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Revised Simulations Show 50% Chance of Milky Way-Andromeda Collision Over Next Ten Billion Years

Incorporating the Large Magellanic Cloud’s gravitational pull into updated telescope observations yields only a 2% probability of collision within five billion years.

Three images show different scenarios for how the Milky Way and Andromeda galaxies could interact in the future. At top left, two spiral galaxies pass each other at a large distance. At top right, two spiral galaxies are closer together, their invisible gas halos interacting. The bottom image shows the collision of two spiral galaxies, resulting in an X-shaped patch.
Image
Image: NASA/JPL-Caltech

Overview

  • Researchers ran 100,000 Monte Carlo simulations using updated Gaia and Hubble data to chart the Local Group’s evolution across ten billion years.
  • Models include the effects of the Large Magellanic Cloud and Andromeda’s satellite M33 to capture a broader range of gravitational interactions.
  • Only 2% of scenarios predict a head-on collision within five billion years, with most runs showing a distant flyby exceeding half a million light-years.
  • In over half the simulations dark-matter friction during close encounters slows both galaxies enough to merge in eight to ten billion years.
  • Upcoming Gaia mission releases promise more precise measurements of galaxy motions and masses to narrow remaining uncertainties.