How a Star Expands

Well, everyone, look who’s back!

For those of you who are not signed up for my newsletter, I’m sorry I’ve been away forever—life happened. It’s been a very rough three months. I hope you’re all doing well in light of the COVID-19 pandemic. I know it’s pretty tough right now, but we’ll pull through. Hang in there! 🙂

And now, for some long-awaited astronomy…

Meet Betelgeuse, a bright star in the winter constellation Orion.

Betelgeuse is a cool red supergiant that we’ll talk about a lot more in just a couple weeks, when we cover variable stars. Not too long ago, it was the height of excitement among astronomers. No one was sure why it…well…appeared to be dimming.

Yeah. Like a lightbulb. It was literally getting fainter—considerably fainter.

It’s pretty normal for Betelgeuse, like any other variable star, to fluctuate in brightness over time, but it was doing something downright weird. We’ll explore what was going on with it soon enough.

For now, let’s take a look at why Betelgeuse, as a supergiant, is so darn big.

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What Goes On Inside a Star?

Our sun is undoubtedly the star we know the best. It’s only 93 million miles away—which might seem far, but isn’t that large a distance when you realize that the nearest neighboring star is a whole 4.3 light-years away.

As in, it takes light—yeah, that same stuff that hits the ground from your flashlight in a split second—a whole 4.3 years to get here.

We’re pretty familiar with our star’s interior. We know it produces most of its energy in its core, a relatively small but very hot region at its center. We also know that energy then radiates outward until it hits the convective layer.

There, the energy gets stuck in circulation for a bit until it finally manages to leave the sun’s surface.

But…how normal is that? Is it the same for all stars, or just the sun?

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Energy Flow from the Sun’s Core

wind and water.jpg

Ask any climate scientist how we should power our world without fossil fuels, and they’re bound to tell you about wind and solar power.

You might be surprised to know that both of these come from the sun. Solar panels collect the sun’s energy directly, but we wouldn’t even have wind if not for the sun.

Why? Because in order to move, you need energy. And not just you. I’m talking about every speck of material on Planet Earth that shifts an inch. It’s because it has energy.

That energy can come from a lot of places. Earth is still a dynamic world with a hot interior, but it’s not hot enough to sustain all the life and other movement on its surface. A lot of our planet’s energy comes from the sun.

But here’s the big question. How the heck does it get here? Continue reading