Question: What galaxies have crashed together recently?

Jillian Scudder answered on 15 Jun 2015:

There are at least a few hundred that have finished colliding recently, and probably many more that are harder to find (or are further away- here’s a nearby one http://skyserver.sdss.org/dr7/en/tools/chart/chart.asp?ra=151.83606798&dec=4.07930485 ) – but more fun to think about is that our own galaxy is in the early stages of a collision with Andromeda! We’re pretty sure that this will be the first collision for the Milky Way and Andromeda- our sky will get pretty dramatic in a few billion years, if we’re still around to see it!