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 😉
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.
Way back when we spent a number of posts surveying the stars, we covered binary systems. These are star systems that contain multiple stars. Imagine if our sun had a companion, and two stars rose and set in our sky over the cycle of day and night.
It might surprise you that the majority of stars in the universe are actually in binary systems. Our solar system seems to be an outlier in that regard. Most stars have a companion or two or six…
…and so do some neutron stars.
Remember that neutron stars are the collapsed remnants of massive stars that have gone supernova. If most stars are part of binary systems, then naturally, some of these stars will evolve into neutron stars and still be part of their birth system.
Astronomers have discovered that the clouds of gas and dust—the interstellar medium (ISM)—found between the stars are made of the same materials as the stars themselves. In fact, hydrogen is the most common element in both stars and the ISM, followed closely by helium.
But it would be more accurate to say that stars are made of the same material as the ISM, not the other way around.
This is because all of the stars formed out of material in the ISM at some point millions to hundreds of billions of years ago. And when they die, they return that material—what’s left of it—to the ISM.
Welcome to my first “Science Answers” post! About a month ago, I sent out a post requesting science questions from all of you; you can find it here. This post addresses the first of the questions I was asked. If you have a question, you can ask it in the comments here or on that post, or ask it in an email. Or find me on Facebook!
And by the way…I do apologize for getting this post out so late. But here you are.
Q: What is magnetism? And what’s the difference between electromagnetism and the “magnetism” found in minerals? (asked by Simon)
So…let’s start with something most of us are familiar with.
Can I just say, I’ve never seen a fridge with so many magnets?
Usually, the magnets in our lives serve practical purposes. In your typical household, these fridge magnets would be used to hold up notes, photos, recipes, etc. that you’d want to display in your kitchen.
(Of course, magnet collecting is a perfectly reasonable hobby, if the sheer variety on this fridge is any indication.)
Magnets are something we take for granted. But they are even more a part of our lives than we realize.
When you hear the word “weather,” you probably think of clouds and lightning bolts and rainstorms. Maybe, if you live in particularly high elevation or latitude, you think snowstorms or even blizzards.
We humans are used to these weather patterns. They’re the norm here on Earth. But would you be surprised to hear that the sun has weather of its own?
The sun doesn’t have clouds. Electricity doesn’t crackle through its atmosphere and build up as lightning. Its surface sits comfortably at about 5800 K, which is 9980°F and 5526°C—so it doesn’t even get close to cold enough for rain or snow.
Galileo was the classical astronomer who made the drawing above. I have little idea what his writing actually says—it’s in Latin—but it’s clear enough what this early diagram is all about.
It’s a drawing of his observations of the sun.
And it’s proof, discovered way back in Galileo’s time but not accepted until much later, that the sun actually rotates.
Have you ever looked at the sun, and seen something like this?
Now, before you decide to look at it right now and see what you see, it’s my responsibility as an amateur astronomer to remind you of the safety risks. Focusing your eyes on the sun is dangerous—there’s a reason our eyes automatically flinch away.
How dangerous, you ask? Dangerous enough to burn and even scar your retinas, permanently damaging or even destroying your vision.
Yes, I’m serious.
Now, all this is not to turn you off solar observing entirely. There are safe—and cheap—ways to look at the sun, and see its spots.
When we observe our sun’s corona, we discover something odd.
It’s really, really hot.
But…wait a second. How is that odd? Shouldn’t the sun be hot?
Well…yes. It should, and it is. Its surface temperature is almost ten thousand degrees Fahrenheit, and its core is many times hotter. But there’s a basic law of physics that says energy flows from hotter regions to cooler regions.
The core and photosphere (the visible surface) follow this rule. Even the chromosphere, the lower atmosphere, does as it’s told. But the corona is made up of gases that are hotter than the chromosphere.
Cosmos at Your Doorstep 