The Different Shapes of Galaxies

By now, we’ve spent a heck of a lot of time exploring spiral galaxies.

It makes sense–they’re certainly the most photogenic. Seriously. Do me a favor and do a quick Google search for galaxies. When I did, nearly all the results were spirals…even though spirals are not the most common galaxies in the universe.

There is, of course, another reason we’re so familiar with spirals right now. We dipped our toes in the waters of studying galaxies by exploring our own home galaxy–a reasonable starting point. Our Milky Way just happens to be a spiral.

Well…it doesn’t “just happen” to be a spiral. But we’ll get to the reasons for that…

For now, let’s take a dive into all the different types of galaxies.

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The Milky Way Demystified

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!)

Anyway…on to the Milky Way!

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Structure of the Milky Way

In the vast expanse of the cosmos, the Milky Way Galaxy is our home.

You’ve no doubt seen images of the Milky Way and similar galaxies elsewhere online. It’s a large, spiral galaxy, one of the most spectacular galactic shapes. That spiral shape is fairly iconic–and for years, that’s as far as I thought galaxy classification went.

Turns out, galaxies are way more diverse than just the main three classifications I knew about (spirals, ellipticals, and irregulars). The Milky Way is fully classified as an SBbc: a barred spiral galaxy with a medium-sized nucleus.

Spirals are also described as “grand design” (two distinct spiral arms) or “flocculent” (a sort of fluffy appearance); the Milky Way is somewhere in the middle.

But even those classifications and descriptions don’t fully describe our galaxy.

So what exactly is the structure of the galaxy we call home?

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Discovery of the Milky Way

Ever seen this before?

It’s not a sight that most of the developed world gets to see–at least not all the time. Light pollution from major cities completely obscures this view. Even in the suburbs where I live, I can kind of make it out–because I know where to look and what to expect.

The best way to really see it is to head out into the desert. Or the open ocean. Really, any place that’s a bit geographically removed from civilization. Growing up, Joshua Tree National Park was always my go-to for dark skies.

Even on an exceptionally dark night, though, you won’t necessarily see this. You’ll definitely be wowed by the vast, bright sprinkling of stars overhead, more than you ever see under less than ideal conditions. But the image above was taken with a long exposure.

That is, the camera shutter remained open for a while to collect more light for one image than your eyes ever will. You and I pretty much only see one image per moment.

So what is this gorgeous, hazy band, anyway?

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Black Holes: What the Movies Get Wrong

Any of you recognize this?

To those who don’t, it probably looks like a pretty unimpressive, blurry ring. In fact, this is the first ever image of a black hole, taken with an interferometer the size of the Earth.

If you’re a science geek, you’ve no doubt seen tons of artists’ conceptions of black holes on the internet. Most use a great deal of artistic license. Some of my favorite “images” of black holes used to be the ones that look like ripples in the fabric of space. Imagine my disappointment when I realized that’s not the case at all.

Black holes are singularities—infinitely dense places of zero radius with at least 3 M (solar masses) of star stuff—surrounded by an event horizon, inside of which gravity is so strong that even light cannot escape. That’s why it’s called a black hole.

But they are not “holes” in the usual sense. They are not giant space potholes that you can easily stumble into, and you certainly don’t fall into them the same way you would a pothole.

So…what are black holes really like?

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