest concentration of stars and constitutes one of the main components of the galaxy. The findings offer a new perspective on the dynamic evolution of the Milky Way. The results were presented this week at the National Astronomy Meeting organized by the Royal Astronomical Society, which took place in the city of Birmingham. During the meeting, researchers presented evidence supporting the hypothesis of this change in orientation that occurred in the remote past. The work seeks to expand knowledge about the processes that shaped the current structure of the galaxy. In addition, it opens new lines of research to better understand its evolution over time.
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What was recently discovered in the Milky Way by the Durham team of scientists?
A team of researchers from Durham University used advanced simulations run on supercomputers to study the evolution of galaxies with characteristics similar to the Milky Way. The analysis revealed that those with slowly rotating stellar halos are more likely to have experienced a “disk flip,” a phenomenon in which the galactic disk changes its orientation by more than 90 degrees over its history. This structure, where most of the stars are concentrated, is responsible for the spiral shape that characterizes our galaxy. The results offer a new explanation for its dynamic evolution.
The study also indicates that the disk is surrounded by an extensive stellar halo, less dense and formed mainly by stars from smaller galaxies that were absorbed through successive cosmic mergers. Observations from the European Space Agency’s Gaia mission had previously shown that this halo rotates at an unusually low speed, a behavior that still puzzled astronomers. To clarify its origin, scientists tracked the evolution of 25 Milky Way-like galaxies for billions of years within the Auriga cosmological simulations project. These results provide new clues about the processes that shaped the current structure of our galaxy.
What are the indications that point to a change in orientation that completely reshaped our galaxy?
The study determined that galaxies with slower-moving stellar halos exhibited two common characteristics during their evolution. The first was related to a large-scale head-on collision with another galaxy, while the second corresponded to a process known as disk inversion, in which the orientation of the galactic structure changes significantly. These findings helped researchers establish a possible connection between both phenomena and the transformation of galaxies over time.
Kirill Batrakov, astronomer and lead author of the research, noted that there is evidence that the Milky Way suffered a massive collision in the past with a galaxy called Gaia-Sausage-Enceladus, also known as the Gaia Sausage. Based on this background, the scientist considers it probable that our galaxy underwent a disk inversion at some point in its history. This discovery could explain some of the current characteristics of the Milky Way and its complex cosmic evolution.
According to experts, why is it important to study our Milky Way and all its matter from within?
The Milky Way represents one of the main sources of study for understanding the evolution of galaxies and analyzing the behavior of dark matter. Although not all galaxies undergo such a profound change in orientation, the possibility that our galaxy experienced a disk inversion offers new clues to understand how other similar systems in the universe formed and transformed. For astronomers, studying the Milky Way from within allows for a level of detail impossible to achieve with other galaxies.
Kirill Batrakov highlighted that our galaxy functions as a natural laboratory for investigating galactic processes and noted that this possible disk flip adds a new element to the history of the Milky Way. Furthermore, the study revealed that the rotation of its stellar halo is linked to the movement of the dark matter halo, indicating that both structures would have evolved jointly. According to the researchers, this relationship would have developed as the galaxy grew through the incorporation of smaller satellite galaxies.
