Galaxies, Page 86: [Previous Page] [Class Home Page] Textbook pages 434 - 437

Galaxy Evolution and the Role of Mergers

The field of galaxy evolution is concerned with the changes in a galaxy and its components over time. It has become increasingly apparent that 1) Collisions frequently occur between galaxies, expecially in the crowded environments of galaxy clusters, which drastically change the morphology, star formation rate and chemistry in galaxies and 2) Mergers occur, particularly where large galaxies consume smaller galaxies, also called, galactic cannibalism.


Local Mergers There is overwhelming evidence that our galaxy, the Milky Way, has swallowed up a number of smaller dwarf galaxies in the last few billion years. And in fact, in another 5 Billion year, We will MERGE with the Andromeda Galaxy! This may look something like this when it happens:




The Merging of Andromeda with the Milky Way
Computer simulations of this collision are shown here

Clearly, galaxies do not evolve in a pristine environment! Moreover, our Milky Way galaxy contains stars and gas which once belonged in another galaxy, which had a different mass and star formation history. This all has a way of 'muddying' the waters, so to speak, when it comes to understanding the history of our galaxy.