Active Galaxies Demystified

Active galaxies are, without a doubt, absolutely spectacular.

Though rare, they tell a critical part of the story of galaxies–and of the universe as a whole. And we’ve spent the last few posts exploring them in depth.

But I know they can also be a bit perplexing. These are some of the most powerful and violent objects in the universe; it comes with the territory!

So, let’s boil this down to the basics and tie it all together. And let’s try not to get caught in a supermassive black hole in the process 😉

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How Supermassive Black Holes Work

We first took a peek at supermassive black holes back in our discussion of galaxies. But now that we’ve covered a few types of active galaxies, it’s time to take a deeper dive.

Okay, I guess we won’t really be diving into a black hole…sorry to disappoint!

(Honestly, though, you really wouldn’t want to. It would be very uncomfortable, to say the least…and, of course, it’s a one-way trip.)

Supermassive holes are thought to lie at the hearts of most galaxies, including our own. They seem to be key to galactic structure. Most of them–including our own–are quiet. But a few percent of the galaxies in the universe emit titanic amounts of energy from their nuclei, and supermassive black holes are the ultimate culprit.

But how?

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Exploring Radio Lobes

Meet galaxy NGC 5128, also known as Centaurus A.

Anyone notice something weird going on here?

If you’ve been following my recent posts on galaxies, you might notice that this does not look like a typical galaxy. It has a clear dust band, so it can’t be an elliptical; elliptical galaxies have no obvious dust or gas. But it doesn’t look much like a spiral, either: it has a bright, spherical cloud of stars you’d more expect from an elliptical!

And it’s definitely not an irregular galaxy. It definitely has a disk shape, and irregulars are not disk galaxies.

So what the heck is going on with this galaxy?

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