Over the course of my last eight posts, we’ve covered just about everything there is to cover about our home galaxy–or, well, at least the basics.

We’ve explored how astronomers first discovered what that incredible, milky stream of dust across the night sky actually is. We’ve followed astronomers like the Herschels and Harlow Shapley as they tried to measure the size of our galaxy.

We’ve covered its structure–a thin disk of spiral arms, surrounded by an enormous, diffuse halo–and how truly massive this great wheel is.

We then explored those spiral arms, where all the youngest stars are–and where stars form in the first place. And we explored the chaotic nucleus at the very center of the galaxy.

Most recently, we delved into the composition of the Milky Way–that is, how much heavy elements its stars contain. We discovered that stellar compositions hint at how old certain parts of the galaxy are.

But there’s one question we haven’t answered yet, and it’s quite possibly the most important one of all.

How did the Milky Way actually become what it is today?

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