Star Luminosity Classes

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What do you think it would mean for a star to be in a specific luminosity class? I mean…does that mean they go to school to learn how to be bright?

(Ha, ha…yeah, I know, bad astronomy pun.)

Well…not quite.

Stars can be sorted in a lot of ways—and a good thing, too, because there are literally trillions upon trillions of them. Astronomers would be lost if we couldn’t sort them into groups to study.

They can be sorted according to spectral type (composition and temperature), apparent visual magnitude (how bright they look to the naked eye from Earth), and absolute visual magnitude (how bright they would look to the naked eye from ten parsecs away).

They can also be sorted according to their absolute bolometric magnitude (how bright they would look from ten parsecs away if the human eye could see all types of radiation).

And…they can even be sorted according to their luminosity. Continue reading

The Starlight We Can’t See

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Find yourself a dark, unpolluted night sky on a clear night free of clouds, and you are very likely to look up into the heavens and see a sight quite like this. It’s what we see of the Milky Way, our galaxy.

When I’m at an astronomy event with a sky like the one above, I find it absolutely incredible. Do you notice how the stars don’t all look the same?

A couple are startlingly bright, there are numerous stars that are somewhat dimmer, and if you look really hard, you notice that even the dark night background is sprinkled with stars so faint they can barely be seen.

But what if I told you that you’re not even seeing the half of it? Continue reading

What Causes the Lunar Phases?

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We see it almost every night of our lives. For thousands of years, the greatest philosophers and astronomers alike have watched its face change and wondered why.

Step outside and observe the moon every day for a month and you will notice something fascinating. Over the course of the entire month, the moon will go through an entire cycle of phases—no more, no less.

But why?

The phases of the moon are something I’ve talked about before, but I wanted to spend some time on a few common misconceptions this time around and show you the truth behind the lunar phases. Continue reading

The True Brightness of Stars

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Have you ever looked up at the night sky and noticed that while relatively bright stars outline the constellations, there are numerous other stars that are almost too faint to see with the naked eye?

If you ever noticed this, you probably guessed that the brighter stars are literally brighter, and the fainter stars truly are fainter. Or maybe you guessed that they don’t vary in brightness that much, but fainter stars are much farther away.

But that’s not really true…or, at least, it’s not the whole answer.

So what’s the real reason why some stars appear to be brighter than others—and how can we tell how bright they really are? Continue reading

The Sun’s Magnetic Show

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Do you recognize the name Galileo Galilei?

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.

How do we know that? Continue reading

Spots on the Sun

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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.

But what exactly are sunspots?

Continue reading

The Solar Neutrino

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Ever heard of a neutrino?

Well, I guess now you have. But what exactly is a neutrino?

Don’t worry, they’re not harmful. They’re passing through you this very second and you’ll never notice them, not in your whole life. They’ll never hurt you because they just don’t interact with matter—including you—in the way you’d expect.

I’ll bet now you’re wondering where they even come from.

Well, as the diagram illustrates, they come from the sun. They’re kind of a side-effect of the nuclear reaction that powers the sun, and they radiate out from the sun in droves. But that’s not even the coolest bit.

We know how many neutrinos should come from the sun if our theories about its power generation are right. So if we can count them, we can prove those theories correct.

That’s when we encounter a bit of a problem. We can’t actually detect neutrinos.

So how the heck do we count them? Continue reading

Energy Flow from the Sun’s Core

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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

The Proton-Proton Chain

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Take a wild guess: how much energy do you think the sun generates?

Think about it. It definitely generates enough energy to power a world.

Humans depend on the photosynthesis of plants, which converts sunlight into energy. And that’s not all. Without energy from the sun, our atmosphere would behave very differently, and so would our oceans.

Everything that moves on Planet Earth does so because it has energy. And a lot of that energy comes from the sun. It doesn’t even stop there—obviously, the sun has plenty of energy to spare, if the recent influx of solar power means anything.

The sun is incredibly powerful. And it’s powerful enough to keep generating that kind of massive energy supply for billions of years.

So where does it get all its energy? Continue reading