Will the Milky Way and Andromeda collide or pass through each other?

[Plasma]

I have heard that in about 3 billion years, the Milky Way will collide with the Andromeda galaxy. I have also heard that they won`t actually collide, because the spacing in between the stars is so great. Instead, they will pass through one another with only a handful of stars colliding. Is this true?

 

[yenchin]

The shape of the galaxies will be deformed though. They won't be nice spirals anymore

 

[ranger]

I believe their centers will eventually combine and the two galaxies will become one. They won't simply pass through each other and go their separate ways. Consider this simulation, notice how the galactic centers merge.

 

[yenchin]

And the black holes at the center of both galaxies (if they really do exist) will merge into a larger black hole.

 

[xAbsoluteZerox]

Yes, the two galaxies will combine into one larger galaxy but there will be very few actual collisions between the stars. Eventually, they will reach an equilibrium and thus becoming a new, much larger galaxy.

 

[hellfire]

Also clouds of the interstellar medium will collide and unstabilize leading to star formation. See for example http://hubblesite.org/gallery/album/entire_collection/pr1997034b/.