Lecture 29: When Galaxies Collide
What happens if two galaxies collide? The average distance between\nbright galaxies is only about 20 times their size, so over the history\nof the Universe (14 Billion years), we expect that most bright galaxies\nwill have had at least one close gravitational encounter with a\nneighboring galaxy. This lecture explores what happens when two\ngalaxies undergo interactions ranging from passing tidal interactions to\nhead-on collisions, all the way to multiple collisions and galaxy\n"cannibalism" in the centers of large clusters. While at first glance\ngalaxy interactions explain rare "peculiar" galaxies, on closer\nexamination we find that galaxy interactions and mergers are central to\nunderstanding the assembly and evolution of galaxies. At the end, we\ntake a speculative look at the distant future 3-4 Billions years hence\nif in fact Andromeda and the Milky Way are on a collision course. \nRecorded 2006 February 15 in 1008 Evans Laboratory on the Columbus campus of \nThe Ohio State University.