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The Milky Way and Andromeda galaxies have been on a collision course for billions of years, but the exact outcome of their cosmic encounter has been uncertain. A recent simulation has shed new light on the fate of the two largest galaxies in our local group, suggesting that their destiny is not predetermined and may depend on the influence of smaller galaxies.
According to the study, which was published in The Astrophysical Journal, the chance of a head-on collision between the Milky Way and Andromeda is about 50-50, or a coin flip, within the next 10 billion years. This means that there is an equal likelihood of the galaxies merging into a single entity or avoiding each other and passing by harmlessly.
The researchers used a state-of-the-art computer model to simulate the gravitational interactions of more than 20 million stars and dark matter particles in the Milky Way, Andromeda, and their surroundings. They also included the effects of 13 nearby dwarf galaxies, which are much smaller than the Milky Way and Andromeda but still have a significant gravitational pull.
The results showed that the dwarf galaxies could play a crucial role in determining the fate of the Milky Way and Andromeda. Depending on their positions and velocities, the dwarf galaxies could either attract or repel the two giants, altering their trajectories and preventing or facilitating a collision.
Lead author Marius Cautun, a postdoctoral researcher at Durham University in the UK, said in a press release that the study “highlights the important role of minor mergers in shaping the future evolution of galaxies.” He added that “the fate of the Milky Way and Andromeda depends on the delicate balance between the opposing forces of attraction and repulsion.”
The new simulation challenges previous studies that predicted a certain collision between the Milky Way and Andromeda, based on their relative motion and gravitational attraction. However, those studies did not account for the effects of smaller galaxies, which are more numerous and diverse than previously thought.
The researchers noted that their model was not perfect and had some limitations, such as the simplification of the galaxies’ shapes and the neglect of other factors that could affect their dynamics. They also acknowledged that the simulation did not cover the entire lifespan of the galaxies, which are expected to live for trillions of years.
Nevertheless, the study provides a more nuanced and realistic view of the future of the Milky Way and Andromeda, which are currently about 2.5 million light-years apart and moving towards each other at a speed of about 110 km/s. The collision, if it happens, is likely to trigger a burst of star formation and reshape the structure of both galaxies, but it is not expected to cause any catastrophic events, such as a black hole merger or a gamma-ray burst.
The study also highlights the importance of studying the interactions between galaxies and their environment, as they can reveal the underlying physical laws that govern the evolution of the universe. By refining our understanding of these laws, we can better predict the fate of our own galaxy and the cosmos as a whole.
