Charting their Growth through Mergers and Acquisitions
I remember an astronomy class I took back in the early 1990s called “Topics in Stars and Galaxies.” At that time, HST had just been launched (or was about to be), and so astronomers didn’t have the nice, clean deep images of the early universe that HST and other facilities give us these days. One of the topics we discussed was the evolution of galaxies, and I remember someone in the class asking “So, how did galaxies get started?” The professor’s answer was, essentially, “good question.” It wasn’t meant flippantly — it was a good summary of what the future held for folks (like me) who are interested in the formation of galaxies.
Today, some twenty years later, we know a lot more about the early universe and the early epochs of galaxy creation, and can track some of the early “seeds” of galaxies back to little shreds of light that we think combined to become larger galaxies. The hierarchical model of galaxy evolution actually proposes that big galaxies from little galaxies grow (through mergers and interactions). That’s not the entire story, of course, but there is a LOT of interest in the physics and mechanics of those mergers and interactions.
The Milky Way itself was built that way, and is, in fact, still ingesting some dwarf galaxies today. Astronomers using a variety of instruments have seen distinct streams of stars that were not born in the Milky Way, but are finding their homes here as a result of a complex dance between the Milky Way and dwarf galaxies. In the future, the Milky Way will do a cosmic dance with the Andromeda Galaxy, an act that will change the shape and makeup of these two galactic cities forever.
Want to know more about these mergers and acquisitions? Head on over to Astrocast.tv, where I’ve created a nice segment of The Astronomer’s Universe called “Galaxy Mergers and Acquisitions” that focuses on how galaxies dance together to grow and evolve.
