Milky Way Galaxy may not clash with Andromeda

For more than a century it has been a textbook knowledge that our Milky Way Galaxy is doomed to collide with another large spiral galaxy, Andromeda, in the next 5 billion years and merge into one even larger Milky Way. But a new analysis published in the magazine Nature Astronomy has been throwing that long -standing story into a more uncertain light. The authors conclude that the chance of this collision and merger is closer to the chances of a coin flip, with a probability of about 50 percent that the two galaxies will prevent such an event during the next 10 billion years.

Both the Melkweg and the Andromeda star systems (M31) are part of what is known as the local group (LG), which also houses other smaller galaxies (some not yet discovered) as well as dark matter (according to the prevailing standard cosmological model). Both already have remains of mergers from the past and interactions with other galaxies, according to the authors.

“Predicting future mergers requires knowledge about current coordinates, speeds and masses of the systems participating in the interaction,” the authors wrote. This not only includes gravity between them, but also dynamic friction. It is the latter that dominates when galaxies are on their way to a merger, because it ensures that galactic jobs are dropped.

This latest analysis is the result of combining data from the Hubble Space Telescope and the Gaia Space Telescope of the European Space Agency (ESA) to perform 100,000 Monte Carlo computers simulations, taking into account not only the Melkweg and Andromeda but the full LG system. These simulations yielded a very different prediction: there is about a 50/50 chance that the galaxies will collide within 10 billion years. There is still a 2 percent chance that they will clash for the next 4 to 5 billion years. “Based on the best available data, the fate of our Milky Way is still fully open,” the authors concluded.