An earlier evaluation of the collision is at http://arxiv.org/abs/0705.1170
The Collision Between The Milky Way And Andromeda
T.J. Cox, Abraham Loeb (Harvard/CfA)(Submitted on 8 May 2007 (v1), last revised 20 Feb 2008 (this version, v2))
- 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
