Alright, people…time to finish off our exploration of the Milky Way Galaxy, our home in the cosmos!
For the past nine weeks, we’ve covered everything from how our galaxy was “discovered” to how it may have formed. But there’s so much more to explore–and, starting next week, we’ll begin covering the vast universe of galaxies beyond our own!
But before we do that…I want to wrap up our discussion of our own galaxy with an overview to tie the last nine posts together.
(By the way, has anyone noticed I actually managed to chug out a post a week for the entire Milky Way “module”? I’m a bit impressed with myself for that!)
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.
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?
We could even build on that, and say that the thin disk is where all the youngest stars are found. We could say that within the thin disk are spiral arms, where the star formation actually happens. We could say that the oldest stars are found in the central bulge and the halo, where there is very little dust and gas to make new stars.
But…what about its chemical composition? If we could explore our galaxy and bring home test tubes of “star stuff,” what would we find? And what can that tell us about our galaxy’s history?
Back in August—sorry I took so long!—we talked about the helium flash, an explosion that occurs within stars when helium nuclei begin to fuse within a degenerate core.
So…this is not what the helium flash would look like.
Even though it’s a powerful explosion, it happens in such a small region in the center of the star that we wouldn’t see it at all, and the star’s outer layers absorb most of the energy from the explosion. I just thought it was a cool picture 🙂