The Collision Between The Milky Way And Andromeda

TL;DR

Using advanced simulations, this study predicts the Milky Way and Andromeda will collide in a few billion years, potentially affecting the Sun's orbit and resulting in an elliptical galaxy-like remnant.

Contribution

First detailed N-body/hydrodynamic simulation forecasting the future collision and merger of the Milky Way and Andromeda galaxies based on current observational data.

Findings

Galaxies are likely to collide within a few billion years.

The Sun may be displaced into tidal tails or outer halos during the merger.

The merger remnant resembles an elliptical galaxy.

Abstract

We use a N--body/hydrodynamic simulation to forecast the future encounter between the Milky Way and the Andromeda galaxies, given current observational constraints on their relative distance, relative velocity, and masses. Allowing for a comparable amount of diffuse mass to fill the volume of the Local Group, we find that the two galaxies are likely to collide in a few billion years - within the Sun's lifetime. During the the interaction, there is a chance that the Sun will be pulled away from its present orbital radius and reside in an extended tidal tail. The likelihood for this outcome increases as the merger progresses, and there is a remote possibility that our Sun will be more tightly bound to Andromeda than to the Milky Way before the final merger. Eventually, after the merger has completed, the Sun is most likely to be scattered to the outer halo and reside at much larger radii (>30 kpc). The density profiles of the stars, gas and dark matter in the merger product resemble those of elliptical galaxies. Our Local Group model therefore provides a prototype progenitor of late--forming elliptical galaxies.